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From: Paolo Bonzini <pbonzini@redhat.com>
To: Bill Wendling <morbo@google.com>, kvm@vger.kernel.org
Cc: jmattson@google.com
Subject: Re: [kvm-unit-tests PATCH] Makefile: do not use "libgcc" for clang
Date: Wed, 5 May 2021 14:31:37 +0200	[thread overview]
Message-ID: <6b886420-91bf-0607-a51d-36fb090c8507@redhat.com> (raw)
In-Reply-To: <20210309045250.3333311-1-morbo@google.com>

On 09/03/21 05:52, Bill Wendling wrote:
> The -nostdlib flag disables the driver from adding libclang_rt.*.a
> during linking. Adding a specific library to the command line then
> causes the linker to report unresolved symbols, because the libraries
> that resolve those symbols aren't automatically added. Turns out clang
> doesn't need to specify that library.

This breaks 32-bit build with clang due to __udivdi3/__umoddi3.  Let me 
post an alternative.

Paolo

> Signed-off-by: Bill Wendling <morbo@google.com>
> ---
>   Makefile            | 6 ++++++
>   arm/Makefile.common | 2 ++
>   x86/Makefile.common | 2 ++
>   3 files changed, 10 insertions(+)
> 
> diff --git a/Makefile b/Makefile
> index e0828fe..61a1276 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -22,10 +22,16 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/
>   cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
>                 > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
>   
> +# cc-name
> +# Expands to either gcc or clang
> +cc-name = $(shell $(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc)
> +
>   #make sure env CFLAGS variable is not used
>   CFLAGS =
>   
> +ifneq ($(cc-name),clang)
>   libgcc := $(shell $(CC) --print-libgcc-file-name)
> +endif
>   
>   libcflat := lib/libcflat.a
>   cflatobjs := \
> diff --git a/arm/Makefile.common b/arm/Makefile.common
> index a123e85..94922aa 100644
> --- a/arm/Makefile.common
> +++ b/arm/Makefile.common
> @@ -58,7 +58,9 @@ OBJDIRS += lib/arm
>   libeabi = lib/arm/libeabi.a
>   eabiobjs = lib/arm/eabi_compat.o
>   
> +ifneq ($(cc-name),clang)
>   libgcc := $(shell $(CC) $(machine) --print-libgcc-file-name)
> +endif
>   
>   FLATLIBS = $(libcflat) $(LIBFDT_archive) $(libgcc) $(libeabi)
>   %.elf: LDFLAGS = -nostdlib $(arch_LDFLAGS)
> diff --git a/x86/Makefile.common b/x86/Makefile.common
> index 55f7f28..a96b236 100644
> --- a/x86/Makefile.common
> +++ b/x86/Makefile.common
> @@ -37,7 +37,9 @@ COMMON_CFLAGS += -O1
>   # stack.o relies on frame pointers.
>   KEEP_FRAME_POINTER := y
>   
> +ifneq ($(cc-name),clang)
>   libgcc := $(shell $(CC) -m$(bits) --print-libgcc-file-name)
> +endif
>   
>   # We want to keep intermediate file: %.elf and %.o
>   .PRECIOUS: %.elf %.o
> 


      parent reply	other threads:[~2021-05-05 12:31 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-09  4:52 Bill Wendling
2021-04-27 21:15 ` Bill Wendling
2021-05-04 17:07 ` Jim Mattson
2021-05-05 12:31 ` Paolo Bonzini [this message]

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