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Re: impure_ptr/Mingw and Cygwin

On Fri, 22 Nov 2002, Andrew DeFaria wrote:

> I wish to use -mno-cygwin to produce an executable that can work without 
> Cygwin installed. I have successfully done this before. Now I'm adding 
> some functionality to my program and it is no longer working! I've 
> worked it out such that it will compile and link but when my program 
> runs it simply stops returning an exit code of 5. Running this under gdb 
> produces a SIGSIGV Segmentation fault then you attempt to run it.
> I've whittled it down to the bare minimum to reproduce the problem. 
> Seems to me the problem is somewhere between newer versions of gcc 3.X 
> and Mingw.
> File: foo.c:
> #include <stdio.h>
> int main (void) {
>   printf ("Hello World\n");
>   fprintf (stderr, "%s\n", "Hello World 2");
> }
> $ gcc -g foo.c -mno-cygwin -I/usr/include -o foo -liberty -lcrtdll -lg
> $ foo
> $
> Note that if I do not put -lg then I get:
> /tmp/ccKAyr4S.o(.text+0x4b): In function `main':
> /dview/defaria_2.0/salira/neopon/build/maketools/foo.c:4: undefined 
> reference to `_impure_ptr'
> Any ideas?

Well, for one thing, linking with -lg will pull in cygwin.dll since
/lib/libg.a is a symlink to libcygwin.a.  So your program won't be
Cygwin-free, if that's your goal.  However, I got it to work with the
following command:

$ gcc -g foo.c -mno-cygwin -mwindows -o foo -liberty -lmingw32
$ ./foo.exe > x
$ cat x
Hello World

If you change 'stderr' to 'stdout' you get "Hello World 2" in the output
too.  You'll have to play with carriage control a bit, but basically it
works.  Windows doesn't really have the concept of a stderr file handle,
so this behaviour makes sense to me.  I ran the resulting executable
through Visual C++'s DUMPBIN program and verified foo.exe only imports
msvcrt.dll and kernel32.dll, so it's Cygwin-free. 

Peter A. Castro <> or <>
	"Cats are just autistic Dogs" -- Dr. Tony Attwood

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