[klibc] [PATCH v2 1/5] Kbuild: add support for clang builds
ben at decadent.org.uk
Sat Mar 28 08:35:36 PDT 2020
On Fri, 2020-03-27 at 15:29 -0700, Bill Wendling wrote:
> From: Michael Davidson <md at google.com>
> Add cc-name to klibc/scripts/Kbuild.include.
> --- a/scripts/Kbuild.klibc
> +++ b/scripts/Kbuild.klibc
> @@ -107,8 +107,15 @@ KLIBCOBJCOPY := $(OBJCOPY)
> KLIBCOBJDUMP := $(OBJDUMP)
> # klibc include paths
> -KLIBCCPPFLAGS := -nostdinc -iwithprefix include \
> - -I$(KLIBCINC)/arch/$(KLIBCARCHDIR) \
> +ifeq ($(cc-name),clang)
> +# clang can't find the compiler-specific header <stdarg.h> if -nostdinc
> +# is specified so we have to omit it along with the -iwithprefix option.
> +# See b/35394554.
This seems to be an internal bug number. It doesn't belong here.
> +KLIBCCPPFLAGS :=
> +KLIBCCPPFLAGS := -nostdinc -iwithprefix include
It might make more sense to include these options only if cc-name is
"gcc". (Doesn't make any difference now, but if we ever add a third
compiler then it seems like it ought to work without this.)
> +KLIBCCPPFLAGS += -I$(KLIBCINC)/arch/$(KLIBCARCHDIR) \
> -I$(KLIBCINC)/bits$(KLIBCBITSIZE) \
> -I$(KLIBCOBJ)/../include \
> @@ -128,7 +135,13 @@ KLIBCCFLAGS += $(KLIBCCPPFLAGS) $(KLIBCREQFLAGS) $(KLIBCARCHREQFLAGS) \
> KLIBCAFLAGS += -D__ASSEMBLY__ -Wa,--noexecstack $(KLIBCCFLAGS)
> KLIBCSTRIPFLAGS += --strip-all -R .comment -R .note
> +# KLIBCLIBGCC_DEF appears to be unnecessary since klibc never uses -nostdlib
> +# when linking binaries, which means that any compiler specific libraries
> +# should be available automatically, no need to speciy an explicit path.
> +# Don't attempt to set it if we are using clang.
> +ifneq ($(cc-name),clang)
> KLIBCLIBGCC_DEF := $(shell $(KLIBCCC) $(KLIBCCFLAGS) --print-libgcc)
Seems like this should also check that cc-name is "gcc", then.
> KLIBCLIBGCC ?= $(KLIBCLIBGCC_DEF)
> KLIBCCRT0 := $(KLIBCOBJ)/arch/$(KLIBCARCHDIR)/crt0.o
> KLIBCLIBC := $(KLIBCOBJ)/libc.a
> diff --git a/usr/klibc/arch/x86_64/MCONFIG b/usr/klibc/arch/x86_64/MCONFIG
> index c5f2fa265a26..77e2ad279884 100644
> --- a/usr/klibc/arch/x86_64/MCONFIG
> +++ b/usr/klibc/arch/x86_64/MCONFIG
> @@ -15,13 +15,19 @@
> # debugging using gdb.
> KLIBCARCHREQFLAGS = -m64
> -KLIBCOPTFLAGS += -Os -fomit-frame-pointer -mno-sse \
> - -falign-functions=1 -falign-jumps=1 -falign-loops=1
> +KLIBCOPTFLAGS += -Os -fomit-frame-pointer -mno-sse
> ifeq ($(DEBUG),y)
> KLIBCOPTFLAGS += -g
> KLIBCOPTFLAGS += -fno-asynchronous-unwind-tables
> +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
Same here. It would be more readable to write:
KLIBCOPTFLAGS += gcc-specific-optimisations
KLIBCOPTFLAGS += clang-specific-optimisations
And this shouldn't need a comment.
> KLIBCBITSIZE = 64
> KLIBCLDFLAGS = -m elf_x86_64
This sentence contradicts itself - no actually it doesn't.
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