On Windows, if SDL is compiled targeting x86 and without a C runtime library the SDL_stlib.c defines a _chkstk symbol, but there are no actual instructions for this function.

This is not a problem if SDL is compiled as a dynamic library as it doesn't seem to generate any _chkstk calls. However, people want to link it statically now and their code might generate those calls which will cause the application to terminate pretty fast.

I would recommend everyone to compile SDL 2.0.0 with HAVE_LIBC defined and the Visual C++ runtime library when using MSVC and linking SDL statically on Windows x86.

Writing an actual implementation probably requires some knowledge about the Microsoft implementation. Copying theirs obviously has licensing issues.

Here's the disassembly that shows the issue in code form.

--- src\stdlib\sdl_stdlib.c -----------------------
SDL_toupper:
 mov         eax,dword ptr [esp+4]  
 lea         ecx,[eax-61h]  
 cmp         ecx,19h  
 ja          SDL_toupper+0Fh (0CC15DFh)  
 add         eax,0FFFFFFE0h  
 ret  
SDL_tolower:
 mov         eax,dword ptr [esp+4]  
 lea         ecx,[eax-41h]  
 cmp         ecx,19h  
 ja          SDL_tolower+0Fh (0CC15EFh)  
 add         eax,20h  
 ret  
_chkstk:
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
 int         3  
_ftol:
 push        ebp  
 mov         ebp,esp  
 sub         esp,20h  
 and         esp,0FFFFFFF0h  
 fld         st(0)  
 fst         dword ptr [esp+18h]  
 fistp       qword ptr [esp+10h]