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Frantisek Hrbata
ac3217a9e4
The idf_component_optional_requires compatibility function in cmakev2
currently attempts to mimic the behavior of cmakev1 by adding a
dependency only if a component is already included in the build. In
cmakev1, this is handled by checking the BUILD_COMPONENTS list, which is
created during an early evaluation phase. Because cmakev2 removed this
early phase to allow for configuration-based component dependencies, the
build system does not inherently know which components will be part of
the build beforehand. To compensate, the current compatibility function
relies on the TARGET_EXISTS generator expression to determine if a
component should be linked.
This approach poses a problem because generator expressions are not
evaluated until the generation phase, but cmakev2 processes linker
scripts during the configuration phase by recursively scanning targets
linked to a library. Because the scanner does not recognize and cannot
evaluate generator expressions, any component linked optionally through
generator expression is skipped. If that component carries a linker
script, the script is never added to the library interface, resulting in
build failures. Since cmakev2 aims to support multiple libraries, a
component might also exist globally, causing TARGET_EXISTS to evaluate
to true, yet still be missed during a specific library's recursive scan,
leading to the same omission of necessary linker scripts.
To resolve this, the implementation of idf_component_optional_requires
is changed to check if a component is known to the build system in
COMPONENTS_DISCOVERED build property. If so, it is explicitly included
and linked directly via its interface target. While this may pull more
components into a build than the previous generator expression method,
potentially increasing build times, it ensures that dependency trees are
fully visible to the library target scanner. This serves as a practical
middle ground that maintains compatibility with existing components and
ensures build stability. This approach allows for the gradual fixing of
idf_component_optional_requires usage in components for cmakev2, with
the eventual goal of removing its usage in cmakev2 entirely.
This change also fixes cases where idf_component_optional_requires is
used to conditionally add requirements based on configuration options.
In cmakev2, the presence of a configuration option does not guarantee[1]
that a component has been included via add_subdirectory, unlike the
behavior in cmakev1. With this change even constructions like
```cmake
if(CONFIG_VFS_SUPPORT_IO)
idf_component_optional_requires(PRIVATE vfs)
endif()
```
will now work in cmakev2, as the updated idf_component_optional_requires
explicitly includes the required component if it is available to the
build system.
Closes https://github.com/espressif/esp-idf/issues/18133
[1] https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/build-system-v2.html#id9
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>
Documentation Source Folder
This folder contains source files of ESP-IDF documentation available in English and 中文.
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Use actual documentation generated within about 20 minutes on each commit:
Hosted Documentation
- English: https://docs.espressif.com/projects/esp-idf/en/latest/
- 中文: https://docs.espressif.com/projects/esp-idf/zh_CN/latest/
After you click any link to ESP-IDF Programming Guide, go to the top of the sidebar, then make sure you have the correct Espressif chip (target) and ESP-IDF version selected in the dropdown menus. You can also find a link on the bottom right to download the PDF version.
Building Documentation
The documentation is built using the python package esp-docs, which can be installed by running:
pip install esp-docs
For a summary of available options, run:
build-docs --help
For more information see the esp-docs documentation at https://github.com/espressif/esp-docs/blob/master/README.md