feat(esp_libc): make picolibc default libc

CMakeLists.txt

@@ -78,11 +78,22 @@ else()
     list(APPEND cxx_compile_options "-fno-exceptions")
 endif()
 
-if(CONFIG_COMPILER_CXX_RTTI)
+if(CONFIG_IDF_TOOLCHAIN_GCC)
+    if(CONFIG_COMPILER_CXX_RTTI)
+        idf_toolchain_remove_flags(CXX_COMPILE_OPTIONS "-fno-rtti"
+                                   LINK_OPTIONS "-fno-rtti")
+    else()
+        idf_toolchain_add_flags(CXX_COMPILE_OPTIONS "-fno-rtti"
+                                LINK_OPTIONS "-fno-rtti")
+    endif()
+    idf_toolchain_rerun_abi_detection()
+else() # TODO IDF-14338
+    if(CONFIG_COMPILER_CXX_RTTI)
         list(APPEND cxx_compile_options "-frtti")
-else()
+    else()
         list(APPEND cxx_compile_options "-fno-rtti")
         list(APPEND link_options "-fno-rtti")        # used to invoke correct multilib variant (no-rtti) during linking
+    endif()
 endif()
 
 if(CONFIG_COMPILER_SAVE_RESTORE_LIBCALLS)

Kconfig

@@ -772,6 +772,5 @@ mainmenu "Espressif IoT Development Framework Configuration"
             - CONFIG_ESP_WIFI_EAP_TLS1_3
             - CONFIG_ESP_WIFI_ENABLE_ROAMING_APP
             - CONFIG_USB_HOST_EXT_PORT_RESET_ATTEMPTS
-            - CONFIG_LIBC_PICOLIBC
             - CONFIG_GDMA_ENABLE_WEIGHTED_ARBITRATION
             - CONFIG_I3C_MASTER_ENABLED

components/bt/common/osi/include/osi/pkt_queue.h

@@ -10,6 +10,7 @@
 #include "sys/queue.h"
 #include <stdint.h>
 #include <stdbool.h>
+#include <stddef.h>
 
 #ifdef __cplusplus
 extern "C" {

components/bt/common/tinycrypt/src/ecc.c

@@ -58,6 +58,7 @@
 
 #include <tinycrypt/ecc.h>
 #include <tinycrypt/ecc_platform_specific.h>
+#include <assert.h>
 #include <string.h>
 #include <stdio.h>
 

components/esp_hw_support/include/esp_cpu.h

@@ -224,6 +224,37 @@ FORCE_INLINE_ATTR __attribute__((pure)) void *esp_cpu_pc_to_addr(uint32_t pc)
 #endif
 }
 
+/**
+ * @brief Set the current CPU core's thread pointer
+ *
+ * Sets the thread pointer register to the given value.
+ *
+ * @param threadptr Pointer to the thread-local storage area
+ */
+FORCE_INLINE_ATTR void esp_cpu_set_threadptr(void * threadptr)
+{
+#ifdef __XTENSA__
+    xt_utils_set_threadptr(threadptr);
+#else
+    rv_utils_set_threadptr(threadptr);
+#endif
+}
+
+/**
+ * @brief Get the current CPU core's thread pointer
+ *
+ * @return thread pointer register value
+ */
+FORCE_INLINE_ATTR void *esp_cpu_get_threadptr(void)
+{
+#ifdef __XTENSA__
+    return xt_utils_get_threadptr();
+#else
+    return rv_utils_get_threadptr();
+#endif
+}
+
+
 /* ------------------------------------------------- CPU Interrupts ----------------------------------------------------
  *
  * ------------------------------------------------------------------------------------------------------------------ */

components/esp_libc/CMakeLists.txt

@@ -64,7 +64,11 @@ else()
     list(APPEND srcs
          "src/picolibc/picolibc_init.c"
          "src/picolibc/rand.c"
-         "src/picolibc/open_memstream.c")
+         "src/picolibc/open_memstream.c"
+         "src/picolibc/errno.c")
+    if(CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY)
+        list(APPEND srcs "src/picolibc/getreent.c")
+    endif()
 endif()
 
 set(ldfragments "")

components/esp_libc/Kconfig

@@ -2,15 +2,46 @@ menu "LibC"
 
     choice LIBC
         prompt "LibC to build application with"
-        default LIBC_NEWLIB
+        default LIBC_NEWLIB if IDF_TOOLCHAIN_CLANG
+        default LIBC_PICOLIBC
 
         config LIBC_NEWLIB
             bool "NewLib"
         config LIBC_PICOLIBC
-            bool "Picolibc (EXPERIMENTAL)"
+            bool "Picolibc"
-            depends on !IDF_TOOLCHAIN_CLANG && IDF_EXPERIMENTAL_FEATURES
+            depends on !IDF_TOOLCHAIN_CLANG
     endchoice
 
+    config LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+        bool "Provides limited interoperability with libraries built using Newlib headers"
+        default y
+        depends on LIBC_PICOLIBC
+        help
+            This option provides limited compatibility with libraries built using Newlib headers by:
+
+            Enabling hidden system-header inclusions that exist in Newlib.
+            Adding tls_stdio, tls_stdout, and tls_stderr variables to Thread Local Storage
+            to allow prebuilt libraries to access them via getreent().
+            Providing an implementation of getreent() that returns the value of the thread-pointer register.
+
+            Limitations:
+
+            1. If your application or an external prebuilt library accesses Newlib "struct _reent" implicitly,
+            this may cause memory corruption on the task stack. You have two options:
+
+            - Use libc API calls instead of directly accessing "struct _reent" fields.
+            - Switch ESP-IDF to use the Newlib implementation by setting CONFIG_LIBC_NEWLIB=y in sdkconfig.
+
+            2. If your application uses a prebuilt library built with Newlib headers, you may encounter
+            unexpected behavior when overriding stdin, stdout, and stderr. External prebuilt libraries
+            can only read these streams, so overriding them will not affect as it was for Newlib.
+            You have two options to fix this:
+
+            - Rebuild the library with Picolibc headers that follow POSIX-standardized stdin, stdout,
+              and stderr declarations.
+            - Switch ESP-IDF to use the Newlib implementation by setting CONFIG_LIBC_NEWLIB=y in sdkconfig.
+
+
     config LIBC_MISC_IN_IRAM
         bool "Place misc libc functions (abort/assert/stdatomics) in IRAM" if SPI_FLASH_AUTO_SUSPEND
         default y
@@ -18,7 +49,6 @@ menu "LibC"
     config LIBC_LOCKS_PLACE_IN_IRAM
         bool "Place lock API in IRAM"
         default y
-        depends on LIBC_NEWLIB
         help
             Enable this option to include be able to call the lock API from
             code that runs while cache is disabled, e.g. IRAM interrupts.

components/esp_libc/platform_include/stdio.h

@@ -1,16 +1,24 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 #pragma once
 
+#include_next <stdio.h>
 #include "sdkconfig.h"
 
-#include_next <stdio.h>
+#ifdef __cplusplus
+extern "C" {
+#endif
 
-#if CONFIG_LIBC_PICOLIBC
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+#include <stddef.h>
 void flockfile(FILE *);
 void funlockfile(FILE *);
 FILE *open_memstream(char **, size_t *);
 #endif
+
+#ifdef __cplusplus
+}
+#endif

components/esp_libc/platform_include/stdio_ext.h

@@ -9,6 +9,8 @@
 
 #if CONFIG_LIBC_NEWLIB
 #include_next <stdio_ext.h>
-#else
+#endif
+
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
 #include <stdio-bufio.h>
 #endif

components/esp_libc/platform_include/sys/cdefs.h

@@ -0,0 +1,12 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include_next <sys/cdefs.h>
+#include "sdkconfig.h"
+
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+#include <stdint.h>
+#include <stddef.h>
+#endif

components/esp_libc/platform_include/sys/fcntl.h

@@ -0,0 +1,13 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include "sdkconfig.h"
+
+#include_next <sys/fcntl.h>
+
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+#include <time.h>
+#include <sys/time.h>
+#endif

components/esp_libc/platform_include/sys/time.h

@@ -1,9 +1,13 @@
 /*
- * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 #pragma once
+
+#include "sdkconfig.h"
+
+#if CONFIG_LIBC_NEWLIB
 /* Newlib sys/time.h defines timerisset, timerclear, timercmp, timeradd, timersub macros
    for __CYGWIN__ and __rtems__. We want to define these macros in IDF as well.
    Since we wish to use un-modified newlib headers until a patched newlib version is
@@ -20,3 +24,10 @@
 #define __rtems__
 #include_next <sys/time.h>
 #undef __rtems__
+#else // CONFIG_LIBC_NEWLIB
+#include_next <sys/time.h>
+#endif // CONFIG_LIBC_NEWLIB
+
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+#include <sys/types.h>
+#endif

components/esp_libc/platform_include/sys/unistd.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2018-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2018-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -7,6 +7,11 @@
 #pragma once
 
 #include <sys/types.h>
+#include "sdkconfig.h"
+
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+#include <sys/select.h>
+#endif
 
 #include_next <sys/unistd.h>
 

components/esp_libc/project_include.cmake

@@ -16,6 +16,8 @@ if(CONFIG_IDF_TOOLCHAIN_GCC)
     else()
         idf_toolchain_remove_flags(LINK_OPTIONS "--specs=nano.specs")
     endif()
+
+    idf_toolchain_rerun_abi_detection()
 else() # TODO IDF-14338
     if(CONFIG_STDATOMIC_S32C1I_SPIRAM_WORKAROUND)
         idf_build_set_property(COMPILE_OPTIONS "-mdisable-hardware-atomics" APPEND)

components/esp_libc/sbom.yml

@@ -1,9 +1,7 @@
-name: 'newlib'
+name: 'esp_libc'
-version: '4.5.0'
-cpe: cpe:2.3:a:newlib_project:newlib:{}:*:*:*:*:*:*:*
 supplier: 'Organization: Espressif Systems (Shanghai) CO LTD'
-originator: 'Organization: Red Hat Incorporated'
+originator: 'Organization: Espressif Systems (Shanghai) CO LTD'
 description: An open-source C standard library implementation with additional features and patches from Espressif.
-cve-exclude-list:
+virtpackages:
-  - cve: CVE-2024-30949
+  - sbom_newlibc.yml
-    reason: A vulnerability was discovered in the gettimeofday system call implementation within the RISC-V libgloss component of Newlib. ESP-IDF does not link against libgloss for RISC-V, hence the issue is not directly applicable. Still, the relevant fix has been patched through https://github.com/espressif/newlib-esp32/commit/047ba47013c2656a1e7838dc86cbc75aeeaa67a7
+  - sbom_picolibc.yml

components/esp_libc/sbom_newlibc.yml

@@ -0,0 +1,10 @@
+if: 'LIBC_NEWLIB'
+name: 'newlib'
+version: '4.5.0'
+cpe: cpe:2.3:a:newlib_project:newlib:{}:*:*:*:*:*:*:*
+supplier: 'Organization: Espressif Systems (Shanghai) CO LTD'
+originator: 'Organization: Red Hat Incorporated'
+description: Newlib is a small C standard library for embedded systems
+cve-exclude-list:
+  - cve: CVE-2024-30949
+    reason: A vulnerability was discovered in the gettimeofday system call implementation within the RISC-V libgloss component of Newlib. ESP-IDF does not link against libgloss for RISC-V, hence the issue is not directly applicable. Still, the relevant fix has been patched through https://github.com/espressif/newlib-esp32/commit/047ba47013c2656a1e7838dc86cbc75aeeaa67a7

components/esp_libc/sbom_picolibc.yml

@@ -0,0 +1,6 @@
+if: 'LIBC_PICOLIBC'
+name: 'picolib'
+version: '1.8.10'
+supplier: 'Organization: Espressif Systems (Shanghai) CO LTD'
+originator: 'Organization: keithp.com/picolibc'
+description: C Libraries for Smaller Embedded Systems

components/esp_libc/src/locks.c

@@ -17,9 +17,9 @@
 #include "sdkconfig.h"
 
