[LLVMdev] Fwd: [windows) how to use weak references with llvm 3.4 and windows?

[Carl]

Thanks for your clear answer. Do you know what modifier should I use to
declare such weak symbols in my llvm intermediate code?

So that it can be compiled to the .o file with the weak attribute ?
Le 10 févr. 2014 19:44, "Reid Kleckner" <rnk at google.com> a écrit :

> COFF doesn't support the same kind of concept of 'weak' that ELF does.
>  This is the issue that users brought up with mingw:
> https://sourceware.org/bugzilla/show_bug.cgi?id=9687
>
> Instead, COFF supports weak externals, which you can use like:
>
> $ cat t.c
> int foo() __attribute__((weak));
> int main() {
>   if (foo)
>     return foo();
>   return 13;
> }
>
> $ cat t2.c
> int foo() {
>   return 42;
> }
>
> $ clang t.c t2.c -o t && ./t ; echo $?
> 42
>
> So, we got the definition of foo from t2.c.  If t2.c hadn't been linked,
> foo would be null.
>
>
> On Mon, Feb 10, 2014 at 6:28 AM, Carl <name.is.carl at gmail.com> wrote:
>
>>
>> Hello,
>>
>> I'm generating C code (and the resulting obj files) using llvm 3.4 for
>> both unix and windows.
>> And I use the dreaded weak references, that, for windows, are not too
>> widely supported.
>>
>> When I link my application on linux, I have no issue.
>> But when I'm doing the same on windows using mingw I got a duplicate
>> symbol error :
>>
>> ..\robovm-0.0.8\lib\robovm-rt.jar\dalvik\system\BlockGuard$BlockGuardPolicyException.class.o:(.text$dalvik_system_BlockGuard$24BlockGuardPolicyException_getPolicy__I_lookup[_dalvik_system_BlockGuard$24BlockGuardPolicyException_getPolicy__I_lookup]+0x0):
>> multiple definition of
>> `dalvik_system_BlockGuard$24BlockGuardPolicyException_getPolicy__I_lookup'
>> ..\Temp\robovm3774596063679264132.tmp\linker.o:(.text+0x340): first
>> defined here
>> ..\robovm-0.0.8\lib\robovm-rt.jar\dalvik\system\BlockGuard$BlockGuardPolicyException.class.o:(.text$dalvik_system_BlockGuard$24BlockGuardPolicyException_getPolicyViolation__I_lookup[_dalvik_system_BlockGuard$24BlockGuardPolicyException_getPolicyViolation__I_lookup]+0x0):
>> multiple definition of
>> `dalvik_system_BlockGuard$24BlockGuardPolicyException_getPolicyViolation__I_lookup'
>> ..\Temp\robovm3774596063679264132.tmp\linker.o:(.text+0x350): first
>> defined here
>> ..\robovm-0.0.8\lib\robovm-rt.jar\dalvik\system\BlockGuard$BlockGuardPolicyException.class.o:(.text$dalvik_system_BlockGuard$24BlockGuardPolicyException_getMessage__Ljava_lang_String$3B_lookup[_dalvik_system_BlockGuard$24BlockGuardPolicyException_getMessage__Ljava_lang_String$3B_lookup]+0x0):
>> multiple definition of
>> `dalvik_system_BlockGuard$24BlockGuardPolicyException_getMessage__Ljava_lang_String$3B_lookup'
>>
>> Because those symbols are declared as weak.
>>
>> What is the status about the support of weak symbols on windows?
>> Are they supposed to work? Are they supposed to *never *work ?
>>
>> Do you know any way to fix this (or work around it). I use weak symbols
>> everywhere in my code generation, so I would prefer a fix that doesn't
>> involve to rewrite my code.
>>
>> I'm considering rewriting the obj files using objcopy.
>> Has this any chance to work ?
>> Here are the o.
>>
>> Cheers,
>> Carl.
>>
>>
>> _______________________________________________
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>>
>>
>
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