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Date: Thu, 5 Jul 2001 22:20:43 -0700 (PDT)
From: Mo DeJong <mdejong AT cygnus DOT com>
To: cygwin AT sources DOT redhat DOT com
Subject: Problem choosing exe entry point.
Message-ID: <Pine.SOL.3.91.1010705215806.2695B-100000@cse.cygnus.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

Hi all.

I think I have found a problem with the way Cygwin ld
picks the executable entry point when both WinMain() and main()
are available. I would think that passing in the -mwindows flag
(which gets passed to ld as --subsystem windows) would clear
things up and link with WinMain(). Instead, Cygwin ld is
choosing main().

Here is a quick example to demonstrate the problem:

% cat t2.c         
#include <windows.h>
#include <winbase.h>
#include <winuser.h>

int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int nCmdShow) {
  return 1;
}

int main() {       
  return 0;
}

/* End of t2.c */



Compiled with VC++:

% cl -c t2.c -MD
% link /Out:t2 t2.obj -subsystem:windows msvcrt.lib
% ./t2.exe 
% echo $?
1

(The above uses WinMain() as the entry point, as expected)

Compiled with Cygwin gcc.

% gcc -mwin32 -c t2.c
% gcc -mwindows -o t2 t2.o
/usr/lib/gcc-lib/i686-pc-cygwin/2.95.3-2/../../../../i686-pc-cygwin/bin/ld:
warning: cannot find entry symbol _WinMainCRTStartup; defaulting to 00401000
% ./t2.exe 
% echo $?
0

(Note how main() was used as the entry point above)


The workaround is to explicitly pass in the WinMain() entry point:

% gcc -mwindows -o t2 t2.o -e _WinMain AT 16
% ./t2.exe
% echo $?
1

Does this seem like a bug in ld to anyone else?
I would think that passing "--subsystem windows"
should make it default to WinMain() while passing
"--subsystem console" would make it default to
main(). Does that seem reasonable?

Mo DeJong
Red Hat Inc

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