 #if CONFIG_LIBC_LOCKS_PLACE_IN_IRAM
-#define NEWLIB_LOCKS_IRAM_ATTR IRAM_ATTR
+#define LIBC_LOCKS_IRAM_ATTR IRAM_ATTR
 #else
-#define NEWLIB_LOCKS_IRAM_ATTR
+#define LIBC_LOCKS_IRAM_ATTR
 #endif
 
 /* Notes on our newlib lock implementation:
@@ -50,7 +50,7 @@ static portMUX_TYPE lock_init_spinlock = portMUX_INITIALIZER_UNLOCKED;
    Called by _lock_init*, also called by _lock_acquire* to lazily initialize locks that might have
    been initialised (to zero only) before the RTOS scheduler started.
 */
-static void NEWLIB_LOCKS_IRAM_ATTR lock_init_generic(_lock_t *lock, uint8_t mutex_type)
+static void LIBC_LOCKS_IRAM_ATTR lock_init_generic(_lock_t *lock, uint8_t mutex_type)
 {
     portENTER_CRITICAL(&lock_init_spinlock);
     if (*lock) {
@@ -81,13 +81,13 @@ static void NEWLIB_LOCKS_IRAM_ATTR lock_init_generic(_lock_t *lock, uint8_t mute
     portEXIT_CRITICAL(&lock_init_spinlock);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR _lock_init(_lock_t *lock)
+void LIBC_LOCKS_IRAM_ATTR _lock_init(_lock_t *lock)
 {
     *lock = 0; // In case lock's memory is uninitialized
     lock_init_generic(lock, queueQUEUE_TYPE_MUTEX);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR _lock_init_recursive(_lock_t *lock)
+void LIBC_LOCKS_IRAM_ATTR _lock_init_recursive(_lock_t *lock)
 {
     *lock = 0; // In case lock's memory is uninitialized
     lock_init_generic(lock, queueQUEUE_TYPE_RECURSIVE_MUTEX);
@@ -103,7 +103,7 @@ void NEWLIB_LOCKS_IRAM_ATTR _lock_init_recursive(_lock_t *lock)
    re-initialised if it is used again. Caller has to avoid doing
    this!
 */
-void NEWLIB_LOCKS_IRAM_ATTR _lock_close(_lock_t *lock)
+void LIBC_LOCKS_IRAM_ATTR _lock_close(_lock_t *lock)
 {
     portENTER_CRITICAL(&lock_init_spinlock);
     if (*lock) {
@@ -122,7 +122,7 @@ void _lock_close_recursive(_lock_t *lock) __attribute__((alias("_lock_close")));
 /* Acquire the mutex semaphore for lock. wait up to delay ticks.
    mutex_type is queueQUEUE_TYPE_RECURSIVE_MUTEX or queueQUEUE_TYPE_MUTEX
 */
-static int NEWLIB_LOCKS_IRAM_ATTR lock_acquire_generic(_lock_t *lock, uint32_t delay, uint8_t mutex_type)
+static int LIBC_LOCKS_IRAM_ATTR lock_acquire_generic(_lock_t *lock, uint32_t delay, uint8_t mutex_type)
 {
     SemaphoreHandle_t h = (SemaphoreHandle_t)(*lock);
     if (!h) {
@@ -164,22 +164,22 @@ static int NEWLIB_LOCKS_IRAM_ATTR lock_acquire_generic(_lock_t *lock, uint32_t d
     return (success == pdTRUE) ? 0 : -1;
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR _lock_acquire(_lock_t *lock)
+void LIBC_LOCKS_IRAM_ATTR _lock_acquire(_lock_t *lock)
 {
     lock_acquire_generic(lock, portMAX_DELAY, queueQUEUE_TYPE_MUTEX);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR _lock_acquire_recursive(_lock_t *lock)
+void LIBC_LOCKS_IRAM_ATTR _lock_acquire_recursive(_lock_t *lock)
 {
     lock_acquire_generic(lock, portMAX_DELAY, queueQUEUE_TYPE_RECURSIVE_MUTEX);
 }
 
-int NEWLIB_LOCKS_IRAM_ATTR _lock_try_acquire(_lock_t *lock)
+int LIBC_LOCKS_IRAM_ATTR _lock_try_acquire(_lock_t *lock)
 {
     return lock_acquire_generic(lock, 0, queueQUEUE_TYPE_MUTEX);
 }
 
-int NEWLIB_LOCKS_IRAM_ATTR _lock_try_acquire_recursive(_lock_t *lock)
+int LIBC_LOCKS_IRAM_ATTR _lock_try_acquire_recursive(_lock_t *lock)
 {
     return lock_acquire_generic(lock, 0, queueQUEUE_TYPE_RECURSIVE_MUTEX);
 }
@@ -187,7 +187,7 @@ int NEWLIB_LOCKS_IRAM_ATTR _lock_try_acquire_recursive(_lock_t *lock)
 /* Release the mutex semaphore for lock.
    mutex_type is queueQUEUE_TYPE_RECURSIVE_MUTEX or queueQUEUE_TYPE_MUTEX
 */
-static void NEWLIB_LOCKS_IRAM_ATTR lock_release_generic(_lock_t *lock, uint8_t mutex_type)
+static void LIBC_LOCKS_IRAM_ATTR lock_release_generic(_lock_t *lock, uint8_t mutex_type)
 {
     if (xTaskGetSchedulerState() == taskSCHEDULER_NOT_STARTED) {
         return; /* locking is a no-op before scheduler is up */
@@ -213,12 +213,12 @@ static void NEWLIB_LOCKS_IRAM_ATTR lock_release_generic(_lock_t *lock, uint8_t m
     }
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR _lock_release(_lock_t *lock)
+void LIBC_LOCKS_IRAM_ATTR _lock_release(_lock_t *lock)
 {
     lock_release_generic(lock, queueQUEUE_TYPE_MUTEX);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR _lock_release_recursive(_lock_t *lock)
+void LIBC_LOCKS_IRAM_ATTR _lock_release_recursive(_lock_t *lock)
 {
     lock_release_generic(lock, queueQUEUE_TYPE_RECURSIVE_MUTEX);
 }
@@ -291,69 +291,69 @@ static StaticSemaphore_t s_common_recursive_mutex;
 #define MAYBE_OVERRIDE_LOCK(_lock, _lock_to_use_instead)
 #endif // ROM_NEEDS_MUTEX_OVERRIDE
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_init(_LOCK_T *lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_init(_LOCK_T *lock)
 {
     *lock = NULL;  /* In case lock's memory is uninitialized */
     lock_init_generic(lock, queueQUEUE_TYPE_MUTEX);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_init_recursive(_LOCK_T *lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_init_recursive(_LOCK_T *lock)
 {
     *lock = NULL;  /* In case lock's memory is uninitialized */
     lock_init_generic(lock, queueQUEUE_TYPE_RECURSIVE_MUTEX);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_close(_LOCK_T lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_close(_LOCK_T lock)
 {
     _lock_close(&lock);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_close_recursive(_LOCK_T lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_close_recursive(_LOCK_T lock)
 {
     _lock_close_recursive(&lock);
 }
 
 /* Separate function, to prevent generating multiple assert strings */
-static void NEWLIB_LOCKS_IRAM_ATTR check_lock_nonzero(_LOCK_T lock)
+static void LIBC_LOCKS_IRAM_ATTR check_lock_nonzero(_LOCK_T lock)
 {
     assert(lock != NULL && "Uninitialized lock used");
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_acquire(_LOCK_T lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_acquire(_LOCK_T lock)
 {
     check_lock_nonzero(lock);
     MAYBE_OVERRIDE_LOCK(lock, &s_common_mutex);
     _lock_acquire(&lock);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_acquire_recursive(_LOCK_T lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_acquire_recursive(_LOCK_T lock)
 {
     check_lock_nonzero(lock);
     MAYBE_OVERRIDE_LOCK(lock, &s_common_recursive_mutex);
     _lock_acquire_recursive(&lock);
 }
 
-int NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_try_acquire(_LOCK_T lock)
+int LIBC_LOCKS_IRAM_ATTR __retarget_lock_try_acquire(_LOCK_T lock)
 {
     check_lock_nonzero(lock);
     MAYBE_OVERRIDE_LOCK(lock, &s_common_mutex);
     return _lock_try_acquire(&lock);
 }
 
-int NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_try_acquire_recursive(_LOCK_T lock)
+int LIBC_LOCKS_IRAM_ATTR __retarget_lock_try_acquire_recursive(_LOCK_T lock)
 {
     check_lock_nonzero(lock);
     MAYBE_OVERRIDE_LOCK(lock, &s_common_recursive_mutex);
     return _lock_try_acquire_recursive(&lock);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_release(_LOCK_T lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_release(_LOCK_T lock)
 {
     check_lock_nonzero(lock);
     _lock_release(&lock);
 }
 
-void NEWLIB_LOCKS_IRAM_ATTR __retarget_lock_release_recursive(_LOCK_T lock)
+void LIBC_LOCKS_IRAM_ATTR __retarget_lock_release_recursive(_LOCK_T lock)
 {
     check_lock_nonzero(lock);
     _lock_release_recursive(&lock);

components/esp_libc/src/picolibc/errno.c

@@ -0,0 +1,22 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <errno.h>
+
+/*
+ * Picolibc does not initialize 'errno' and places it in the TBSS section.
+ *
+ * To allow convenient initialization and support interoperability with Newlib,
+ * 'errno' is defined in the TDATA section. The linker script ensures that
+ * it is positioned at the beginning of the TDATA segment.
+ */
+__thread int errno __attribute__((section(".tdata.errno"))) = 0;
+
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+int *__errno(void)
+{
+    return &errno;
+}
+#endif

components/esp_libc/src/picolibc/getreent.c

@@ -0,0 +1,19 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <stdint.h>
+#include "esp_cpu.h"
+
+void *__getreent(void)
+{
+    /*
+     * The linker script provides the basic _reent fields
+     * used to access errno and stdin/stdout/stderr.
+     *
+     * Note: if code accesses other fields in struct _reent
+     * that are not intended to be "public," data corruption may occur.
+     */
+    return esp_cpu_get_threadptr();
+}

components/esp_libc/src/picolibc/picolibc_init.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -33,17 +33,8 @@ static void esp_cleanup_r(struct _reent *rptr)
 #endif
 
 #if ESP_ROM_HAS_RETARGETABLE_LOCKING
-static int __retarget_lock_try_acquire(struct __lock * p)
+int __retarget_lock_try_acquire(struct __lock * p);
-{
+int __retarget_lock_try_acquire_recursive(struct __lock *p);
-    __retarget_lock_acquire(p);
-    return 0;
-}
-
-static int __retarget_lock_try_acquire_recursive(struct __lock *p)
-{
-    __retarget_lock_acquire_recursive(p);
-    return 0;
-}
 #endif
 
 static struct syscall_stub_table s_stub_table = {
@@ -143,20 +134,10 @@ void esp_reent_cleanup(void)
     return;
 }
 
