clang emits wrong section name for C++ symbols when targeting mingw32

[Quuxplusone]

Bugzilla Link	PR19222
Status	NEW
Importance	P normal
Reported by	Ivan Garramona (heavenandhell171@gmail.com)
Reported on	2014-03-21 13:08:08 -0700
Last modified on	2016-05-14 14:05:41 -0700
Version	trunk
Hardware	All All
CC	compnerd@compnerd.org, hlandau@devever.net, llvm-bugs@lists.llvm.org, rafael@espindo.la
Fixed by commit(s)
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I'm having problems with wxWidgets (static library) built with Clang (trunk +
Mingw-w64 4.8.2). The build of wxWidgets went fine, the problem is when i try
to link against it.

The wxWidgets -Os build doesn't work with static libstdc++. I get a "multiple
definition of `char* std::string::_S_construct<char*>(char*, char*,
std::allocator<char> const&, std::forward_iterator_tag)'" error.

The -O2/-O3 build works fine.

Here's a litle test case:

$ cat > Test.cpp
#include <string>
#include <sstream>

// This is a stripped version of the wxWidgets method.
std::string FromCDouble(double val, int precision) {
  std::ostringstream os;
  os << val;
  return os.str();
}

int main() {
  return 0;
}

$ clang++ -Os Test.cpp -std=c++11 -static
c:/dev/mingw32/bin/../lib/gcc/i686-w64-
mingw32/4.8.2/../../../../lib\libstdc++.a(string-
inst.o):(.text$_ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag[__ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag]+0x0):
multiple definition of `char* std::string::_S_construct<char*>(char*, char*,
std::allocator<char> const&, std::forward_iterator_tag)'
C:\Dev\MSys2\tmp\Test2-
525d5d.o:(.text[__ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag]+0x0):
first defined here
collect2.exe: error: ld returned 1 exit status
clang++.exe: error: linker (via gcc) command failed with exit code 1 (use -v to
see invocation)

[Quuxplusone]

I believe i've figured whats happening. The problem is not specific to
"_S_construct" or -Os. The problem is that the weak symbols generated by Clang,
have different section names than the ones generated by GCC. This is causing
incompatibilities.

Clang generate simple section names, like: .rdata or .text.
GCC generate sections like: .section$SymbolName. Note: The symbol name doesn't
have the '_' global prefix.

For example, this is one of the many multiple definitions i've got while trying
to build wxWidgets.

Original output:
.section    .rdata,"r",discard,_IID_IShellItem

Should be:
.section    .rdata$IID_IShellItem,"r",discard,_IID_IShellItem

This incompatibility may have been introduced by r195798 (to fix PR17918).

[Quuxplusone]

Also experiencing this issue. Here's a minimal test case which demonstrates the linker errors:

https://gist.github.com/hlandau/f6d77b2778e87a6d859940822775b8ca