This is the mail archive of the
cygwin@sourceware.cygnus.com
mailing list for the Cygwin project.
Re: DLL Problem
- To: geier at forwiss dot uni-passau dot de (Roland Geier)
- Subject: Re: DLL Problem
- From: Fergus Henderson <fjh at cs dot mu dot OZ dot AU>
- Date: Mon, 25 Aug 1997 16:13:16 +1000 (EST)
- Cc: gnu-win32 at cygnus dot com (Cygnus GNU-win32 mailing list)
Roland Geier wrote:
> [someone wrote:]
> > I'm trying to port a tcl module from unix to win95 as a dll to load within
> > wish.
...
> > ext+0x15):libcmain.cc: undefined reference to `GetCommandLineA@0'
> > c:/gnuwin32/b18/H-i386-cygwin32/i386-cygwin32/lib/libcygwin.a(libcmain.o)(.t
> >
> > ext+0x1e):libcmain.cc: undefined reference to `WinMain@16'
> >
> > This seems to be a reentrancy problem, since a simple call like :
> > fprintf(stderr, ...)
>
> ...for me this seems to be a forgotten '-lkernel32' at link-time :). The
> undefined ref to 'WinMain' can be avoided with:
>
> echo 'int main() { return 0; }' > fixup.c;
> echo 'asm (".section .idata$3\n" ".long 0,0,0,0,0,0,0,0");' >> fixup.c;
> gcc -c fixup.c
> # link fixup.o with your dll...
Defining main() will supress the link error, but it will not actually
fix the problem. The startup file (crt0.o, I think) containing a
definition of `_impure_ptr' will be linked in, but _impure_ptr will
not be initialized. This means that any reference to global variables
such as `stdout' or `stderr' from within your DLL will be broken, and
so your DLL will probably crash.
To avoid the problem, you need to initialize your DLL's _impure_ptr
from the main program. See <http://www.cs.mu.oz.au/~fjh/gnu-win32>
for an example of how to do this.
--
Fergus Henderson <fjh@cs.mu.oz.au> | "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh> | of excellence is a lethal habit"
PGP: finger fjh@128.250.37.3 | -- the last words of T. S. Garp.
-
For help on using this list (especially unsubscribing), send a message to
"gnu-win32-request@cygnus.com" with one line of text: "help".