-#if CONFIG_VFS_SUPPORT_IO
+/*
-FILE *stdin;
+ * Initialize stdin, stdout, and stderr using static memory allocation.
-FILE *stdout;
+ * Creating them with fopen() would call malloc() internally.
-FILE *stderr;
+ */
-void esp_libc_init_global_stdio(const char *stdio_dev)
-{
-    stdin = fopen(stdio_dev, "r");
-    stdout = fopen(stdio_dev, "w");
-    assert(stdin);
-    assert(stdout);
-    setlinebuf(stdout);
-    stderr = stdout;
-}
-#else  /* CONFIG_VFS_SUPPORT_IO */
 static char write_buf[BUFSIZ];
 static char read_buf[BUFSIZ];
 
@@ -166,10 +147,28 @@ static struct __file_bufio __stdout = FDEV_SETUP_BUFIO(1, write_buf, BUFSIZ, rea
 FILE *stdin = &__stdin.xfile.cfile.file;
 FILE *stdout = &__stdout.xfile.cfile.file;
 FILE *stderr = &__stdout.xfile.cfile.file;
+
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+__thread FILE* tls_stdin = &__stdin.xfile.cfile.file;
+__thread FILE* tls_stdout = &__stdout.xfile.cfile.file;
+__thread FILE* tls_stderr = &__stdout.xfile.cfile.file;
+#endif
+
+#if CONFIG_VFS_SUPPORT_IO
+void esp_libc_init_global_stdio(const char *stdio_dev)
+{
+    int stdin_fd = open(stdio_dev, O_RDONLY);
+    assert(stdin_fd > 0);
+    __stdin.ptr = (void *)(intptr_t)(stdin_fd);
+
+    int stdout_fd = open(stdio_dev, O_WRONLY);
+    assert(stdout_fd > 0);
+    __stdout.ptr = (void *)(intptr_t)(stdout_fd);
+}
+#else  /* CONFIG_VFS_SUPPORT_IO */
 void esp_libc_init_global_stdio(void)
 {
-    __lock_init_recursive(stdin->lock);
+    /* Nothing to do. */
-    __lock_init_recursive(stdout->lock);
 }
 #endif  /* CONFIG_VFS_SUPPORT_IO */
 

components/esp_libc/src/syscalls.c

@@ -110,6 +110,10 @@ int fcntl(int fd, int cmd, ...)
     return _fcntl_r(__getreent(), fd, cmd, arg);
 }
 
+int getpid()
+{
+    return _getpid_r(__getreent());
+}
 #endif // CONFIG_LIBC_PICOLIBC
 
 void _exit(int __status)

components/esp_rom/CMakeLists.txt

@@ -153,7 +153,7 @@ endif()
 
 if(ESP_TEE_BUILD)
     rom_linker_script("heap")
-    if(CONFIG_ESP_ROM_HAS_NEWLIB_NANO_FORMAT)
+    if(CONFIG_LIBC_NEWLIB AND CONFIG_ESP_ROM_HAS_NEWLIB_NANO_FORMAT)
         rom_linker_script("newlib-nano")
     endif()
     rom_linker_script("libc")

components/esp_rom/esp32/ld/esp32.rom.libc-funcs.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -22,18 +22,12 @@ bzero = 0x4000c1f4;
 div = 0x40056348;
 __dummy_lock = 0x4000c728;
 __dummy_lock_try = 0x4000c730;
-isalnum = 0x40000f04;
-isalpha = 0x40000f18;
 isascii = 0x4000c20c;
 isblank = 0x40000f2c;
 iscntrl = 0x40000f50;
-isdigit = 0x40000f64;
 isgraph = 0x40000f94;
-islower = 0x40000f78;
 isprint = 0x40000fa8;
 ispunct = 0x40000fc0;
-isspace = 0x40000fd4;
-isupper = 0x40000fe8;
 __itoa = 0x40056678;
 itoa = 0x400566b4;
 labs = 0x40056370;
@@ -49,19 +43,15 @@ memset = 0x4000c44c;
 qsort = 0x40056424;
 __sccl = 0x4000c498;
 setjmp = 0x40056268;
-strcasecmp = 0x400011cc;
 strcasestr = 0x40001210;
 strcat = 0x4000c518;
 strchr = 0x4000c53c;
 strcmp = 0x40001274;
-strcoll = 0x40001398;
 strcpy = 0x400013ac;
 strcspn = 0x4000c558;
 strlcat = 0x40001470;
 strlcpy = 0x4000c584;
 strlen = 0x400014c0;
-strlwr = 0x40001524;
-strncasecmp = 0x40001550;
 strncat = 0x4000c5c4;
 strncmp = 0x4000c5f4;
 strncpy = 0x400015d4;
@@ -70,10 +60,7 @@ strrchr = 0x40001708;
 strsep = 0x40001734;
 strspn = 0x4000c648;
 strstr = 0x4000c674;
-strupr = 0x4000174c;
 __submore = 0x40058f3c;
 toascii = 0x4000c720;
-tolower = 0x40001868;
-toupper = 0x40001884;
 __utoa = 0x400561f0;
 utoa = 0x40056258;

components/esp_rom/esp32/ld/esp32.rom.newlib-reent-funcs.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2023-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2023-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -59,3 +59,16 @@ __sinit_lock_release = 0x40001e2c;
 __env_lock = 0x40001fd4;
 __env_unlock = 0x40001fe0;
 _getenv_r = 0x40001fbc;
+tolower = 0x40001868;
+toupper = 0x40001884;
+isalnum = 0x40000f04;
+isalpha = 0x40000f18;
+isdigit = 0x40000f64;
+islower = 0x40000f78;
+isspace = 0x40000fd4;
+isupper = 0x40000fe8;
+strcasecmp = 0x400011cc;
+strcoll = 0x40001398;
+strlwr = 0x40001524;
+strncasecmp = 0x40001550;
+strupr = 0x4000174c;

components/esp_rom/esp32c2/ld/esp32c2.rom.libc.ld

@@ -9,41 +9,28 @@ strlen = 0x400004a8;
 strstr = 0x400004ac;
 bzero = 0x400004b0;
 sbrk = 0x400004b8;
-isalnum = 0x400004bc;
-isalpha = 0x400004c0;
 isascii = 0x400004c4;
 isblank = 0x400004c8;
 iscntrl = 0x400004cc;
-isdigit = 0x400004d0;
-islower = 0x400004d4;
 isgraph = 0x400004d8;
 isprint = 0x400004dc;
 ispunct = 0x400004e0;
-isspace = 0x400004e4;
-isupper = 0x400004e8;
-toupper = 0x400004ec;
-tolower = 0x400004f0;
 toascii = 0x400004f4;
 memccpy = 0x400004f8;
 memchr = 0x400004fc;
 memrchr = 0x40000500;
-strcasecmp = 0x40000504;
 strcasestr = 0x40000508;
 strcat = 0x4000050c;
 strchr = 0x40000514;
 strcspn = 0x40000518;
-strcoll = 0x4000051c;
 strlcat = 0x40000520;
 strlcpy = 0x40000524;
-strlwr = 0x40000528;
-strncasecmp = 0x4000052c;
 strncat = 0x40000530;
 strnlen = 0x40000538;
 strrchr = 0x4000053c;
 strsep = 0x40000540;
 strspn = 0x40000544;
 strtok_r = 0x40000548;
-strupr = 0x4000054c;
 longjmp = 0x40000550;
 setjmp = 0x40000554;
 abs = 0x40000558;

components/esp_rom/esp32c2/ld/esp32c2.rom.newlib.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -63,3 +63,16 @@ puts = 0x4000065c;
 putc = 0x40000660;
 putchar = 0x40000664;
 __errno = 0x40000670;
+toupper = 0x400004ec;
+tolower = 0x400004f0;
+isalnum = 0x400004bc;
+isalpha = 0x400004c0;
+isdigit = 0x400004d0;
+islower = 0x400004d4;
+isspace = 0x400004e4;
+isupper = 0x400004e8;
+strcasecmp = 0x40000504;
+strcoll = 0x4000051c;
+strlwr = 0x40000528;
+strncasecmp = 0x4000052c;
+strupr = 0x4000054c;

components/esp_rom/esp32c3/ld/esp32c3.rom.libc.ld

@@ -9,41 +9,28 @@ strlen = 0x40000374;
 strstr = 0x40000378;
 bzero = 0x4000037c;
 sbrk = 0x40000384;
-isalnum = 0x40000388;
-isalpha = 0x4000038c;
 isascii = 0x40000390;
 isblank = 0x40000394;
 iscntrl = 0x40000398;
-isdigit = 0x4000039c;
-islower = 0x400003a0;
 isgraph = 0x400003a4;
 isprint = 0x400003a8;
 ispunct = 0x400003ac;
-isspace = 0x400003b0;
-isupper = 0x400003b4;
-toupper = 0x400003b8;
-tolower = 0x400003bc;
 toascii = 0x400003c0;
 memccpy = 0x400003c4;
 memchr = 0x400003c8;
 memrchr = 0x400003cc;
-strcasecmp = 0x400003d0;
 strcasestr = 0x400003d4;
 strcat = 0x400003d8;
 strchr = 0x400003e0;
 strcspn = 0x400003e4;
-strcoll = 0x400003e8;
 strlcat = 0x400003ec;
 strlcpy = 0x400003f0;
-strlwr = 0x400003f4;
-strncasecmp = 0x400003f8;
 strncat = 0x400003fc;
 strnlen = 0x40000404;
 strrchr = 0x40000408;
 strsep = 0x4000040c;
 strspn = 0x40000410;
 strtok_r = 0x40000414;
-strupr = 0x40000418;
 longjmp = 0x4000041c;
 setjmp = 0x40000420;
 abs = 0x40000424;

components/esp_rom/esp32c3/ld/esp32c3.rom.newlib.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -35,3 +35,16 @@ PROVIDE( _fwalk = 0x40000464 );
 PROVIDE( _fwalk_reent = 0x40000468 );
 PROVIDE( __swbuf_r = 0x40000474 );
 __swbuf = 0x40000478;
+toupper = 0x400003b8;
+tolower = 0x400003bc;
+isalnum = 0x40000388;
+isalpha = 0x4000038c;
+isdigit = 0x4000039c;
+islower = 0x400003a0;
+isspace = 0x400003b0;
+isupper = 0x400003b4;
+strcasecmp = 0x400003d0;
+strcoll = 0x400003e8;
+strlwr = 0x400003f4;
+strncasecmp = 0x400003f8;
+strupr = 0x40000418;

components/esp_rom/esp32c5/ld/esp32c5.rom.libc.ld

@@ -24,41 +24,28 @@ strlen = 0x400004d8;
 strstr = 0x400004dc;
 bzero = 0x400004e0;
 sbrk = 0x400004e8;
-isalnum = 0x400004ec;
-isalpha = 0x400004f0;
 isascii = 0x400004f4;
 isblank = 0x400004f8;
 iscntrl = 0x400004fc;
-isdigit = 0x40000500;
-islower = 0x40000504;
 isgraph = 0x40000508;
 isprint = 0x4000050c;
 ispunct = 0x40000510;
-isspace = 0x40000514;
-isupper = 0x40000518;
-toupper = 0x4000051c;
-tolower = 0x40000520;
 toascii = 0x40000524;
 memccpy = 0x40000528;
 memchr = 0x4000052c;
 memrchr = 0x40000530;
-strcasecmp = 0x40000534;
 strcasestr = 0x40000538;
 strcat = 0x4000053c;
 strchr = 0x40000544;
 strcspn = 0x40000548;
-strcoll = 0x4000054c;
 strlcat = 0x40000550;
 strlcpy = 0x40000554;
-strlwr = 0x40000558;
-strncasecmp = 0x4000055c;
 strncat = 0x40000560;
 strnlen = 0x40000568;
 strrchr = 0x4000056c;
 strsep = 0x40000570;
 strspn = 0x40000574;
 strtok_r = 0x40000578;
-strupr = 0x4000057c;
 longjmp = 0x40000580;
 setjmp = 0x40000584;
 abs = 0x40000588;

