Linking VC++ DLL

[Hannu E K Nevalainen (garbage mail)]

> From: cygwin-owner@cygwin.com [mailto:cygwin-owner@cygwin.com]On Behalf

--8<--
> extern "C" __declspec(dllexport) int hello()
> {
> 	printf("Hello World!\n");
> 	return 345;
> }

--8<--
> int main()
> {
> 	printf("What is this? %d\n", hello());
> }
>
> All I get in return is (under Cygwin):
> What is this? 345
>
> 345 demonstrates that the function was called and correctly returned but
> why is it that the printf statement in the function hello() went missing?
> I have tried to run other VC compiled program but had no problem in
> getting printf statements to work under the Cygwin environment. Would
> appreciate if anyone can suggest what could be the possible
> problem. Thanks!
>
> regards
> Edward

I believe this is close to off topic on the cygwin list. ;-)

 My guess is that stdin/stdout from main() isn't defined/visible for the
functions inside your library.

To illustrate the problem; Try this:
--8<--
extern "C" __declspec(dllexport) int hello(FILE *of)
{
	fprintf(of,"Hello World!\n");
	return 345;
}

--8<--
int main()
{
	printf("What is this? %d\n", hello(stdout));
}
--8<--

... which MIGHT work.

Expect something like:
  Hello World!
  What is this? 345
as output.

You may have a problem here:
 I believe you have to think about which version of printf() you wish to
have available in your library and/or program.
 Your library might contain *a copy of printf()*, I'm not sure it will be
sufficient for all situations. Especially as it seems as you're using two
different compilers/environments to compile your library and program.

If so; IMHO there is great potential for serious malfunction.

/Hannu E K Nevalainen, Mariefred, Sweden

--END OF MESSAGE--



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