BugTraq
gcc 4.1 bug miscompiles pointer range checks, may place you at risk Apr 17 2006 08:03PM
Felix von Leitner (felix-bugtraq fefe de) (6 replies)
Re: gcc 4.1 bug miscompiles pointer range checks, may place you at risk Apr 18 2006 07:16PM
Florian Weimer (fw deneb enyo de)
* 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.

[ reply ]
Re: gcc 4.1 bug miscompiles pointer range checks, may place you at risk Apr 18 2006 09:21AM
Gabor Gombas (gombasg sztaki hu)
Re: gcc 4.1 bug miscompiles pointer range checks, may place you at risk Apr 18 2006 07:45AM
Alexander Klimov (alserkli inbox ru)
Re: gcc 4.1 bug miscompiles pointer range checks, may place you at risk Apr 18 2006 12:15AM
Nate Eldredge (nge cs hmc edu)
Re: gcc 4.1 bug miscompiles pointer range checks, may place you at risk Apr 17 2006 11:57PM
Michael Chamberlain (michael chamberlain net au)
Re: gcc 4.1 bug miscompiles pointer range checks, may place you at risk Apr 17 2006 10:26PM
Forrest J. Cavalier III (mibsoft mibsoftware com)


 

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