components/esp_rom/esp32c5/ld/esp32c5.rom.newlib.ld

@@ -37,3 +37,16 @@ __swhatbuf_r = 0x400005d4;
 __swbuf_r = 0x400005d8;
 __swbuf = 0x400005dc;
 __swsetup_r = 0x400005e0;
+toupper = 0x4000051c;
+tolower = 0x40000520;
+isalnum = 0x400004ec;
+isalpha = 0x400004f0;
+isdigit = 0x40000500;
+islower = 0x40000504;
+isspace = 0x40000514;
+isupper = 0x40000518;
+strcasecmp = 0x40000534;
+strcoll = 0x4000054c;
+strlwr = 0x40000558;
+strncasecmp = 0x4000055c;
+strupr = 0x4000057c;

components/esp_rom/esp32c6/ld/esp32c6.rom.libc.ld

@@ -9,41 +9,28 @@ strlen = 0x400004c8;
 strstr = 0x400004cc;
 bzero = 0x400004d0;
 sbrk = 0x400004d8;
-isalnum = 0x400004dc;
-isalpha = 0x400004e0;
 isascii = 0x400004e4;
 isblank = 0x400004e8;
 iscntrl = 0x400004ec;
-isdigit = 0x400004f0;
-islower = 0x400004f4;
 isgraph = 0x400004f8;
 isprint = 0x400004fc;
 ispunct = 0x40000500;
-isspace = 0x40000504;
-isupper = 0x40000508;
-toupper = 0x4000050c;
-tolower = 0x40000510;
 toascii = 0x40000514;
 memccpy = 0x40000518;
 memchr = 0x4000051c;
 memrchr = 0x40000520;
-strcasecmp = 0x40000524;
 strcasestr = 0x40000528;
 strcat = 0x4000052c;
 strchr = 0x40000534;
 strcspn = 0x40000538;
-strcoll = 0x4000053c;
 strlcat = 0x40000540;
 strlcpy = 0x40000544;
-strlwr = 0x40000548;
-strncasecmp = 0x4000054c;
 strncat = 0x40000550;
 strnlen = 0x40000558;
 strrchr = 0x4000055c;
 strsep = 0x40000560;
 strspn = 0x40000564;
 strtok_r = 0x40000568;
-strupr = 0x4000056c;
 longjmp = 0x40000570;
 setjmp = 0x40000574;
 abs = 0x40000578;

components/esp_rom/esp32c6/ld/esp32c6.rom.newlib.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -39,3 +39,16 @@ __swhatbuf_r = 0x400005c4;
 __swbuf_r = 0x400005c8;
 __swbuf = 0x400005cc;
 __swsetup_r = 0x400005d0;
+toupper = 0x4000050c;
+tolower = 0x40000510;
+isalnum = 0x400004dc;
+isalpha = 0x400004e0;
+isdigit = 0x400004f0;
+islower = 0x400004f4;
+isspace = 0x40000504;
+isupper = 0x40000508;
+strcasecmp = 0x40000524;
+strcoll = 0x4000053c;
+strlwr = 0x40000548;
+strncasecmp = 0x4000054c;
+strupr = 0x4000056c;

components/esp_rom/esp32c61/ld/esp32c61.rom.libc.ld

@@ -9,41 +9,28 @@ strlen = 0x400004d8;
 strstr = 0x400004dc;
 bzero = 0x400004e0;
 sbrk = 0x400004e8;
-isalnum = 0x400004ec;
-isalpha = 0x400004f0;
 isascii = 0x400004f4;
 isblank = 0x400004f8;
 iscntrl = 0x400004fc;
-isdigit = 0x40000500;
-islower = 0x40000504;
 isgraph = 0x40000508;
 isprint = 0x4000050c;
 ispunct = 0x40000510;
-isspace = 0x40000514;
-isupper = 0x40000518;
-toupper = 0x4000051c;
-tolower = 0x40000520;
 toascii = 0x40000524;
 memccpy = 0x40000528;
 memchr = 0x4000052c;
 memrchr = 0x40000530;
-strcasecmp = 0x40000534;
 strcasestr = 0x40000538;
 strcat = 0x4000053c;
 strchr = 0x40000544;
 strcspn = 0x40000548;
-strcoll = 0x4000054c;
 strlcat = 0x40000550;
 strlcpy = 0x40000554;
-strlwr = 0x40000558;
-strncasecmp = 0x4000055c;
 strncat = 0x40000560;
 strnlen = 0x40000568;
 strrchr = 0x4000056c;
 strsep = 0x40000570;
 strspn = 0x40000574;
 strtok_r = 0x40000578;
-strupr = 0x4000057c;
 longjmp = 0x40000580;
 setjmp = 0x40000584;
 abs = 0x40000588;

components/esp_rom/esp32c61/ld/esp32c61.rom.newlib.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -39,3 +39,16 @@ __swhatbuf_r = 0x400005d4;
 __swbuf_r = 0x400005d8;
 __swbuf = 0x400005dc;
 __swsetup_r = 0x400005e0;
+toupper = 0x4000051c;
+tolower = 0x40000520;
+isalnum = 0x400004ec;
+isalpha = 0x400004f0;
+isdigit = 0x40000500;
+islower = 0x40000504;
+isspace = 0x40000514;
+isupper = 0x40000518;
+strcasecmp = 0x40000534;
+strcoll = 0x4000054c;
+strlwr = 0x40000558;
+strncasecmp = 0x4000055c;
+strupr = 0x4000057c;

components/esp_rom/esp32h2/ld/esp32h2.rom.libc.ld

@@ -9,41 +9,28 @@ strlen = 0x400004c0;
 strstr = 0x400004c4;
 bzero = 0x400004c8;
 sbrk = 0x400004d0;
-isalnum = 0x400004d4;
-isalpha = 0x400004d8;
 isascii = 0x400004dc;
 isblank = 0x400004e0;
 iscntrl = 0x400004e4;
-isdigit = 0x400004e8;
-islower = 0x400004ec;
 isgraph = 0x400004f0;
 isprint = 0x400004f4;
 ispunct = 0x400004f8;
-isspace = 0x400004fc;
-isupper = 0x40000500;
-toupper = 0x40000504;
-tolower = 0x40000508;
 toascii = 0x4000050c;
 memccpy = 0x40000510;
 memchr = 0x40000514;
 memrchr = 0x40000518;
-strcasecmp = 0x4000051c;
 strcasestr = 0x40000520;
 strcat = 0x40000524;
 strchr = 0x4000052c;
 strcspn = 0x40000530;
-strcoll = 0x40000534;
 strlcat = 0x40000538;
 strlcpy = 0x4000053c;
-strlwr = 0x40000540;
-strncasecmp = 0x40000544;
 strncat = 0x40000548;
 strnlen = 0x40000550;
 strrchr = 0x40000554;
 strsep = 0x40000558;
 strspn = 0x4000055c;
 strtok_r = 0x40000560;
-strupr = 0x40000564;
 longjmp = 0x40000568;
 setjmp = 0x4000056c;
 abs = 0x40000570;

components/esp_rom/esp32h2/ld/esp32h2.rom.newlib.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -39,3 +39,16 @@ __swhatbuf_r = 0x400005bc;
 __swbuf_r = 0x400005c0;
 __swbuf = 0x400005c4;
 __swsetup_r = 0x400005c8;
+toupper = 0x40000504;
+tolower = 0x40000508;
+isalnum = 0x400004d4;
+isalpha = 0x400004d8;
+isdigit = 0x400004e8;
+islower = 0x400004ec;
+isspace = 0x400004fc;
+isupper = 0x40000500;
+strcasecmp = 0x4000051c;
+strcoll = 0x40000534;
+strlwr = 0x40000540;
+strncasecmp = 0x40000544;
+strupr = 0x40000564;

components/esp_rom/esp32h21/ld/esp32h21.rom.libc.ld

@@ -9,41 +9,28 @@ strlen = 0x400004b8;
 strstr = 0x400004bc;
 bzero = 0x400004c0;
 sbrk = 0x400004c8;
-isalnum = 0x400004cc;
-isalpha = 0x400004d0;
 isascii = 0x400004d4;
 isblank = 0x400004d8;
 iscntrl = 0x400004dc;
-isdigit = 0x400004e0;
-islower = 0x400004e4;
 isgraph = 0x400004e8;
 isprint = 0x400004ec;
 ispunct = 0x400004f0;
-isspace = 0x400004f4;
-isupper = 0x400004f8;
-toupper = 0x400004fc;
-tolower = 0x40000500;
 toascii = 0x40000504;
 memccpy = 0x40000508;
 memchr = 0x4000050c;
 memrchr = 0x40000510;
-strcasecmp = 0x40000514;
 strcasestr = 0x40000518;
 strcat = 0x4000051c;
 strchr = 0x40000524;
 strcspn = 0x40000528;
-strcoll = 0x4000052c;
 strlcat = 0x40000530;
 strlcpy = 0x40000534;
-strlwr = 0x40000538;
-strncasecmp = 0x4000053c;
 strncat = 0x40000540;
 strnlen = 0x40000548;
 strrchr = 0x4000054c;
 strsep = 0x40000550;
 strspn = 0x40000554;
 strtok_r = 0x40000558;
-strupr = 0x4000055c;
 longjmp = 0x40000560;
 setjmp = 0x40000564;
 abs = 0x40000568;

components/esp_rom/esp32h21/ld/esp32h21.rom.newlib.ld

@@ -39,3 +39,16 @@ __swhatbuf_r = 0x400005b4;
 __swbuf_r = 0x400005b8;
 __swbuf = 0x400005bc;
 __swsetup_r = 0x400005c0;
+toupper = 0x400004fc;
+tolower = 0x40000500;
+isalnum = 0x400004cc;
+isalpha = 0x400004d0;
+isdigit = 0x400004e0;
+islower = 0x400004e4;
+isspace = 0x400004f4;
+isupper = 0x400004f8;
+strcasecmp = 0x40000514;
+strcoll = 0x4000052c;
+strlwr = 0x40000538;
+strncasecmp = 0x4000053c;
+strupr = 0x4000055c;

components/esp_rom/esp32h4/ld/esp32h4.rom.libc.ld

@@ -31,41 +31,28 @@ strlen = 0x400004b8;
 strstr = 0x400004bc;
 bzero = 0x400004c0;
 sbrk = 0x400004c4;
-isalnum = 0x400004c8;
-isalpha = 0x400004cc;
 isascii = 0x400004d0;
 isblank = 0x400004d4;
 iscntrl = 0x400004d8;
-isdigit = 0x400004dc;
-islower = 0x400004e0;
 isgraph = 0x400004e4;
 isprint = 0x400004e8;
 ispunct = 0x400004ec;
-isspace = 0x400004f0;
-isupper = 0x400004f4;
-toupper = 0x400004f8;
-tolower = 0x400004fc;
 toascii = 0x40000500;
 memccpy = 0x40000504;
 memchr = 0x40000508;
 memrchr = 0x4000050c;
-strcasecmp = 0x40000510;
 strcasestr = 0x40000514;
 strcat = 0x40000518;
 strchr = 0x4000051c;
 strcspn = 0x40000520;
-strcoll = 0x40000524;
 strlcat = 0x40000528;
 strlcpy = 0x4000052c;
-strlwr = 0x40000530;
-strncasecmp = 0x40000534;
 strncat = 0x40000538;
 strnlen = 0x4000053c;
 strrchr = 0x40000540;
 strsep = 0x40000544;
 strspn = 0x40000548;
 strtok_r = 0x4000054c;
-strupr = 0x40000550;
 longjmp = 0x40000554;
 setjmp = 0x40000558;
 abs = 0x4000055c;

