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Frantisek Hrbata
e1f43e15b7
After running objdump on all libraries, extract section names from the
stored raw output using regex and compute a fingerprint (MD5 hash of
section names + mtimes of fragment files, sdkconfig, and kconfig).
If the fingerprint matches the cached value from the previous run,
skip the expensive pyparsing + generation step entirely and touch
the output file to update its timestamp. The fingerprint file is
stored next to the output (e.g. sections.ld.fingerprint) in the build
directory.
This avoids the pyparsing bottleneck for the common case of editing
function bodies without adding or removing symbols — section names
in the object files are unchanged, so the generated sections.ld
would be identical. When sections do change, the full generation
runs and the fingerprint is updated.
Print "Skipping linker script generation, section names unchanged"
on the fingerprint hit path so build logs show when the optimization
fired. This makes it easy to diagnose user reports of unexpected
ldgen behavior — the build log directly shows whether the cache was
used.
Add an LDGEN_NO_CACHE environment variable to disable the cache as a
workaround in case the optimization causes problems. When set, ldgen
prints "Linker script generation caches disabled by LDGEN_NO_CACHE"
and runs full generation as before, leaving any existing fingerprint
file untouched.
Measured on wifi_station (205 libs, 67 .lf files), median of 10 runs:
before after
rebuild, section names unchanged 5.82s 0.82s
Closes https://github.com/espressif/esp-idf/issues/18408
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>