Related : [[C]] [[CPlusPlus]] [[GCC]] [[Cygwin]] [[MSVC]]

Mixing compiled objects between [[GCC]] and [[MSVC]] does work at least when shared code is in [[C]], [[C++]] is causing trouble on different name mangeling.


===Sample code===

cat cplusplus.h << EOF
  #ifndef CPlusPlus_h_
  #define CPlusPlus_h_

  #define API

  class API CPlusPlus { public: static int f(int in); };
  extern "C" {
   API int fglobal(int in);
   API CPlusPlus* getInstanceCPlusPlus();
  }
  #endif
EOF

cat cplusplus.cpp  << EOF
  #include "cplusplus.h"
  int CPlusPlus::f(int in) { return in; }
  int fglobal(int in) { return in; }
EOF

cat main.cpp  << EOF
  #include <cstdlib>
  #include <iostream>
  using namespace std;
  #include "cplusplus.h"
  int main(int argc,char* argv[[]]) {
   cout << "# " <<fglobal(argc)<< endl;  // C link : works : 00000008 T _fglobal
   CPlusPlus * p = 0; p = new CPlusPlus; // C++ link : works
  #ifdef BUG // C++ link : fails : ====  name mangeling between gcc and msvc===
   cout <<  p->f(argc) << endl;
   // printf("# %d\n", getInstanceCppModule()->f(argc) );
  #endif // @see http://cygwin.com/ml/cygwin/2005-03/msg00413.html
   return EXIT_SUCCESS;
  }
EOF

===Static lib link :===
  g++ -c -o ./cplusplus.o -mno-cygwin -mwindows -g -I. -Dcygwin -D_GNU_SOURCE -I. ./cplusplus.cpp
  ar rcu ./libcplusplus.lib cplusplus.o

  cl.exe /c /EHsc /nologo  main.cpp

  link.exe \
  /INCREMENTAL /NOLOGO /MACHINE:X86 /DEBUG /SUBSYSTEM:CONSOLE \
  /OUT:"cplusplus.exe" /LIBPATH:"." main.obj libcplusplus.lib

  cplusplus.exe *
  # 15


  ldd cplusplus.exe
  h:/src/cplusplus/cplusplus.exe

   C:\WINDOWS\System32\KERNEL32.dll

     C:\WINDOWS\System32\ntdll.dll


===Static lib with C++ method===
  rm main.obj
  cl.exe /c /EHsc /nologo /DBUG main.cpp


  cc-msvc.sh  link.exe \
  /INCREMENTAL /NOLOGO /MACHINE:X86 /DEBUG /SUBSYSTEM:CONSOLE \
  /OUT:"cplusplus.exe" /LIBPATH:"." main.obj libcplusplus.lib
  main.obj : error LNK2019: unresolved external symbol
  "public: static int __cdecl CPlusPlus::f(int)" (?f@CPlusPlus@@SAHH@Z)
   referenced in function _main

  cplusplus.exe : | error LNK1120: 1 unresolved externals


  nm libcplusplus.lib ;
  cplusplus.o:
  00000000 b .bss
  00000000 d .data
  00000000 N .stab
  00000000 N .stabstr
  00000000 t .text
  00000000 T __ZN9CPlusPlus1fEi
  00000008 T _fglobal

For obscure reasons, the mangling name are different

===Conclusion===

So Why it is impossible to link [[C++]] [[GCC]]'s objects coming with [[MSVC]] ?

http://cygwin.com/ml/cygwin/2005-03/msg00413.html

Can dynamic libs workaround this ?

I doubt [[GCC]] can write a compatible [[MSVC]] "library stub" ( XYZ.lib that goes along XYZ.dll, not a static one : libXYZ.lib )

But maybe runtime linking is possible ... I am investigating on this...

[[ToDo]]

===MISC===

Thanks go to : Arend-Jan Westhoff, Christopher Faylor, Jonathan Arnold, Tim Prince and all the [[Cygwin]] pple.

Some additional info:

<http://www.network-theory.co.uk/docs/gccintro/gccintro_65.html>
<http://www.network-theory.co.uk/docs/gccintro/gccintro_16.html>
<http://www.linuxquestions.org/questions/archive/9/2003/10/3/105795>
<http://www.linuxlookup.com/HOWTO/GCC-HOWTO/x575.html#AEN579>

<http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/html/_core_lib_reference.asp>

<http://www.cygwin.com/faq/faq_3.html#SEC103>
<http://www.cygwin.com/faq/faq_3.html#SEC102>