components/esp_rom/esp32h4/ld/esp32h4.rom.newlib.ld

@@ -37,3 +37,16 @@ __swhatbuf_r = 0x40000484;
 __swbuf_r = 0x40000488;
 __swbuf = 0x4000048c;
 __swsetup_r = 0x40000490;
+toupper = 0x400004f8;
+tolower = 0x400004fc;
+isalnum = 0x400004c8;
+isalpha = 0x400004cc;
+isdigit = 0x400004dc;
+islower = 0x400004e0;
+isspace = 0x400004f0;
+isupper = 0x400004f4;
+strcasecmp = 0x40000510;
+strcoll = 0x40000524;
+strlwr = 0x40000530;
+strncasecmp = 0x40000534;
+strupr = 0x40000550;

components/esp_rom/esp32p4/ld/esp32p4.rom.libc.ld

@@ -9,41 +9,28 @@ strlen = 0x4fc00288;
 strstr = 0x4fc0028c;
 bzero = 0x4fc00290;
 sbrk = 0x4fc00298;
-isalnum = 0x4fc0029c;
-isalpha = 0x4fc002a0;
 isascii = 0x4fc002a4;
 isblank = 0x4fc002a8;
 iscntrl = 0x4fc002ac;
-isdigit = 0x4fc002b0;
-islower = 0x4fc002b4;
 isgraph = 0x4fc002b8;
 isprint = 0x4fc002bc;
 ispunct = 0x4fc002c0;
-isspace = 0x4fc002c4;
-isupper = 0x4fc002c8;
-toupper = 0x4fc002cc;
-tolower = 0x4fc002d0;
 toascii = 0x4fc002d4;
 memccpy = 0x4fc002d8;
 memchr = 0x4fc002dc;
 memrchr = 0x4fc002e0;
-strcasecmp = 0x4fc002e4;
 strcasestr = 0x4fc002e8;
 strcat = 0x4fc002ec;
 strchr = 0x4fc002f4;
 strcspn = 0x4fc002f8;
-strcoll = 0x4fc002fc;
 strlcat = 0x4fc00300;
 strlcpy = 0x4fc00304;
-strlwr = 0x4fc00308;
-strncasecmp = 0x4fc0030c;
 strncat = 0x4fc00310;
 strnlen = 0x4fc00318;
 strrchr = 0x4fc0031c;
 strsep = 0x4fc00320;
 strspn = 0x4fc00324;
 strtok_r = 0x4fc00328;
-strupr = 0x4fc0032c;
 longjmp = 0x4fc00330;
 setjmp = 0x4fc00334;
 abs = 0x4fc00338;

components/esp_rom/esp32p4/ld/esp32p4.rom.newlib.ld

@@ -39,3 +39,16 @@ __swhatbuf_r = 0x4fc00384;
 __swbuf_r = 0x4fc00388;
 __swbuf = 0x4fc0038c;
 __swsetup_r = 0x4fc00390;
+toupper = 0x4fc002cc;
+tolower = 0x4fc002d0;
+isalnum = 0x4fc0029c;
+isalpha = 0x4fc002a0;
+isdigit = 0x4fc002b0;
+islower = 0x4fc002b4;
+isspace = 0x4fc002c4;
+isupper = 0x4fc002c8;
+strcasecmp = 0x4fc002e4;
+strcoll = 0x4fc002fc;
+strlwr = 0x4fc00308;
+strncasecmp = 0x4fc0030c;
+strupr = 0x4fc0032c;

components/esp_rom/esp32s2/ld/esp32s2.rom.libc-funcs.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -17,18 +17,12 @@ PROVIDE ( __assert = 0x4001a430 );
 PROVIDE ( __assert_func = 0x4001a408 );
 bzero = 0x400078c8;
 div = 0x40000620;
-isalnum = 0x400078d8;
-isalpha = 0x400078e8;
 isascii = 0x4001aaec;
 isblank = 0x400078f8;
 iscntrl = 0x40007918;
-isdigit = 0x40007930;
 isgraph = 0x40007968;
-islower = 0x40007948;
 isprint = 0x40007980;
 ispunct = 0x40007994;
-isspace = 0x400079ac;
-isupper = 0x400079c4;
 labs = 0x40000648;
 ldiv = 0x40000650;
 longjmp = 0x400005a4;
@@ -44,14 +38,11 @@ setjmp = 0x40000540;
 strcat = 0x4001ad90;
 strchr = 0x4001adb0;
 strcmp = 0x40007be4;
-strcoll = 0x40007ce8;
 strcpy = 0x40007cfc;
 strcspn = 0x4001adcc;
 strlcat = 0x40007db8;
 strlcpy = 0x4001adf8;
 strlen = 0x40007e08;
-strlwr = 0x40007e68;
-strncasecmp = 0x40007e94;
 strncat = 0x4001ae34;
 strncmp = 0x4001ae64;
 strncpy = 0x40007f20;
@@ -62,7 +53,4 @@ strspn = 0x4001aebc;
 strstr = 0x4001aee8;
 __strtok_r = 0x4001af18;
 strtok_r = 0x4001af7c;
-strupr = 0x40008084;
 toascii = 0x4001af90;
-tolower = 0x40008158;
-toupper = 0x40008174;

components/esp_rom/esp32s2/ld/esp32s2.rom.newlib-reent-funcs.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2023-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2023-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -50,3 +50,15 @@ __locale_ctype_ptr_l = 0x40001c24;
 __locale_mb_cur_max = 0x40001c0c;
 strcasecmp = 0x40007b38;
 strcasestr = 0x40007b7c;
+tolower = 0x40008158;
+toupper = 0x40008174;
+isalnum = 0x400078d8;
+isalpha = 0x400078e8;
+isdigit = 0x40007930;
+islower = 0x40007948;
+isspace = 0x400079ac;
+isupper = 0x400079c4;
+strcoll = 0x40007ce8;
+strlwr = 0x40007e68;
+strncasecmp = 0x40007e94;
+strupr = 0x40008084;

components/esp_rom/esp32s3/ld/esp32s3.rom.libc.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -16,41 +16,28 @@ strlen = 0x40001248;
 strstr = 0x40001254;
 bzero = 0x40001260;
 sbrk = 0x40001278;
-isalnum = 0x40001284;
-isalpha = 0x40001290;
 isascii = 0x4000129c;
 isblank = 0x400012a8;
 iscntrl = 0x400012b4;
-isdigit = 0x400012c0;
-islower = 0x400012cc;
 isgraph = 0x400012d8;
 isprint = 0x400012e4;
 ispunct = 0x400012f0;
-isspace = 0x400012fc;
-isupper = 0x40001308;
-toupper = 0x40001314;
-tolower = 0x40001320;
 toascii = 0x4000132c;
 memccpy = 0x40001338;
 memchr = 0x40001344;
 memrchr = 0x40001350;
-strcasecmp = 0x4000135c;
 strcasestr = 0x40001368;
 strcat = 0x40001374;
 strchr = 0x4000138c;
 strcspn = 0x40001398;
-strcoll = 0x400013a4;
 strlcat = 0x400013b0;
 strlcpy = 0x400013bc;
-strlwr = 0x400013c8;
-strncasecmp = 0x400013d4;
 strncat = 0x400013e0;
 strnlen = 0x400013f8;
 strrchr = 0x40001404;
 strsep = 0x40001410;
 strspn = 0x4000141c;
 strtok_r = 0x40001428;
-strupr = 0x40001434;
 longjmp = 0x40001440;
 setjmp = 0x4000144c;
 abs = 0x40001458;

components/esp_rom/esp32s3/ld/esp32s3.rom.newlib.ld

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -29,3 +29,16 @@ PROVIDE( _fwalk = 0x40001518 );
 PROVIDE( _fwalk_reent = 0x40001524 );
 PROVIDE( __swbuf_r = 0x40001548 );
 __swbuf = 0x40001554;
+toupper = 0x40001314;
+tolower = 0x40001320;
+isalnum = 0x40001284;
+isalpha = 0x40001290;
+isdigit = 0x400012c0;
+islower = 0x400012cc;
+isspace = 0x400012fc;
+isupper = 0x40001308;
+strcasecmp = 0x4000135c;
+strcoll = 0x400013a4;
+strlwr = 0x400013c8;
+strncasecmp = 0x400013d4;
+strupr = 0x40001434;

components/esp_system/ld/elf_misc.ld.in

@@ -69,7 +69,9 @@
     * And so forth...
     */
    *(.rela.*)
+#if CONFIG_LIBC_NEWLIB
    *(.got .got.plt) /* TODO: GCC-382 */
+#endif
 #if !EH_FRAME_LINKING_ENABLED
    *(.eh_frame_hdr)
    *(.eh_frame)

components/esp_system/ld/esp32/sections.ld.in

@@ -360,12 +360,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .ctors.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .ctors))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -388,12 +390,24 @@ SECTIONS
 
     /* TLS data. */
     ALIGNED_SYMBOL(4, _thread_local_start)
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata)
     *(.tdata.*)
     *(.tbss)
     *(.tbss.*)
     _thread_local_end = ABSOLUTE(.);
   } > default_rodata_seg
+  ASSERT_PICOLIBC_REENT_STUB()
 
   _flash_rodata_align = ALIGNOF(.flash.rodata);
 

components/esp_system/ld/esp32c2/sections.ld.in

@@ -188,6 +188,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -199,12 +202,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -254,24 +259,42 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
-
-    . = ALIGN(ALIGNOF(.flash.tbss));
     _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
 
-  .flash.tbss (NOLOAD) :
+    /* tbss sections */
-  {
     _thread_local_bss_start = ABSOLUTE(.);
-
     *(.tbss .tbss.* .gnu.linkonce.tb.*)
     *(.tcommon .tcommon.*)
-
     _thread_local_bss_end = ABSOLUTE(.);
+
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -284,7 +307,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32c3/sections.ld.in

@@ -310,6 +310,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -321,12 +324,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -376,24 +381,42 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
-
-    . = ALIGN(ALIGNOF(.flash.tbss));
     _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
 
-  .flash.tbss (NOLOAD) :
+    /* tbss sections */
-  {
     _thread_local_bss_start = ABSOLUTE(.);
-
     *(.tbss .tbss.* .gnu.linkonce.tb.*)
     *(.tcommon .tcommon.*)
-
     _thread_local_bss_end = ABSOLUTE(.);
+
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -406,7 +429,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32c5/sections.ld.in

@@ -359,6 +359,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -370,12 +373,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -425,32 +430,48 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
+    _thread_local_data_end = ABSOLUTE(.);
 
-    . = ALIGN(ALIGNOF(.flash.tbss));
+    /* tbss sections */
+    _thread_local_bss_start = ABSOLUTE(.);
+    *(.tbss .tbss.* .gnu.linkonce.tb.*)
+    *(.tcommon .tcommon.*)
+    _thread_local_bss_end = ABSOLUTE(.);
 
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
 #if CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
     /* Align the end of flash rodata region as per PMP granularity to allow using the
      * page alignment gap created while mapping the flash region into the PSRAM memory.
      */
     . = ALIGN(_esp_pmp_align_size);
 #endif // CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
-
-    _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
-
-  .flash.tbss (NOLOAD) :
-  {
-    _thread_local_bss_start = ABSOLUTE(.);
-
-    *(.tbss .tbss.* .gnu.linkonce.tb.*)
-    *(.tcommon .tcommon.*)
-
-    _thread_local_bss_end = ABSOLUTE(.);
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -463,7 +484,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32c6/sections.ld.in

@@ -355,6 +355,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -366,12 +369,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -421,24 +426,42 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
-
-    . = ALIGN(ALIGNOF(.flash.tbss));
     _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
 
