> From: Felix von Leitner [mailto:felix-bugtraq@xxxxxxx] > Sent: Monday, 17 April, 2006 16:04 > > 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); > } > > ... > assert(range_ptrinbuf(buf,(unsigned long)-1,buf+1)==0); > > Imagine my surprise when this assertion failed. As far as the C language is concerned, this isn't a compiler "bug". You've created an invalid pointer in "c+len" (the result neither points within the object that includes the location c points to, nor one past it), which invokes Undefined Behavior (ISO 9899:1990 6.5.6 #8). And you've compared two pointers which do not point within the same object ("c+len>c"), which also invokes Undefined Behavior (6.5.8 #5). The behavior of gcc 4.1 in this case might be infelicitous, but it is not, properly speaking, a bug. -- Michael Wojcik Principal Software Systems Developer, Micro Focus
