llvm dev - May 2018 - lld + ThinLTO + fprofile-generate causes duplicate symbol errors

The duplicate symbol errors are for __llvm_profile_filename and
__llvm_profile_raw_version.
IIUC, these are supposed to be weak symbols but Thin LTO seems to break
this in some way.  This does't happen with gold or no LTO or full LTO.

$ cat > a.c
extern int foo();

int main() {
  return foo();
}

$ cat > b.c
int foo() {
  return 0;
}

$ clang a.c -fprofile-generate -flto=thin -c
$ clang b.c -fprofile-generate -flto=thin -c
$ clang a.o b.o -fprofile-generate -flto=thin -fuse-ld=lld
ld.lld: error: duplicate symbol: __llvm_profile_filename
>>> defined at a.c
>>>            lto.tmp:(__llvm_profile_filename)
>>> defined at b.c
>>>            lto.tmp:(.rodata.__llvm_profile_filename+0x0)
ld.lld: error: duplicate symbol:
__llvm_profile_raw_version
>>> defined at a.c
>>>            lto.tmp:(__llvm_profile_raw_version)
>>> defined at b.c
>>>            lto.tmp:(.rodata.__llvm_profile_raw_version+0x0)
clang-7: error: linker command failed with exit code 1 (use -v to see
invocation)
Makefile:10: recipe for target 'a.out' failed
make: *** [a.out] Error 1
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Hi Pirama,

I can't reproduce with either lld or gold, using a compiler built from
head. What version is your clang?

Thanks,
Teresa

On Tue, May 8, 2018 at 7:50 PM Pirama Arumuga Nainar via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> The duplicate symbol errors are for __llvm_profile_filename and
__llvm_profile_raw_version.
> IIUC, these are supposed to be weak symbols but Thin LTO seems to break
> this in some way.  This does't happen with gold or no LTO or full LTO.
>
> $ cat > a.c
> extern int foo();
>
> int main() {
>   return foo();
> }
>
> $ cat > b.c
> int foo() {
>   return 0;
> }
>
> $ clang a.c -fprofile-generate -flto=thin -c
> $ clang b.c -fprofile-generate -flto=thin -c
> $ clang a.o b.o -fprofile-generate -flto=thin -fuse-ld=lld
> ld.lld: error: duplicate symbol: __llvm_profile_filename
> >>> defined at a.c
> >>>            lto.tmp:(__llvm_profile_filename)
> >>> defined at b.c
> >>>            lto.tmp:(.rodata.__llvm_profile_filename+0x0)
>
> ld.lld: error: duplicate symbol: __llvm_profile_raw_version
> >>> defined at a.c
> >>>            lto.tmp:(__llvm_profile_raw_version)
> >>> defined at b.c
> >>>            lto.tmp:(.rodata.__llvm_profile_raw_version+0x0)
> clang-7: error: linker command failed with exit code 1 (use -v to see
> invocation)
> Makefile:10: recipe for target 'a.out' failed
> make: *** [a.out] Error 1
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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On Wed, May 9, 2018 at 6:43 AM Teresa Johnson <tejohnson at google.com>
wrote:
> Hi Pirama,
>
> I can't reproduce with either lld or gold, using a compiler built from
> head. What version is your clang?
>
(and your lld)

>
> Thanks,
> Teresa
>
> On Tue, May 8, 2018 at 7:50 PM Pirama Arumuga Nainar via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> The duplicate symbol errors are for __llvm_profile_filename and
__llvm_profile_raw_version.
>> IIUC, these are supposed to be weak symbols but Thin LTO seems to break
>> this in some way.  This does't happen with gold or no LTO or full
LTO.
>>
>> $ cat > a.c
>> extern int foo();
>>
>> int main() {
>>   return foo();
>> }
>>
>> $ cat > b.c
>> int foo() {
>>   return 0;
>> }
>>
>> $ clang a.c -fprofile-generate -flto=thin -c
>> $ clang b.c -fprofile-generate -flto=thin -c
>> $ clang a.o b.o -fprofile-generate -flto=thin -fuse-ld=lld
>> ld.lld: error: duplicate symbol: __llvm_profile_filename
>> >>> defined at a.c
>> >>>            lto.tmp:(__llvm_profile_filename)
>> >>> defined at b.c
>> >>>            lto.tmp:(.rodata.__llvm_profile_filename+0x0)
>>
>> ld.lld: error: duplicate symbol: __llvm_profile_raw_version
>> >>> defined at a.c
>> >>>            lto.tmp:(__llvm_profile_raw_version)
>> >>> defined at b.c
>> >>>           
lto.tmp:(.rodata.__llvm_profile_raw_version+0x0)
>> clang-7: error: linker command failed with exit code 1 (use -v to see
>> invocation)
>> Makefile:10: recipe for target 'a.out' failed
>> make: *** [a.out] Error 1
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
> --
> Teresa Johnson |  Software Engineer |  tejohnson at google.com |
>  408-460-2413
>

-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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