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Carl

2014-Feb-10 14:28 UTC

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

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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Reid Kleckner

2014-Feb-10 18:44 UTC

head link

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

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.
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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Carl

2014-Feb-11 12:16 UTC

head link

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

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.
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>>
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llvm dev - Feb 2014 - [LLVMdev] Fwd: [windows) how to use weak references with llvm 3.4 and windows?

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

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

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