[klibc] [PATCH v2 3/5] Kbuild: use "libc.a" with clang

[Ben Hutchings]

On Fri, 2020-03-27 at 15:29 -0700, Bill Wendling wrote:
> Clang doesn't have a suitable replacement for libgcc readily available.
> Supply one that we know exists. Use "-fno-builtin-bcmp" to prevent clang
> from calling a function that doesn't exist.

Doesn't this contradict the comment added for KLIBCLIBGCC_DEF?

> Signed-off-by: Bill Wendling <morbo at google.com>
> ---
>  scripts/Kbuild.klibc          | 2 ++
>  usr/klibc/arch/x86_64/MCONFIG | 2 ++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/scripts/Kbuild.klibc b/scripts/Kbuild.klibc
> index 411d7ea9bea6..ba3f389626b3 100644
> --- a/scripts/Kbuild.klibc
> +++ b/scripts/Kbuild.klibc
> @@ -141,6 +141,8 @@ KLIBCSTRIPFLAGS  += --strip-all -R .comment -R .note
>  # Don't attempt to set it if we are using clang.
>  ifneq ($(cc-name),clang)
>  KLIBCLIBGCC_DEF  := $(shell $(KLIBCCC) $(KLIBCCFLAGS) --print-libgcc)
> +else
> +KLIBCLIBGCC_DEF  := $(KLIBCOBJ)/libc.a
>  endif
>  KLIBCLIBGCC	 ?= $(KLIBCLIBGCC_DEF)
>  KLIBCCRT0        := $(KLIBCOBJ)/arch/$(KLIBCARCHDIR)/crt0.o
> diff --git a/usr/klibc/arch/x86_64/MCONFIG b/usr/klibc/arch/x86_64/MCONFIG
> index ac1ac074c00a..a6ba7c85c68b 100644
> --- a/usr/klibc/arch/x86_64/MCONFIG
> +++ b/usr/klibc/arch/x86_64/MCONFIG
> @@ -26,6 +26,8 @@ ifneq ($(cc-name),clang)
>  # These options are not supported by clang but only result in a warning
>  # so we can't use a cc-option test to filter them.
>  KLIBCOPTFLAGS     += -falign-functions=1 -falign-jumps=1 -falign-loops=1
> +else
> +KLIBCOPTFLAGS     += -fno-builtin-bcmp

This doesn't seem to be an optimisation option.  It belongs in
KLIBCARCHREQFLAGS if it's really arch-specific.  But it appears to be
arch-independent, in which case scripts/Kbuild.klibc should add it to
KLIBCREQFLAGS.

Ben.

>  endif
>  
>  KLIBCBITSIZE      = 64
-- 
Ben Hutchings
This sentence contradicts itself - no actually it doesn't.

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