I'm using the PellesC C compiler. Sometimes my code randomly stops working. A particular statement can trigger it. For example, I multiplied a variable by sin(c) (c is a double) and my code seemed to just finish execution with no result. Sometimes it freezes, sometimes it appears to just return, but I can always fix it by removing the offending statement or disabling compiler optimizations, specifically "maximize speed" or "maximize speed more". The freezing will also go away nearly 100% of the time if I add a printf statement somewhere near the point at which it crashes. I've never found anything to suggest that I am accessing memory improperly, I'm fairly sure its a compiler issue. I was wondering if anybody could shed some light on this. Is it possible that I am, in fact, doing something wrong? Or is this a known issue with the Pelles C compiler?
Edit:
Changing
canvas->pixels[(y*canvas->pitch)+(x*canvas->Bpp)+2]=(unsigned char)(255.0*dtempA*(1-sin(c)));
canvas->pixels[(y*canvas->pitch)+(x*canvas->Bpp)+1]=(unsigned char)(255.0*dtempA*(1+cos(c)));
canvas->pixels[(y*canvas->pitch)+(x*canvas->Bpp)]=(unsigned char)(255.0*dtempA*(1+sin(c)));
to (difference at the end of the last line)
canvas->pixels[(y*canvas->pitch)+(x*canvas->Bpp)+2]=(unsigned char)(255.0*dtempA*(1-sin(c)));
canvas->pixels[(y*canvas->pitch)+(x*canvas->Bpp)+1]=(unsigned char)(255.0*dtempA*(1+cos(c)));
canvas->pixels[(y*canvas->pitch)+(x*canvas->Bpp)]=(unsigned char)(255.0*dtempA*(1+1));
makes it work.
You're probably accidentally using undefined behavior somewhere, and changing random instructions in the program is breaking the very fragile alignment of the code on the stack that happens to make the program work.