Hello,
On 5/16/12 4:20 PM, Marius Zbihlei wrote:
On 05/16/2012 03:02 PM, Charles Chance wrote:
Currently testing devel version and experiencing the following when
using pua_dialoginfo:
-------------------------------------
Program terminated with signal 11, Segmentation fault.
#0 core_hash (t=0xb3d7e330, type=1024, ps=0xbfcc31c8) at
../../hashes.h:279
279 v=(*p<<24)+(p[1]<<16)+(p[2]<<8)+p[3];
Hello,
Don't know if this is related, but the statement above hides a nasty
bug: p[1] is a char (as for the description), so is signed, shifting
to the left 16 bits is ok, as an integral promotion takes place. The
problem is that if p[1] is negative (-1 is 0xff), then the integral
promotion is signed as well and is complementary of 2 (or whatever the
implementation considers), and the shift will return another value as
expected.
For example :
#include <stdio.h>
int main(){
char b = 0xff;
unsigned h = (b<<16);
printf("%x\n", h);
return 0;
}
will print ffff0000 instead of ff0000 as expected. Haven't calculated
the implication of this related to the bug. An fix would be to cast
p[1] to (unsigned char)
the expression is part of computing the hash code from a string. So it
should not be a cause for crash if it is signed or not. Important is
that for same string, the same hash code is returned.
Cheers,
Daniel
Cheers,
Marius
--
Zbihlei Marius
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1&1 Internet Development srl Tel KA: 754-9152
Str Mircea Eliade 18 Tel RO: +40-31-223-9152
Sect 1, Bucuresti mailto:[email protected]
71295, Romania
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Daniel-Constantin Mierla - http://www.asipto.com
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