-  .flash.tbss (NOLOAD) :
+    /* tbss sections */
-  {
     _thread_local_bss_start = ABSOLUTE(.);
-
     *(.tbss .tbss.* .gnu.linkonce.tb.*)
     *(.tcommon .tcommon.*)
-
     _thread_local_bss_end = ABSOLUTE(.);
+
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -451,7 +474,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32c61/sections.ld.in

@@ -217,6 +217,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -228,6 +231,7 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
 
@@ -235,6 +239,7 @@ SECTIONS
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -284,32 +289,48 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
+    _thread_local_data_end = ABSOLUTE(.);
 
-    . = ALIGN(ALIGNOF(.flash.tbss));
+    /* tbss sections */
+    _thread_local_bss_start = ABSOLUTE(.);
+    *(.tbss .tbss.* .gnu.linkonce.tb.*)
+    *(.tcommon .tcommon.*)
+    _thread_local_bss_end = ABSOLUTE(.);
 
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
 #if CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
     /* Align the end of flash rodata region as per PMP granularity to allow using the
      * page alignment gap created while mapping the flash region into the PSRAM memory.
      */
     . = ALIGN(_esp_pmp_align_size);
 #endif // CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
-
-    _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
-
-  .flash.tbss (NOLOAD) :
-  {
-    _thread_local_bss_start = ABSOLUTE(.);
-
-    *(.tbss .tbss.* .gnu.linkonce.tb.*)
-    *(.tcommon .tcommon.*)
-
-    _thread_local_bss_end = ABSOLUTE(.);
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -322,7 +343,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32h2/sections.ld.in

@@ -357,6 +357,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -368,12 +371,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -423,24 +428,42 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
-
-    . = ALIGN(ALIGNOF(.flash.tbss));
     _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
 
-  .flash.tbss (NOLOAD) :
+    /* tbss sections */
-  {
     _thread_local_bss_start = ABSOLUTE(.);
-
     *(.tbss .tbss.* .gnu.linkonce.tb.*)
     *(.tcommon .tcommon.*)
-
     _thread_local_bss_end = ABSOLUTE(.);
+
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -453,7 +476,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32h21/sections.ld.in

@@ -346,6 +346,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -357,12 +360,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -412,24 +417,42 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
-
-    . = ALIGN(ALIGNOF(.flash.tbss));
     _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
 
-  .flash.tbss (NOLOAD) :
+    /* tbss sections */
-  {
     _thread_local_bss_start = ABSOLUTE(.);
-
     *(.tbss .tbss.* .gnu.linkonce.tb.*)
     *(.tcommon .tcommon.*)
-
     _thread_local_bss_end = ABSOLUTE(.);
+
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -442,7 +465,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32h4/sections.ld.in

@@ -191,6 +191,9 @@ SECTIONS
 
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -202,12 +205,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -257,24 +262,42 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
-
-    . = ALIGN(ALIGNOF(.flash.tbss));
     _thread_local_data_end = ABSOLUTE(.);
-  } > default_rodata_seg
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
 
-  .flash.tbss (NOLOAD) :
+    /* tbss sections */
-  {
     _thread_local_bss_start = ABSOLUTE(.);
-
     *(.tbss .tbss.* .gnu.linkonce.tb.*)
     *(.tcommon .tcommon.*)
-
     _thread_local_bss_end = ABSOLUTE(.);
+
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
   } > default_rodata_seg
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -287,7 +310,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     mapping[rodata_noload]
   } > default_rodata_seg

components/esp_system/ld/esp32p4/sections.ld.in

@@ -362,6 +362,9 @@ SECTIONS
     arrays[flash_rodata]
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -379,12 +382,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -434,32 +439,48 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
+    _thread_local_data_end = ABSOLUTE(.);
 
-    . = ALIGN(ALIGNOF(.flash.tbss));
+    /* tbss sections */
+    _thread_local_bss_start = ABSOLUTE(.);
+    *(.tbss .tbss.* .gnu.linkonce.tb.*)
+    *(.tcommon .tcommon.*)
+    _thread_local_bss_end = ABSOLUTE(.);
 
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
 #if CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
     /* Align the end of flash rodata region as per PMP granularity to allow using the
      * page alignment gap created while mapping the flash region into the PSRAM memory.
      */
     . = ALIGN(_esp_pmp_align_size);
 #endif // CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
-
-    _thread_local_data_end = ABSOLUTE(.);
-  } > rodata_seg_low
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
-
-  .flash.tbss (NOLOAD) :
-  {
-    _thread_local_bss_start = ABSOLUTE(.);
-
-    *(.tbss .tbss.* .gnu.linkonce.tb.*)
-    *(.tcommon .tcommon.*)
-
-    _thread_local_bss_end = ABSOLUTE(.);
   } > rodata_seg_low
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -472,7 +493,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     arrays[rodata_noload]
     mapping[rodata_noload]

components/esp_system/ld/esp32p4/sections.rev3.ld.in

@@ -388,6 +388,9 @@ SECTIONS
     arrays[flash_rodata]
     mapping[flash_rodata]
 
+#if CONFIG_LIBC_PICOLIBC
+    *(.got .got.plt) /* TODO: GCC-439 */
+#endif
     *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
     *(.gnu.linkonce.r.*)
     *(.rodata1)
@@ -405,12 +408,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -460,11 +465,37 @@ SECTIONS
 
   .flash.tdata :
   {
+    /* Keep tdata and tbss sections contiguous (no gaps between them).
+     * The TLS runtime code calculates offsets assuming these sections are
+     * adjacent. Gaps would cause incorrect address calculations, leading
+     * to accessing wrong memory.
+     *
+     * Storing all TLS structures in flash increases binary size, but avoids
+     * runtime issues and reduces TLS allocations on the stack.
+     */
+    /* tdata sections */
     _thread_local_data_start = ABSOLUTE(.);
-
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata .tdata.* .gnu.linkonce.td.*)
+    _thread_local_data_end = ABSOLUTE(.);
 
-    . = ALIGN(ALIGNOF(.flash.tbss));
+    /* tbss sections */
+    _thread_local_bss_start = ABSOLUTE(.);
+    *(.tbss .tbss.* .gnu.linkonce.tb.*)
+    *(.tcommon .tcommon.*)
+    _thread_local_bss_end = ABSOLUTE(.);
+
+    . = ALIGN(ALIGNOF(.flash.rodata_noload));
 
 #if CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
     /* Align the end of flash rodata region as per PMP granularity to allow using the
@@ -472,20 +503,11 @@ SECTIONS
      */
     . = ALIGN(_esp_pmp_align_size);
 #endif // CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
-
-    _thread_local_data_end = ABSOLUTE(.);
-  } > rodata_seg_low
-  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
-
-  .flash.tbss (NOLOAD) :
-  {
-    _thread_local_bss_start = ABSOLUTE(.);
-
-    *(.tbss .tbss.* .gnu.linkonce.tb.*)
-    *(.tcommon .tcommon.*)
-
-    _thread_local_bss_end = ABSOLUTE(.);
   } > rodata_seg_low
+  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.rodata_noload)
+  ASSERT(_thread_local_data_end == _thread_local_bss_start,
+         "tdata and tbss must be contiguous.")
+  ASSERT_PICOLIBC_REENT_STUB()
 
   /**
    * This section contains all the rodata that is not used
@@ -498,7 +520,7 @@ SECTIONS
      * driver to maintain the virtual address.
      * NOLOAD rodata may not be included in this section.
      */
-    _rodata_reserved_end = ADDR(.flash.tbss);
+    _rodata_reserved_end = .;
 
     arrays[rodata_noload]
     mapping[rodata_noload]

components/esp_system/ld/esp32s2/sections.ld.in

@@ -363,12 +363,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .ctors.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .ctors))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -391,12 +393,24 @@ SECTIONS
 
     /* TLS data. */
     ALIGNED_SYMBOL(4, _thread_local_start)
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata)
     *(.tdata.*)
     *(.tbss)
     *(.tbss.*)
     _thread_local_end = ABSOLUTE(.);
   } > default_rodata_seg
+  ASSERT_PICOLIBC_REENT_STUB()
 
   _flash_rodata_align = ALIGNOF(.flash.rodata);
 

components/esp_system/ld/esp32s3/sections.ld.in

@@ -374,12 +374,14 @@ SECTIONS
      * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
      */
     ALIGNED_SYMBOL(4, __preinit_array_start)
+    ALIGNED_SYMBOL(4, __bothinit_array_start)
     KEEP (*(.preinit_array))
     __preinit_array_end = ABSOLUTE(.);
     ALIGNED_SYMBOL(4, __init_array_start)
     KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .ctors.*)))
     KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .ctors))
     __init_array_end = ABSOLUTE(.);
+    __bothinit_array_end = ABSOLUTE(.);
 
     /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
     ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
@@ -402,12 +404,24 @@ SECTIONS
 
     /* TLS data. */
     ALIGNED_SYMBOL(4, _thread_local_start)
+#if CONFIG_LIBC_PICOLIBC
+    _picolibc_reent_stub_start = ABSOLUTE(.);
+    KEEP(*(.tdata.errno))
+#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    /* Reproduce the public fields from struct _reent. */
+    KEEP(*(.tdata.tls_stdin))
+    KEEP(*(.tdata.tls_stdout))
+    KEEP(*(.tdata.tls_stderr))
+#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+    _picolibc_reent_stub_end = ABSOLUTE(.);
+#endif // CONFIG_LIBC_PICOLIBC
     *(.tdata)
     *(.tdata.*)
     *(.tbss)
     *(.tbss.*)
     _thread_local_end = ABSOLUTE(.);
   } > default_rodata_seg
+  ASSERT_PICOLIBC_REENT_STUB()
 
   _flash_rodata_align = ALIGNOF(.flash.rodata);
 

components/esp_system/ld/ld.common

@@ -100,3 +100,14 @@ ASSERT((ADDR(NEXT_SECTION) == ADDR(PREV_SECTION) + SIZEOF(PREV_SECTION)), \
 #else
 #define SECTION_AFTER_FLASH_RODATA .flash.tdata
 #endif
+
+#if CONFIG_LIBC_PICOLIBC
+# if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
+#  define PICOLIBC_REENT_STUB 16
+# else
+#  define PICOLIBC_REENT_STUB 4
+# endif
+#define ASSERT_PICOLIBC_REENT_STUB() ASSERT((_picolibc_reent_stub_end - _picolibc_reent_stub_start) == PICOLIBC_REENT_STUB, "Newlib _reent stub have wrong size")
+#else
+#define ASSERT_PICOLIBC_REENT_STUB()
+#endif

components/esp_system/port/cpu_start.c

@@ -197,6 +197,21 @@ static void core_intr_matrix_clear(void)
 #endif // SOC_INT_CLIC_SUPPORTED
 }
 
+#if CONFIG_LIBC_PICOLIBC
+FORCE_INLINE_ATTR IRAM_ATTR void init_pre_rtos_tls_area(int cpu_num)
+{
+    /**
+     * Initialize the TLS area before RTOS starts, in case any code tries to access
+     * TLS variables.
+     *
+     * TODO IDF-14914: Currently, we only initialize errno, which is the first TLS
+     * variable as guaranteed by the linker script.
+     */
+    static int s_errno_array[SOC_CPU_CORES_NUM];
+    esp_cpu_set_threadptr(&s_errno_array[cpu_num]);
+}
+#endif
+
 #if !CONFIG_ESP_SYSTEM_SINGLE_CORE_MODE
 void startup_resume_other_cores(void)
 {
@@ -217,6 +232,10 @@ void ESP_SYSTEM_IRAM_ATTR call_start_cpu1(void)
     );
 #endif  //#ifdef __riscv
 
