[PATCH 4/4] scripts/Kconfig.toolchain: Document minimum supported versions for dynamic checks

[Nathan Chancellor <nathan@kernel.org>]

To make it easier to clean up unnecessary dynamic checks when the
minimum supported version of a toolchain component is updated, add
comments documenting when features were first supported. Request that
future additions document this as well.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 scripts/Kconfig.toolchain | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/scripts/Kconfig.toolchain b/scripts/Kconfig.toolchain
index 26a62b15e9ab..3a9eb8317d59 100644
--- a/scripts/Kconfig.toolchain
+++ b/scripts/Kconfig.toolchain
@@ -1,4 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0-only
+# When adding a new dynamic check (such as {cc,ld}-option{,-str} or testing a
+# small program), please add a comment documenting the first version of the
+# tool that supported the feature being tested. For cc-option{,-str}, note the
+# "beware" comment below.
+
 config CC_VERSION_TEXT
 	string
 	default "$(CC_VERSION_TEXT)"
@@ -118,6 +123,7 @@ config GCC_ASM_GOTO_OUTPUT_BROKEN
 config CC_HAS_ASM_GOTO_OUTPUT
 	def_bool y
 	depends on !GCC_ASM_GOTO_OUTPUT_BROKEN
+	# supported since clang-10 and gcc-11
 	depends on $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
 
 config CC_HAS_ASM_GOTO_TIED_OUTPUT
@@ -129,6 +135,7 @@ config TOOLS_SUPPORT_RELR
 	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
 
 config CC_HAS_ASM_INLINE
+	# supported since clang-11 and gcc-9
 	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
 
 config CC_HAS_ASSUME
@@ -161,6 +168,8 @@ config CC_HAS_ASSUME
 #    pitfall.
 
 config CC_OPT_ZERO_INIT_PADDING_BITS
+	# supported since gcc-15. not needed for clang, as it does this by default since clang-20
+	# https://github.com/llvm/llvm-project/commit/7a086e1b2dc05f54afae3591614feede727601fa
 	def_string "$(cc-option-str,-fzero-init-padding-bits=all)"
 
 config CC_OPT_NO_ADDRSIG
@@ -168,12 +177,15 @@ config CC_OPT_NO_ADDRSIG
 	def_string "-fno-addrsig" if CC_IS_CLANG
 
 config CC_OPT_DIAGNOSTICS_SHOW_CONTEXT
+	# supported since gcc-16, not supported by clang
 	def_string "$(cc-option-str,-fdiagnostics-show-context=2)"
 
 config CC_OPT_DIAGNOSTICS_SHOW_INLINING_CHAIN
+	# supported since clang-23. not needed for gcc, as it does this by default
 	def_string "$(cc-option-str,-fdiagnostics-show-inlining-chain)"
 
 config CC_OPT_STRICT_FLEX_ARRAYS
+	# supported since clang-16 and gcc-13
 	def_string "$(cc-option-str,-fstrict-flex-arrays=3)"
 
 config CC_OPT_NO_ALLOW_STORE_DATA_RACES
@@ -181,51 +193,67 @@ config CC_OPT_NO_ALLOW_STORE_DATA_RACES
 	def_string "$(cc-option-str,-fno-allow-store-data-races,--param=allow-store-data-races=0)" if CC_IS_GCC
 
 config CC_HAS_MNOP_MCOUNT
+	# supported since clang-10 and gcc-9 but option is architecture specific
 	def_bool $(cc-option,-mnop-mcount)
 
 config LD_OPT_FORCE_GROUP_ALLOCATION
+	# supported since ld.lld 19 and GNU ld 2.29
 	def_string "$(ld-option-str,--force-group-allocation)"
 
 config LD_OPT_NO_WARN_RWX_SEGMENTS
+	# supported since GNU ld 2.39, not supported by ld.lld
 	def_string "$(ld-option-str,--no-warn-rwx-segments)"
 
 config CC_OPT_WNO_ADDRESS_OF_PACKED_MEMBER
+	# supported since clang-4 and gcc-9
 	def_string "$(cc-option-str,-Wno-address-of-packed-member)"
 
 config CC_OPT_WNO_FORMAT_OVERFLOW_NON_KPRINTF
+	# supported since clang-18, not needed for gcc
 	def_string "$(cc-option-str,-Wno-format-overflow-non-kprintf)"
 
 config CC_OPT_WNO_FORMAT_TRUNCATION_NON_KPRINTF
+	# supported since clang-18, not needed for gcc
 	def_string "$(cc-option-str,-Wno-format-truncation-non-kprintf)"
 
 config CC_OPT_WNO_DEFAULT_CONST_INIT_UNSAFE
+	# supported since clang-21, not needed for gcc
 	def_string "$(cc-option-str,-Wno-default-const-init-unsafe)"
 
 config CC_OPT_WNO_DANGLING_POINTER
+	# supported since gcc-12, not needed for clang
 	def_string "$(cc-option-str,-Wno-dangling-pointer)"
 
 config CC_OPT_WVLA_LARGER_THAN
+	# supported since gcc-7, not supported by clang
 	def_string "$(cc-option-str,-Wvla-larger-than=1)"
 
 config CC_HAS_WSTRINGOP_OVERFLOW
+	# supported since gcc-7, not supported by clang
 	def_bool $(cc-option,-Wstringop-overflow)
 
 config CC_OPT_WNO_UNTERMINATED_STRING_INITIALIZATION
+	# supported since gcc-15 and clang-21
 	def_string "$(cc-option-str,-Wno-unterminated-string-initialization)"
 
 config CC_OPT_WERROR_DESIGNATED_INIT
+	# supported since gcc-5, not supported by clang
 	def_string "$(cc-option-str,-Werror=designated-init)"
 
 config CC_OPT_WENUM_CONVERSION
+	# supported since clang-3.2 and gcc-10
 	def_string "$(cc-option-str,-Wenum-conversion)"
 
 config CC_OPT_WNO_PACKED_NOT_ALIGNED
+	# supported since gcc-8, not supported by clang
 	def_string "$(cc-option-str,-Wno-packed-not-aligned)"
 
 config CC_OPT_WNO_FORMAT_OVERFLOW
+	# supported since gcc-7 and clang-18
 	def_string "$(cc-option-str,-Wno-format-overflow)"
 
 config CC_OPT_WNO_STRINGOP_TRUNCATION
+	# supported since gcc-8, not supported by clang
 	def_string "$(cc-option-str,-Wno-stringop-truncation)"
 
 config CC_HAS_COUNTED_BY
@@ -252,14 +280,18 @@ config CC_HAS_BROKEN_COUNTED_BY_REF
 	default y if CC_IS_CLANG && CLANG_VERSION < 220100
 
 config CC_HAS_ALLOC_TOKEN
+	# supported since clang-22, not supported by gcc
 	def_bool $(cc-option,-falloc-token-max=123)
 
 config CC_HAS_MULTIDIMENSIONAL_NONSTRING
+	# supported since gcc-15 and clang-21
 	def_bool $(success,echo 'char tag[][4] __attribute__((__nonstring__)) = { };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror)
 
 config CC_OPT_INLINE_MEMSET
 	string
+	# supported since gcc-14
 	default "-finline-stringops=memset" if $(cc-option,-finline-stringops=memset)
+	# supported since clang-22
 	default "-mllvm -max-store-memset=4294967294" if $(cc-option,-mllvm -max-store-memset=4294967294)
 
 config LD_CAN_USE_KEEP_IN_OVERLAY

-- 
2.56.0