Thanks Matthew <div class="gmail_quote">On Sun, Nov 27, 2011 at 6:59 PM, Matthew Flatt <<a href="mailto:mflatt@cs.utah.edu">mflatt@cs.utah.edu</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"> <div class="im">At Sun, 27 Nov 2011 18:20:46 -0500, Harry Spier wrote: > Dear list members, > On going through the article on the FFI by Eli Barzilay and Dmitry Orlovsky > <a href="http://www.ccs.neu.edu/scheme/pubs/scheme04-bo.pdf" target="_blank">http://www.ccs.neu.edu/scheme/pubs/scheme04-bo.pdf</a> > > It says: > "libffi is maintained and distributed as part of the GCC project, > but its goal is to provide a portable library. We use it for all > platforms that PLT Scheme targets, including Windows (using a > slightly adapted version that works with Microsoft’s compiler, courtesy > of the Thomas Heller [13])." </div>(Racket now uses the main libffi sources for Windows, too.) <div class="im"> > Does that mean that if I'm using the Windows version of Racket and I want > to use the FFI to interface to ImageMagick, that the ImageMagick Windows > executable must also be compiled with the microsoft C compiler rather than > with MingW GCC ? </div>No. <div class="im"> > A few years ago when I interfaced ImageMagick to Ruby using Ruby's > ImageMagick interface "RMagick" there was a problem for a while about > RMagick being compiled with Microsoft Visual C compiler (it may have been a > particular version of the Visual C compiler?) and I think the ImageMagick > executable for windows was compiled with MingW GCC. The problem was > resolved when the RMagick interface was compiled using the same compiler as > ImageMagick. </div>That sounds like an issue with mismatched C runtime libraries. The main way a mismatch can show up with Racket's FFI is when a foreign function allocates a value, and the caller is supposed to free it with free(). In that case, calling the Racket `free' function may not work, because it may use a different memory allocator from the one linked to the foreign library --- i.e., different instances of malloc() and free() from different C libraries. Most libraries that provide allocation functions also provide corresponding deallocation functions instead of relying on free(), and that avoids the problem. Meanwhile, Racket uses "msvcrt.dll" as its C runtime library, which is consistent with most binary distributions of open-source software. I believe that MinGW binaries by default use "msvcrt.dll". For all of those reasons, you probably won't run into problems due to a compiler mismatch when using Racket's FFI. </blockquote></div>