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To: cygwin@cygwin.com
From: Soren Hein <soren.hein@gmail.com>
Subject: cygwin DLL and mingw main
Date: Mon, 30 Jun 2014 12:25:03 +0000 (UTC)
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Below are (1) a simple dll (dds.dll) and (2) a simple main program 
(dtest.cpp).  After much experimentation I have reduced my problem to this 
tiny test case.

If I compile (1) with cygwin and (2) with mingw, the resulting program 
segfaults when run.

(1) with cygwin and (2) with cygwin works.
(1) with mingw and (2) with mingw works.
(1) with mingw and (2) with cygwin works.

There are also combinations with Microsoft cl that work.

Why does it segfault?  It's driving me nuts.

g++ v4.8.3, mingw v4.8.2.
% uname -a
CYGWIN_NT-6.1-WOW64 CDD-NB01 1.7.30(0.272/5/3) 2014-05-23 10:36 i686 Cygwin


Thanks,
Soren
-----

% cat dds.cpp
#include <windows.h>
#include <stdio.h>

extern "C" __declspec(dllexport) int __stdcall identify()
{
  return 17;
}

% cat dtest.cpp
#include <windows.h>
#include <stdio.h>

extern "C" __declspec(dllimport) int __stdcall identify();

int main(int argc, char * argv[])
{
  printf("Return value is %d\n", identify());
  return TRUE;
}


This compilation leads to the fail:
g++ -o dds.dll -shared dds.cpp -Wl,--subsystem,windows
i686-w64-mingw32-g++ -o dtest dtest.cpp -Wl,--subsystem,windows -L./ -ldds

This compilation works:
i686-w64-mingw32-g++ -shared dds.cpp -Wl,--subsystem,windows -o dds.dll
g++ dtest.cpp -Wl,--subsystem,windows -L./ -ldds -o dtest


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