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Date: Mon, 7 Jun 2004 15:38:21 +0100 (GMT Daylight Time)
From: Alastair Growcott <Alastair DOT Growcott AT bakbone DOT co DOT uk>
Subject: Re[5]: Visual Studio linking
To: cygwin AT cygwin DOT com
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To all those who said it couldn't be done...I've done it :)

Hahahaha.

Seriously, it is quite easy once you figure it out, and I am sure there are plenty of people who helped write Cygwin who probably knew but couldn't be bothered to tell me.

It involves a couple of minor hacks. It would be nice if cygwin1.dll could export the cygwin_crt0() function.

Here is how you do it:

1) Use the impdef program to generate a .def file for the cygwin1.dll
    impdef cygwin1.dll > cygwin1.def

2) Use the MS VS linker (lib) to generate an import library
    lib /def=cygwin1.def /out=cygwin1.lib

3) Create a file "my_crt0.c" with the following contents
  
#include <sys/cygwin.h>
#include <stdlib.h>

typedef int (*MainFunc) (int argc, char *argv[], char **env);

void
my_crt0 (MainFunc f)
{
  cygwin_crt0(f);
}

4) Use gcc in a Cygwin prompt to build my_crt0.c into a DLL (e.g. my_crt0.dll). Follow steps 1 and 2 to generate .def and .lib files for the DLL.

5) Download crt0.c from the cygwin website and include it in your sources. Modify it to call my_crt0() instead of cygwin_crt0().

6) Build your object files using the MS VC compiler cl.

7) Link your object files, cygwin1.lib, and my_crt0.lib (or whatever you called it) into the executable.

Note that if you are using any other Cygwin based libraries that you will probably need to build them as DLLs using gcc and then generate import libraries for the MS VC linker.

Alastair.





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