+#if CONFIG_LIBC_PICOLIBC
+    init_pre_rtos_tls_area(1);
+#endif
+
 #if SOC_BRANCH_PREDICTOR_SUPPORTED
     esp_cpu_branch_prediction_enable();
 #endif  //#if SOC_BRANCH_PREDICTOR_SUPPORTED
@@ -943,6 +962,10 @@ void IRAM_ATTR call_start_cpu0(void)
     // Clear BSS. Please do not attempt to do any complex stuff (like early logging) before this.
     init_bss(rst_reas);
 
+#if CONFIG_LIBC_PICOLIBC
+    init_pre_rtos_tls_area(0);
+#endif
+
     // When the APP is loaded into ram for execution, some hardware initialization steps used to be executed in the
     // bootloader are done here.
 #if CONFIG_APP_BUILD_TYPE_RAM

components/hal/platform_port/include/hal/assert.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -11,8 +11,20 @@
 extern "C" {
 #endif
 
-extern void __assert_func(const char *file, int line, const char *func, const char *expr);
+#if CONFIG_LIBC_PICOLIBC
-extern void abort(void);
+#if defined(__cplusplus) && __cplusplus >= 201103L
+#define __noreturn [[noreturn]]
+#elif __has_attribute(__noreturn__)
+#define __noreturn __attribute__((__noreturn__))
+#else
+#define __noreturn
+#endif
+#else
+#define __noreturn
+#endif
+
+__noreturn void __assert_func(const char *file, int line, const char *func, const char *expr);
+__noreturn void abort(void);
 
 #ifndef __ASSERT_FUNC
 #ifdef __ASSERT_FUNCTION

components/heap/test_apps/heap_tests/main/test_heap_trace.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  */
@@ -128,13 +128,21 @@ TEST_CASE("heap trace wrapped buffer check", "[heap-trace]")
     heap_trace_stop();
 }
 
-static void print_floats_task(void *ignore)
+static void trace_libc_allocs_task(void *ignore)
 {
     heap_trace_start(HEAP_TRACE_ALL);
+
+#if CONFIG_LIBC_NEWLIB
     char buf[16] = { };
     volatile float f = 12.3456;
     sprintf(buf, "%.4f", f);
     TEST_ASSERT_EQUAL_STRING("12.3456", buf);
+#endif
+#if CONFIG_LIBC_PICOLIBC
+    FILE* f = fdopen(100, "r");
+    fclose(f);
+#endif
+
     heap_trace_stop();
 
     vTaskDelete(NULL);
@@ -158,11 +166,10 @@ TEST_CASE("can trace allocations made by newlib", "[heap-trace]")
        - We also do the tracing in the task so we only capture things directly related to it.
     */
 
-    xTaskCreate(print_floats_task, "print_float", 4096, NULL, 5, NULL);
+    xTaskCreate(trace_libc_allocs_task, "trace_libc_allocs_task", 4096, NULL, 5, NULL);
     vTaskDelay(10);
 
-    /* has to be at least a few as newlib allocates via multiple different function calls */
+    TEST_ASSERT(heap_trace_get_count() > 0);
-    TEST_ASSERT(heap_trace_get_count() > 3);
 }
 
 TEST_CASE("can stop recording allocs but continue recording frees", "[heap-trace]")

components/lwip/port/esp32xx/include/arch/cc.h

@@ -3,7 +3,7 @@
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
- * SPDX-FileContributor: 2018-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileContributor: 2018-2025 Espressif Systems (Shanghai) CO LTD
  */
 #ifndef __ARCH_CC_H__
 #define __ARCH_CC_H__
@@ -25,10 +25,18 @@ extern "C" {
 #endif // BYTE_ORDER
 
 #define LWIP_DONT_PROVIDE_BYTEORDER_FUNCTIONS
+#ifndef htons
 #define htons(x) __builtin_bswap16(x)
+#endif
+#ifndef ntohs
 #define ntohs(x) __builtin_bswap16(x)
+#endif
+#ifndef htonl
 #define htonl(x) __builtin_bswap32(x)
+#endif
+#ifndef ntohl
 #define ntohl(x) __builtin_bswap32(x)
+#endif
 
 #ifndef CONFIG_LWIP_ESP_LWIP_ASSERT
 #define LWIP_NOASSERT 1

components/lwip/test_apps/main/lwip_test.c

@@ -5,6 +5,7 @@
  */
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 #include <esp_types.h>
 
 #include "freertos/FreeRTOS.h"

components/riscv/include/riscv/rv_utils.h

@@ -132,6 +132,18 @@ FORCE_INLINE_ATTR void __attribute__((always_inline)) rv_utils_set_cycle_count(u
 #endif
 }
 
+FORCE_INLINE_ATTR void rv_utils_set_threadptr(void *ptr)
+{
+    asm volatile("mv tp, %0" :: "r"(ptr));
+}
+
+FORCE_INLINE_ATTR void *rv_utils_get_threadptr(void)
+{
+    void *thread_ptr;
+    asm volatile("mv %0, tp" : "=r"(thread_ptr));
+    return thread_ptr;
+}
+
 /* ------------------------------------------------- CPU Interrupts ----------------------------------------------------
  *
  * ------------------------------------------------------------------------------------------------------------------ */

components/sdmmc/include/sd_protocol_defs.h

@@ -25,6 +25,7 @@
 
 #include <stdint.h>
 #include <limits.h>
+#include <stddef.h>
 
 #ifdef __cplusplus
 extern "C" {

components/soc/esp32p4/register/hw_ver3/soc/pmu_struct.h

@@ -7,6 +7,7 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <stddef.h>
 #include "pmu_reg.h"
 #ifdef __cplusplus
 extern "C" {

components/soc/project_include.cmake

@@ -80,30 +80,8 @@ if(CONFIG_IDF_TOOLCHAIN_GCC)
         if(NOT CONFIG_SOC_CPU_MISALIGNED_ACCESS_ON_PMP_MISMATCH_ISSUE)
             idf_toolchain_add_flags(COMPILE_OPTIONS "-mtune=esp-base")
         endif()
+        idf_toolchain_rerun_abi_detection()
     else()
         message(FATAL_ERROR "Unknown Espressif architecture: ${CONFIG_IDF_TARGET_ARCH}")
     endif()
-
-    # Workaround: Re-run CMake compiler ABI detection after ABI flags are set.
-    #
-    # Problem: CMake performs compiler checks at an early stage during
-    # toolchain.cmake processing. At this early stage, response files are not yet
-    # ready, which causes CMake paths (e.g., CMAKE_<lang>_IMPLICIT_LINK_DIRECTORIES)
-    # to be incorrectly determined.
-    #
-    # Solution: Re-run the ABI detection after ABI flags are present to correctly
-    # determine these paths.
-    #
-    # Note: If the CMake API changes, this solution may need to be revised.
-    set(lang_ext_pairs "C|c" "CXX|cpp")
-    include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerABI.cmake)
-    foreach(lang_ext ${lang_ext_pairs})
-        string(REPLACE "|" ";" lang_ext_parts ${lang_ext})
-        list(GET lang_ext_parts 0 lang)
-        list(GET lang_ext_parts 1 ext)
-        if(DEFINED CMAKE_${lang}_ABI_COMPILED)
-            unset(CMAKE_${lang}_ABI_COMPILED)
-            cmake_determine_compiler_abi(${lang} ${CMAKE_ROOT}/Modules/CMake${lang}CompilerABI.${ext})
-        endif()
-    endforeach()
 endif()

components/tcp_transport/transport_ssl.c

@@ -8,6 +8,7 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <unistd.h>
+#include <sys/select.h>
 
 #include "esp_tls.h"
 #include "esp_log.h"

components/ulp/esp32ulp_mapgen.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python
-# SPDX-FileCopyrightText: 2016-2024 Espressif Systems (Shanghai) CO LTD
+# SPDX-FileCopyrightText: 2016-2025 Espressif Systems (Shanghai) CO LTD
 # SPDX-License-Identifier: Apache-2.0
 #
 # esp32ulp_mapgen utility converts a symbol list provided by nm into an export script
@@ -16,50 +16,61 @@ UTIL = os.path.basename(__file__)
 def name_mangling(name: str) -> str:
     # Simple and dumb name mangling for namespaced name following GCC algorithm
     ns, n = name.split('::')
-    return '_ZN{0}{1}{2}{3}E'.format(len(ns), ns, len(n), n)
+    return f'_ZN{len(ns)}{ns}{len(n)}{n}E'
 
 
-def gen_ld_h_from_sym(f_sym: typing.TextIO, f_ld: typing.TextIO, f_h: typing.TextIO, base_addr: int, prefix: str) -> None:
+def gen_ld_h_from_sym(
-    f_ld.write(textwrap.dedent(
+    f_sym: typing.TextIO, f_ld: typing.TextIO, f_h: typing.TextIO, base_addr: int, prefix: str
+) -> None:
+    f_ld.write(
+        textwrap.dedent(
             f"""
         /* ULP variable definitions for the linker.
          * This file is generated automatically by {UTIL} utility.
          */
         """  # noqa: E222
-    ))
+        )
+    )
     cpp_mode = False
     var_prefix = prefix
     namespace = ''
     if '::' in prefix:
         # C++ mode, let's avoid the extern "C" type and instead use namespace
-        f_h.write(textwrap.dedent(
+        f_h.write(
+            textwrap.dedent(
                 f"""
             /* ULP variable definitions for the compiler.
              * This file is generated automatically by {UTIL} utility.
              */
             #pragma once
             """  # noqa: E222
-        ))
+            )
+        )
         tmp = prefix.split('::')
         namespace = tmp[0]
         var_prefix = '_'.join(tmp[1:])  # Limit to a single namespace here to avoid complex mangling rules
         f_h.write(f'namespace {namespace} {{\n')
         cpp_mode = True
     else:
-        f_h.write(textwrap.dedent(
+        f_h.write(
+            textwrap.dedent(
                 f"""
             /* ULP variable definitions for the compiler.
              * This file is generated automatically by {UTIL} utility.
              */
             #pragma once
+            #include <stdint.h>
             #ifdef __cplusplus
             extern "C" {{
             #endif\n
             """  # noqa: E222
-        ))
+            )
+        )
 
