* Felix von Leitner: > static inline int range_ptrinbuf(const void* buf,unsigned long len,const void* ptr) { > register const char* c=(const char*)buf; /* no pointer arithmetic on void* */ > return (c && c+len>c && (const char*)ptr-c<len); > } It seems that the problem is that c + len > c is equivalent to len != 0. Either c + len is within the same object c points to, and it's value is larger than c (provided that len is not zero), or c + len is undefined (because it's not the same object). In the latter case, the outcome is not specified by the C standard (or the GCC documentation), so it's permissible to choose len != 0 as the value, too. I wouldn't rule out a compiler bug in this area, but the test case is invalid.