kbuild: Add -Wa,--fatal-warnings to as-instr invocation

Certain assembler instruction tests may only induce warnings from the assembler on an unsupported instruction or option, which causes as-instr to succeed when it was expected to fail. Some tests workaround this limitation by additionally testing that invalid input fails as expected. However, this is fragile if the assembler is changed to accept the invalid input, as it will cause the instruction/option to be unavailable like it was unsupported even when it is. Use '-Wa,--fatal-warnings' in the as-instr macro to turn these warnings into hard errors, which avoids this fragility and makes tests more robust and well formed. Cc: [email protected] Suggested-by: Eric Biggers <[email protected]> Signed-off-by: Nathan Chancellor <[email protected]> Tested-by: Eric Biggers <[email protected]> Tested-by: Andy Chiu <[email protected]> Reviewed-by: Andy Chiu <[email protected]> Tested-by: Conor Dooley <[email protected]> Reviewed-by: Conor Dooley <[email protected]> Acked-by: Masahiro Yamada <[email protected]> Link: https://lore.kernel.org/r/20240125-fix-riscv-option-arch-llvm-18-v1-1-390ac9cc3cd0@kernel.org Signed-off-by: Palmer Dabbelt <[email protected]>
wafgo · Feb 17, 2024 · 0ee695a · 0ee695a
1 parent 6613476
commit 0ee695a
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diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
@@ -33,7 +33,7 @@ ld-option = $(success,$(LD) -v $(1))
 
 # $(as-instr,<instr>)
 # Return y if the assembler supports <instr>, n otherwise
-as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler-with-cpp -o /dev/null -)
+as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o /dev/null -)
 
 # check if $(CC) and $(LD) exist
 $(error-if,$(failure,command -v $(CC)),C compiler '$(CC)' not found)

diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
@@ -38,7 +38,7 @@ as-option = $(call try-run,\
 # Usage: aflags-y += $(call as-instr,instr,option1,option2)
 
 as-instr = $(call try-run,\
-	printf "%b\n" "$(1)" | $(CC) -Werror $(CLANG_FLAGS) $(KBUILD_AFLAGS) -c -x assembler-with-cpp -o "$$TMP" -,$(2),$(3))
+	printf "%b\n" "$(1)" | $(CC) -Werror $(CLANG_FLAGS) $(KBUILD_AFLAGS) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o "$$TMP" -,$(2),$(3))
 
 # __cc-option
 # Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586)