Re: Create dll using gcc

[Igor Pechtchanski <pechtcha@cs.nyu.edu>]

On Tue, 2 Sep 2003, Christian Neise wrote:

> Hello,
>
> i am trying to build a dll using cygwin and gcc. The dll will be used
> by a delpi application.
>
> The dll works fine. But when allocating memory
> (e.g.: char *c = new char) the programm crashes.
>
> When compiling the dll with visual c++ 6.0 SP5 the dll works fine -
> even if allocating memory.
>
> Any hints?
>
> Best regards,
>
> Christian Neise
>
> P.S.:
>
> I createdthe dll the following way:
> gcc  -c dll_test.cpp -o debug/dll_test.o
> gcc   -shared -o debug/dll_test.dll \
> -L/usr/lib \
> -Wl,--export-all-symbols \
> -Wl,--enable-auto-import \
> -Wl,--whole-archive debug/dll_test.o \
> -L/usr/lib \
> -Wl,--no-whole-archive -lc -lstdc++
>
>
> testdll.h:
>
> #include <string>
>
>  extern "C" {
>       __declspec( dllexport ) BOOL APIENTRY DllMain( HANDLE hModule,
>                             DWORD  ul_reason_for_call,
>                             LPVOID lpReserved
>          );
>  }
>
>
>
>
> testdll.cpp:
>
> #include "dll_test.h"
>
> BOOL APIENTRY DllMain( HANDLE hModule,
>                        DWORD  ul_reason_for_call,
>                        LPVOID lpReserved
>                                          )
> {
>     switch (ul_reason_for_call)
>         {
>                 case DLL_PROCESS_ATTACH:
>                 case DLL_THREAD_ATTACH:
>                 case DLL_THREAD_DETACH:
>                 case DLL_PROCESS_DETACH:
>                         break;
>     }
>     return TRUE;
> }

The DLL you created will require cygwin1.dll as its C runtime library.
The Delphi application most likely uses MSVCRT.DLL as it's C runtime.
It's not a good idea to mix the two runtimes (in fact, that's the most
likely reason for the crashes).  If you want to use your DLL with Delphi,
you could compile it using MinGW (by passing the "-mno-cygwin" option to
gcc), but you won't get full POSIX emulation that way.
	Igor
-- 
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