     # Format the regular expression to match the readelf output
-    expr = re.compile(r'^.*(?P<address>[a-f0-9]{8})\s+(?P<size>\d+) (OBJECT|NOTYPE)\s+GLOBAL\s+DEFAULT\s+[^ ]+ (?P<name>.*)$')
+    expr = re.compile(
+        r'^.*(?P<address>[a-f0-9]{8})\s+(?P<size>\d+) (OBJECT|NOTYPE)\s+GLOBAL\s+DEFAULT\s+[^ ]+ (?P<name>.*)$'
+    )
     for line in f_sym:
         # readelf format output has the following structure:
         #   Num:    Value  Size Type    Bind   Vis      Ndx Name
@@ -90,23 +101,31 @@ def gen_ld_h_from_sym(f_sym: typing.TextIO, f_ld: typing.TextIO, f_h: typing.Tex
     if cpp_mode:
         f_h.write('}\n')
     else:
-        f_h.write(textwrap.dedent(
+        f_h.write(
+            textwrap.dedent(
                 """
             #ifdef __cplusplus
             }
             #endif
             """
-        ))
+            )
+        )
 
 
 def main() -> None:
-    description = ('This application generates .h and .ld files for symbols defined in input file. '
+    description = (
+        'This application generates .h and .ld files for symbols defined in input file. '
         'The input symbols file can be generated using readelf utility like this: '
-                   '<PREFIX>readelf -sW <elf_file> > <symbols_file>')
+        '<PREFIX>readelf -sW <elf_file> > <symbols_file>'
+    )
 
     parser = argparse.ArgumentParser(description=description)
-    parser.add_argument('-s', '--symfile', required=True, help='symbols file name', metavar='SYMFILE', type=argparse.FileType('r'))
+    parser.add_argument(
-    parser.add_argument('-o', '--outputfile', required=True, help='destination .h and .ld files name prefix', metavar='OUTFILE')
+        '-s', '--symfile', required=True, help='symbols file name', metavar='SYMFILE', type=argparse.FileType('r')
+    )
+    parser.add_argument(
+        '-o', '--outputfile', required=True, help='destination .h and .ld files name prefix', metavar='OUTFILE'
+    )
     parser.add_argument('--base-addr', required=True, help='base address of the ULP memory, to be added to each symbol')
     parser.add_argument('-p', '--prefix', required=False, help='prefix for generated header file', default='ulp_')
 

components/vfs/test_apps/main/test_vfs_fd.c

@@ -7,6 +7,7 @@
 #include "sdkconfig.h"
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 #include <unistd.h>
 #include <errno.h>
 #include <sys/fcntl.h>

components/vfs/test_apps/main/test_vfs_lwip.c

@@ -8,6 +8,7 @@
 #include <sys/fcntl.h>
 #include <sys/param.h>
 #include <sys/socket.h>
+#include <sys/stat.h>
 #include "unity.h"
 #include "test_utils.h"
 

components/vfs/test_apps/main/test_vfs_select.c

@@ -8,6 +8,7 @@
 #include <unistd.h>
 #include <sys/fcntl.h>
 #include <sys/param.h>
+#include <sys/select.h>
 #include "unity.h"
 #include "freertos/FreeRTOS.h"
 #include "driver/uart.h"

components/xtensa/include/xt_utils.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2020-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2020-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -82,6 +82,18 @@ FORCE_INLINE_ATTR void xt_utils_wait_for_intr(void)
     asm volatile ("waiti 0\n");
 }
 
+FORCE_INLINE_ATTR void xt_utils_set_threadptr(void *ptr)
+{
+    asm volatile ("wur.threadptr %0" :: "r"(ptr));
+}
+
+FORCE_INLINE_ATTR void *xt_utils_get_threadptr(void)
+{
+    void *thread_ptr;
+    asm volatile ("rur.threadptr %0" : "=r"(thread_ptr));
+    return thread_ptr;
+}
+
 /* ------------------------------------------------- CPU Interrupts ----------------------------------------------------
  *
  * ------------------------------------------------------------------------------------------------------------------ */

docs/en/api-guides/stdio.rst

@@ -58,13 +58,26 @@ Enabling one of these option will cause the corresponding VFS driver to be built
 Standard Streams and FreeRTOS Tasks
 -----------------------------------
 
+ESP-IDF provides two different implementations of standard I/O streams based on the selected LibC implementation defined by :ref:`CONFIG_LIBC`. The behavior of ``stdin``, ``stdout``, and ``stderr`` streams differs between these implementations, particularly regarding how they are shared across FreeRTOS tasks.
+
+Common to both implementations, each stream (``stdin``, ``stdout``, ``stderr``) has a mutex associated with it to protect the stream from concurrent access by multiple tasks. For example, if two tasks are writing to ``stdout`` at the same time, the mutex ensures that the outputs from each task are not mixed together.
+
+Newlib
+^^^^^^
+
 In ESP-IDF, to save RAM, ``FILE`` objects for ``stdin``, ``stdout``, and ``stderr`` are shared between all FreeRTOS tasks, but the pointers to these objects are unique for every task. This means that:
 
 - It is possible to change ``stdin``, ``stdout``, and ``stderr`` for any given task without affecting other tasks, e.g., by doing ``stdin = fopen("/dev/uart/1", "r")``.
 - To change the default ``stdin``, ``stdout``, ``stderr`` streams for new tasks, modify ``_GLOBAL_REENT->_stdin`` (``_stdout``, ``_stderr``) before creating the task.
 - Closing default ``stdin``, ``stdout``, or ``stderr`` using ``fclose`` closes the ``FILE`` stream object, which will affect all other tasks.
 
-Each stream (``stdin``, ``stdout``, ``stderr``) has a mutex associated with it. This mutex is used to protect the stream from concurrent access by multiple tasks. For example, if two tasks are writing to ``stdout`` at the same time, the mutex will ensure that the outputs from each task are not mixed together.
+Picolibc
+^^^^^^^^
+
+According to the POSIX standard, all default ``stdin``, ``stdout``, and ``stderr`` streams are global and shared between all FreeRTOS tasks. This means that:
+
+- Modifying ``stdin``, ``stdout``, or ``stderr`` will affect all other tasks. It is not possible to change standard I/O streams for specific tasks.
+- If a thread-local stream is needed, it should be implemented in the application code by opening a file stream and using it within tasks, e.g., ``fscanf()``, ``fprintf()``, etc.
 
 Blocking and non-blocking I/O
 -----------------------------

docs/en/migration-guides/release-6.x/6.0/system.rst

@@ -3,6 +3,71 @@ System
 
 :link_to_translation:`zh_CN:[中文]`
 
+Default LibC changed from Newlib to PicolibC
+--------------------------------------------
+
+Since ESP-IDF v6.0, the default LibC used in builds has switched to the PicolibC implementation.
+
+.. note::
+   PicolibC is a Newlib fork with a rewritten stdio implementation whose goal is to consume less memory.
+
+In most cases, no application behavior changes are expected, except for reduced binary size and less stack consumption on I/O operations.
+
+.. warning::
+   **Breaking change:** It is not possible to redefine stdin, stdout, and stderr for specific tasks as was possible with Newlib. These streams are global and shared between all tasks. This is POSIX-standardized behavior.
+
+:ref:`CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY`, which is enabled by default, provides limited compatibility with Newlib by providing thread-local copies of global stdin, stdout, stderr, and the getreent() implementation. If a library built with Newlib headers operates with "internal" fields of "struct reent", there may be task stack corruption. Note that manipulating "struct reent" fields is expected only by the Newlib library itself.
+
+If you are not linking against external libraries built against Newlib headers, you may disable :ref:`CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY` to save a small amount of memory.
+
+Newlib is still maintained in ESP-IDF toolchains. To switch to using it, select Newlib in menuconfig via the option LIBC_NEWLIB in :ref:`CONFIG_LIBC`.
+
+Comparison of Newlib vs Picolibc
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+There are a small example that shows the motivation of switching to Picolibc:
+
+.. code-block:: c
+
+    FILE *f = fopen("/dev/console", "w");
+    for (int i = 0; i < 10; i++)
+    {
+        fprintf(f, "hello world %s\n", "🤖");
+        fprintf(f, "%.1000f\n", 3.141592653589793);
+        fprintf(f, "%1000d\n", 42);
+    }
+
+The test code was compiled with both Newlib and Picolibc, and the results were compared on ESP32-C3:
+
+.. list-table:: Comparison of Newlib vs Picolibc
+   :header-rows: 1
+   :widths: 30 20 20 20
+   :stub-columns: 1
+
+   * - Metric
+     - Newlib
+     - Picolibc
+     - Difference
+   * - Binary size (bytes)
+     - 280,128
+     - 224,656
+     - 19.80%
+   * - Stack usage (bytes)
+     - 1,748
+     - 802
+     - 54.12%
+   * - Heap usage (bytes)
+     - 1,652
+     - 376
+     - 77.24%
+   * - Performance (CPU cycles)
+     - 278,232,026
+     - 279,823,800
+     - 0.59%
+
+.. note::
+   Even when :ref:`CONFIG_LIBC_NEWLIB_NANO_FORMAT` is enabled, which disables float formatting, applications with Picolibc are still smaller by 6% (224,592 vs 239,888 bytes).
+
 Xtensa
 ------
 

examples/network/simple_sniffer/main/cmd_sniffer.c

@@ -7,6 +7,7 @@
 */
 #include <string.h>
 #include <stdlib.h>
+#include <sys/time.h>
 #include "argtable3/argtable3.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"

examples/openthread/ot_sleepy_device/deep_sleep/main/esp_ot_sleepy_device.c

@@ -16,6 +16,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <string.h>
+#include <sys/time.h>
 #include "esp_err.h"
 #include "esp_event.h"
 #include "esp_log.h"

examples/storage/fatfs/fatfsgen/main/fatfsgen_example_main.c

@@ -7,6 +7,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 #include "esp_vfs.h"
 #include "esp_vfs_fat.h"
 #include "esp_err.h"

tools/cmake/toolchain_flags.cmake

@@ -155,3 +155,28 @@ endfunction()
 function(idf_toolchain_remove_flags)
     _process_toolchain_flag_options()
 endfunction()
+
+# Workaround: Re-run CMake compiler ABI detection after ABI flags are set.
+#
+# Problem: CMake performs compiler checks at an early stage during
+# toolchain.cmake processing. At this early stage, response files are not yet
+# ready, which causes CMake paths (e.g., CMAKE_<lang>_IMPLICIT_LINK_DIRECTORIES)
+# to be incorrectly determined.
+#
+# Solution: Re-run the ABI detection after ABI flags are present to correctly
+# determine these paths.
+#
+# Note: If the CMake API changes, this solution may need to be revised.
+macro(idf_toolchain_rerun_abi_detection)
+    set(lang_ext_pairs "C|c" "CXX|cpp")
+    include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerABI.cmake)
+    foreach(lang_ext ${lang_ext_pairs})
+        string(REPLACE "|" ";" lang_ext_parts ${lang_ext})
+        list(GET lang_ext_parts 0 lang)
+        list(GET lang_ext_parts 1 ext)
+        if(DEFINED CMAKE_${lang}_ABI_COMPILED)
+            unset(CMAKE_${lang}_ABI_COMPILED)
+            cmake_determine_compiler_abi(${lang} ${CMAKE_ROOT}/Modules/CMake${lang}CompilerABI.${ext})
+        endif()
+    endforeach()
+endmacro()

tools/test_apps/storage/fatfsgen/main/fatfsgen_example_main.c

@@ -7,6 +7,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 #include "esp_vfs.h"
 #include "esp_vfs_fat.h"
 #include "sdkconfig.h"

tools/test_apps/system/init_array/main/test_app_main.c

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  */
 #include <stdio.h>
+#include <stdint.h>
 
 __attribute__((constructor))
 void foo(void)

tools/test_apps/system/panic/pytest_panic.py

@@ -1159,6 +1159,7 @@ def spiram_xip_irom_alignment_reg_execute_violation(dut: PanicTestDut, test_func
 
 
 @pytest.mark.generic
+@pytest.mark.temp_skip_ci(targets=['esp32c5'], reason='TODO IDF-14835')
 @idf_parametrize('config, target', CONFIGS_MEMPROT_SPIRAM_XIP_IROM_ALIGNMENT_HEAP, indirect=['config', 'target'])
 def test_spiram_xip_irom_alignment_reg_execute_violation(dut: PanicTestDut, test_func_name: str) -> None:
     spiram_xip_irom_alignment_reg_execute_violation(dut, test_func_name)
@@ -1187,6 +1188,7 @@ def spiram_xip_drom_alignment_reg_execute_violation(dut: PanicTestDut, test_func
 
 
 @pytest.mark.generic
+@pytest.mark.temp_skip_ci(targets=['esp32c5'], reason='TODO IDF-14835')
 @idf_parametrize('config, target', CONFIGS_MEMPROT_SPIRAM_XIP_DROM_ALIGNMENT_HEAP, indirect=['config', 'target'])
 def test_spiram_xip_drom_alignment_reg_execute_violation(dut: PanicTestDut, test_func_name: str) -> None:
     spiram_xip_drom_alignment_reg_execute_violation(dut, test_func_name)