[cfe-commits] r133450 - in /cfe/trunk: lib/CodeGen/CodeGenModule.cpp lib/Sema/SemaDecl.cpp test/CodeGen/attr-weak-import.c

[jahanian]

On Jun 21, 2011, at 3:22 PM, Eli Friedman wrote:

> On Mon, Jun 20, 2011 at 10:50 AM, Fariborz Jahanian <fjahanian at apple.com> wrote:
>> Author: fjahanian
>> Date: Mon Jun 20 12:50:03 2011
>> New Revision: 133450
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=133450&view=rev
>> Log:
>> llvm-gcc treats a tentative definition with a previous
>> (or follow up) extern declaration with weak_import as
>> an actual definition. make clang follows this behavior.
>> // rdar://9538608
>> llvm-gcc treats an extern declaration with weak_import
>> 
>> Added:
>>    cfe/trunk/test/CodeGen/attr-weak-import.c
>> Modified:
>>    cfe/trunk/lib/CodeGen/CodeGenModule.cpp
>>    cfe/trunk/lib/Sema/SemaDecl.cpp
>> 
>> Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=133450&r1=133449&r2=133450&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
>> +++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Mon Jun 20 12:50:03 2011
>> @@ -1351,7 +1351,8 @@
>>            ((!CodeGenOpts.NoCommon && !D->getAttr<NoCommonAttr>()) ||
>>              D->getAttr<CommonAttr>()) &&
>>            !D->hasExternalStorage() && !D->getInit() &&
>> -           !D->getAttr<SectionAttr>() && !D->isThreadSpecified()) {
>> +           !D->getAttr<SectionAttr>() && !D->isThreadSpecified() &&
>> +           !D->getAttr<WeakImportAttr>()) {
>>     // Thread local vars aren't considered common linkage.
>>     return llvm::GlobalVariable::CommonLinkage;
>>   }
>> 
>> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=133450&r1=133449&r2=133450&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Mon Jun 20 12:50:03 2011
>> @@ -2039,6 +2039,12 @@
>>   }
>> 
>>   mergeDeclAttributes(New, Old, Context);
>> +  // weak_import on current declaration is applied to previous
>> +  // tentative definiton.
>> +  if (New->getAttr<WeakImportAttr>() &&
>> +      Old->getStorageClass() == SC_None &&
>> +      !Old->getAttr<WeakImportAttr>())
>> +    Old->addAttr(::new (Context) WeakImportAttr(SourceLocation(), Context));
> 
> Applying attributes backwards is generally not how we do things... we
> can't in general apply attributes backwards (even if it might happen
> to work here to some extent).  Is this really necessary?

Unfortunately yes. Need to make this test compatible with llvm-gcc:

int C;
extern int C __attribute__((weak_import));

% llvm-gcc -c t.c
% nm -nm t.o
0000000000000000 (__DATA,__common) external _C
% $CLANG -c t.c
% nm -nm t.o
0000000000000000 (__DATA,__common) external _C

- Fariborz



> 
> -Eli