llvm dev - Sep 2010 - [LLVMdev] Cross-compiling LLVM with llvm-gcc produces a lot of warnings

Hi,

I'm cross compiling (BUILD=darwin, HOST=i386-mingw32) LLVM with
llvm-gcc (both from current mainline). Everything works fine,
except that I get a lot of warnings of the following type:

[..]/lib/gcc/i386-mingw32/4.2.1/../../../../i386-mingw32/bin/ld:
/[..]/build-llvm/Release/lib/libLLVMSupport.a(APInt.o): warning:
duplicate section
`.text$linkonce__ZN4llvm5APInt17getSignedMinValueEj' has
different size

/[..]/lib/gcc/i386-mingw32/4.2.1/../../../../i386-mingw32/bin/ld:
/[..]/build-llvm/Release/lib/libLLVMSupport.a(APInt.o): warning:
duplicate section
`.text$linkonce__ZN4llvm5APInt17getSignedMaxValueEj' has
different size

/[..]/lib/gcc/i386-mingw32/4.2.1/../../../../i386-mingw32/bin/ld:
/[..]/build-llvm/Release/lib/libLLVMSupport.a(APInt.o): warning:
duplicate section `.text$linkonce__ZN4llvm5APIntlSEj' has
different size

/[..]/lib/gcc/i386-mingw32/4.2.1/../../../../i386-mingw32/bin/ld:
/[..]/build-llvm/Release/lib/libLLVMSupport.a(APInt.o): warning:
duplicate section `.text$linkonce__ZNK4llvm5APIntngEv' has
different size

Is this normal/known?

> /[..]/lib/gcc/i386-mingw32/4.2.1/../../../../i386-mingw32/bin/ld:
> /[..]/build-llvm/Release/lib/libLLVMSupport.a(APInt.o): warning:
> duplicate section `.text$linkonce__ZNK4llvm5APIntngEv' has
> different size
>
> Is this normal/known?
Yes, this is known problem. In fact it was here for ages, but
previously we just grabbed
one "instance" of linkonce function without checking whether other
copies are the same.
Starting from May we're also checking for the contents and thus this
warning appeared.

Two copies of the linkonce function in question are almost identical,
however, one has all
EH stuff and other - don't. I haven't looked yet who is responsible
for this problem, but my
current assumption that this is a frontend fault.

Same problem can be seen via just libstdc++ compilation on mingw32.

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University

Btw, with optimizations multiple copies of linkonce function can
easily diverge. A trivial example is

// a.h
int foo(int x);

inline int bar(int x) { return foo(x); }

// a.cpp
#include "a.h"

int foo(int x) { return 1; }

// b.cpp
#include "a.h"

Out-of-line copies of bar() in a.cpp and b.cpp will be different,
because in a.cpp foo() is likely to get inlined.

Eugene

On Fri, Sep 3, 2010 at 5:43 PM, Anton Korobeynikov
<anton at korobeynikov.info> wrote:
>> /[..]/lib/gcc/i386-mingw32/4.2.1/../../../../i386-mingw32/bin/ld:
>> /[..]/build-llvm/Release/lib/libLLVMSupport.a(APInt.o): warning:
>> duplicate section `.text$linkonce__ZNK4llvm5APIntngEv' has
>> different size
>>
>> Is this normal/known?
> Yes, this is known problem. In fact it was here for ages, but
> previously we just grabbed
> one "instance" of linkonce function without checking whether
other
> copies are the same.
> Starting from May we're also checking for the contents and thus this
> warning appeared.
>
> Two copies of the linkonce function in question are almost identical,
> however, one has all
> EH stuff and other - don't. I haven't looked yet who is responsible
> for this problem, but my
> current assumption that this is a frontend fault.
>
> Same problem can be seen via just libstdc++ compilation on mingw32.
>
> --
> With best regards, Anton Korobeynikov
> Faculty of Mathematics and Mechanics, Saint Petersburg State University
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