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| author | Masahiro Yamada <masahiroy@kernel.org> | 2020-06-14 17:43:41 +0300 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2020-06-17 04:38:42 +0300 |
| commit | 4d0831e8a029c03f49f434f28b8faef9f0bd403f (patch) | |
| tree | e092627794e9b75423b84dbf66b0221f862b6340 /scripts | |
| parent | f2f02ebd8f3833626642688b2d2c6a7b3c141fa9 (diff) | |
| download | linux-4d0831e8a029c03f49f434f28b8faef9f0bd403f.tar.xz | |
kconfig: unify cc-option and as-option
cc-option and as-option are almost the same; both pass the flag to
$(CC). The main difference is the cc-option stops before the assemble
stage (-S option) whereas as-option stops after (-c option).
I chose -S because it is slightly faster, but $(cc-option,-gz=zlib)
returns a wrong result (https://lkml.org/lkml/2020/6/9/1529).
It has been fixed by commit 7b16994437c7 ("Makefile: Improve compressed
debug info support detection"), but the assembler should always be
invoked for more reliable compiler option tests.
However, you cannot simply replace -S with -c because the following
code in lib/Kconfig.debug would break:
depends on $(cc-option,-gsplit-dwarf)
The combination of -c and -gsplit-dwarf does not accept /dev/null as
output.
$ cat /dev/null | gcc -gsplit-dwarf -S -x c - -o /dev/null
$ echo $?
0
$ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o /dev/null
objcopy: Warning: '/dev/null' is not an ordinary file
$ echo $?
1
$ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o tmp.o
$ echo $?
0
There is another flag that creates an separate file based on the
object file path:
$ cat /dev/null | gcc -ftest-coverage -c -x c - -o /dev/null
<stdin>:1: error: cannot open /dev/null.gcno
So, we cannot use /dev/null to sink the output.
Align the cc-option implementation with scripts/Kbuild.include.
With -c option used in cc-option, as-option is unneeded.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'scripts')
| -rw-r--r-- | scripts/Kconfig.include | 8 |
1 files changed, 1 insertions, 7 deletions
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index c264da2b9b30..a5fe72c504ff 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -25,18 +25,12 @@ failure = $(if-success,$(1),n,y) # $(cc-option,<flag>) # Return y if the compiler supports <flag>, n otherwise -cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -S -x c /dev/null -o /dev/null) +cc-option = $(success,mkdir .tmp_$$$$; trap "rm -rf .tmp_$$$$" EXIT; $(CC) -Werror $(CLANG_FLAGS) $(1) -c -x c /dev/null -o .tmp_$$$$/tmp.o) # $(ld-option,<flag>) # Return y if the linker supports <flag>, n otherwise ld-option = $(success,$(LD) -v $(1)) -# $(as-option,<flag>) -# /dev/zero is used as output instead of /dev/null as some assembler cribs when -# both input and output are same. Also both of them have same write behaviour so -# can be easily substituted. -as-option = $(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero) - # $(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 -o /dev/null -) |