On Wed, Mar 16, 2011 at 11:43 AM, David Nadlinger <code at klickverbot.at>
wrote:> There is a description of all the possible linkage types at
> http://llvm.org/docs/LangRef.html#linkage – does this answer your
> question? (Basically, an extern_weak resp. ExternalWeakLinkage symbol
> becomes null instead of being an undefined reference)
>
Well, I was trying to know what in source gets to be translated to
WeakAnyLinkage or ExternalWeakLinkage.
I recently had a problem related to weak linkage handling in llvm on
WIndows 7. Here is the problem. I have
two files: m.c and foo.c
m.c
-----
#include <stdio.h>
__attribute__ ((weak)) int foo (void)
{
printf ("weak foo()\n");
return 1;
}
int main()
{
return foo();
}
foo.c
-----
#include <stdio.h>
int foo (void)
{
printf ("strong foo()\n");
return 2;
}
ubuntu linux
%llvm-gcc m.c foo.c; ./a.out
strong foo()
%llvm-gcc m.c; ./a.out
weak foo()
which is what I expect. However, on windows 7, llvm-gcc (built using
mingw) gives:
mingw/msys
%llvm-gcc m.c; ./a.exe
weak foo()
%llvm-gcc m.c foo.c
C:/Users/jugu/AppData/Local/Temp/ccGcz9jg.o:fake:(.text+0x0):
multiple definition of `foo'
C:/Users/jugu/AppData/Local/Temp/ccUZmVfP.o:fake:(.text$foo[_foo]+0x0):
first defined here
collect2: ld returned 1 exit status
which is not what I expect. Somehow, "weak" is missing.
m.s generated by this mingw llvm-gcc is
.section .text$foo,"xr"
.linkonce discard
.globl _foo
.align 16, 0x90
_foo:
Lllvm$workaround$fake$stub$_foo:
"weak' isn't there! It is a bug, no ?
(By the way, the older llvm generates the folloiwng for a code similar to m.c
.section .text$linkonce_foo,"xrn"
.linkonce same_contents
.globl _foo
I think that the section flag "xrn" is wrong, and
"n" should
not be there, and fortunately, this got fixed in the latest llvm)
Thanks
Junjie
> David
>
>
> On 3/16/11 7:06 PM, Junjie Gu wrote:
>> What is the difference between WeakAnyLinkage and ExternalWeakLinkage
>> ? They are defined in GlobalValue.h. Thanks
>>
>> Junjie
>> _______________________________________________
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>
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