I just encountered this exact same problem, and this question came up during a Google search for the solution, so I'll document my dodgy solution here:
In the end I got it going just by making multiple small edits to the Assimp source code. Solving the string problem isn't enough to get it to work because it just fails later in the build. I'll list the edits I made below. I recommend making them one at a time and then rebuilding, just in case for whatever reason with your setup some of them aren't required. Note that you can't do model exporting with this solution because of the last edit (to Exporter.cpp) if you really need that you'll have to figure out another way to fix the link errors.
It's not a clean solution and it will probably be superceded by a future version of Assimp, at which point I will just delete it. This is for assimp-3.3.1, built with MinGW:
In StringComparison.h, edit the ASSIMP_stricmp function, commenting out everything except the else clause of the #ifdef:
/*#if (defined _MSC_VER)
return ::_stricmp(s1,s2);
#elif defined( __GNUC__ )
return ::strcasecmp(s1,s2);
#else*/
char c1, c2;
do {
c1 = tolower(*s1++);
c2 = tolower(*s2++);
}
while ( c1 && (c1 == c2) );
return c1 - c2;
//#endif
Do a similar thing in ASSIMP_strincmp.
Next, it throws up an error about ::_fullpath in DefaultIOSystem.cpp. My "fix" for this was just to use comment out everything other the fallback option in this function:
ai_assert(in && _out);
// char* ret;
//#if defined( _MSC_VER ) || defined( __MINGW32__ )
// ret = ::_fullpath( _out, in, PATHLIMIT );
//#else
// use realpath
// ret = realpath(in, _out);
//#endif
// if(!ret) {
// preserve the input path, maybe someone else is able to fix
// the path before it is accessed (e.g. our file system filter)
// DefaultLogger::get()->warn("Invalid path: "+std::string(in));
strcpy(_out,in);
// }
It also complains about snprintf being undefined. Edit StringUtils.h to change the following #define to add an underscore before snprintf:
# define ai_snprintf _snprintf
There's also an error about ::atof not being defined. You can fix this by adding
#include <cstdlib>
to StringUtils.h
This should get it building but there will be a link error in Exporter.cpp (this might be due to my specific CMake setttings because I disabled almost all model formats). I fixed it by commenting out the definition of gExporters and replacing it with this:
Exporter::ExportFormatEntry* gExporters = 0;
After this it built and ran fine. The library files are placed in the code folder. Place libassimp.dll.a in your lib build path and libassimp.dll in the path of your executable.
Of course, you can also get it going by using VisualStudio instead (I didn't because I couldn't be bothered installing it) or by building on Linux (I did this previously and it built fine first go, but I needed to do a Windows port).
