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Subject: RE: undefined reference to `__imp___iob'
Date: Tue, 26 Jun 2007 13:13:12 -0400
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From: "Frederich, Eric P21322" <eric DOT frederich AT siemens DOT com>
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> From: cygwin-owner AT cygwin DOT com 
> [mailto:cygwin-owner AT cygwin DOT com] On Behalf Of Brian Dessent
> Sent: Tuesday, June 26, 2007 12:22 PM
> To: cygwin AT cygwin DOT com
> Subject: Re: undefined reference to `__imp___iob'
> 
> "Frederich, Eric P21322" wrote:
> 
> > Are there any tips to compile compatible libraries with 
> msys / cygwin?
> > Is it even possible?
> > Am I missing a gcc option?
> 
> No, it's not possible.
> 
> Cygwin libraries use the Cygwin runtime.  MinGW/MSYS libraries use the
> Microsoft (MSVCRT) runtime.  These are two inherently different and
> incompatible implementations of a C runtime, so you can't 
> link a program
> that uses both and expect it to work.
> 
> It is technically possible if you are very sure of what you're doing,
> but this would involve making sure that all C functions are 
> resolved to
> the correct library.   For example, printf() in the MinGW code must go
> to MSVCRT, printf() in the Cygwin code must go to 
> cygwin1.dll.  The only
> way I can think to do this is with LoadLibrary()/GetProcAddress() and
> function pointers for everything.  It also would mean that no 
> C library
> data structures could be passed between the two, such as file
> descriptors, FILE *, struct stat, etc.  It would be an extremely
> inconvent way to write code, and it would be much easier and 
> cleaner to
> just compile all code as Cygwin code or all code as native (MSVCRT)
> code.
> 
> Brian

Thanks for your reply.
Does everything you say hold true even if I compile with the -mno-cygwin
option?

The program I was talking about linked to 4 libraries so I made a small
main.c and just tried adding one library at a time.  I wrote a small
program to link against a single library and it worked.  I was passing
around FILE pointers and that worked okay too.  From main.c I did the
fopen and fclose and wrote to the file using the msys/mingw compiled
library.  Was I just lucky?
When I tried adding in another library I got those errors again.

Apparently I'm confused.  I thought that when I compile with -mno-cygwin
it was the same as using msys/mingw.

Thanks,
~Eric

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