Re: [PATCH v3 02/17] tools build: Integrate libdebuginfod into test-all fast path

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The use of `$$(shell ...)` with unescaped variables like `$(CC)` inside a block evaluated by `$(eval)` causes a double-expansion bug that corrupts compiler flags containing `$`.
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commit 8e0d941d5a7133e71fe2afde9b8f70d691de8879
Author: Ian Rogers <irogers@google.com>
    
tools build: Integrate libdebuginfod into test-all fast path

This commit integrates libdebuginfod into the test-all fast path. It also
updates feature_check_code to short-circuit the feature check and avoid
a sub-make fork if a feature was already pre-detected.

> diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
> index 2f192d3bf61b9..064c75dd9914b 100644
> --- a/tools/build/Makefile.feature
> +++ b/tools/build/Makefile.feature
> @@ -8,7 +8,9 @@ endif
>  
>  feature_check = $(eval $(feature_check_code))
>  define feature_check_code
> -  feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CC="$(CC)" CXX="$(CXX)" CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0)
> +  ifeq ($(feature-$(1)),)
> +    feature-$(1) := $$(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CC="$(CC)" CXX="$(CXX)" CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0)

Does leaving variables like $(CC), $(EXTRA_CFLAGS), and $(LDFLAGS) unescaped
inside the $$(shell ...) block cause a double-expansion issue?

When eval parses the assignment, these variables are expanded in the first
pass, embedding their literal values into the string.

During the second pass, when the shell function is evaluated, Make scans the
embedded string again. If any compiler or linker flags contain a literal $
(such as -Wl,-rpath=$$ORIGIN), they will be incorrectly expanded during this
second pass (for example, replacing $O with the value of the output directory
variable O), corrupting the flags.

> +  endif
>  endef

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Sashiko AI review · https://sashiko.dev/#/patchset/20260514163409.927816-1-irogers@google.com?part=2