On Thu, Apr 20, 2006 at 12:14:48PM +0200, Mathieu Chouquet-Stringer wrote:
> So I guess the strncpy routine on alpha is fscked up or gcc is doing
> something crazy. The function is under arch/alpha/lib/strncpy.S, time to
> learn assembly.
Replying to myself here, i've created the following test program and
redefined strncpy to mystrncpy (I used strncpy.S and stxncpy.S from
arch/alpha/lib):
=============================================================================
#include <stdio.h>
#include <string.h>
#define FOO 50
extern char *mystrncpy(char *dest, const char *src, size_t count);
int main(int argc, char **argv)
{
char src[FOO] = "";
char dest[FOO];
char letter[] = "a";
int i;
for (i = 0; i < FOO - 1; i++) {
size_t beflen, aftlen;
letter[0] = 'a' + i;
strncat(src, letter, FOO);
beflen = strlen(src);
mystrncpy(dest, src, FOO);
aftlen = strlen(dest);
if (beflen != aftlen)
printf("fails for strlen = %ld (copied %ld)\n",
beflen, aftlen);
}
return 0;
}
=============================================================================
And here's the output using gcc version 3.4.4 (Gentoo 3.4.4-r1,
ssp-3.4.4-1.0, pie-8.7.8), note i didn't use flag except -Wall:
fails for strlen = 3 (copied 2)
fails for strlen = 4 (copied 2)
fails for strlen = 5 (copied 2)
fails for strlen = 6 (copied 2)
fails for strlen = 7 (copied 2)
fails for strlen = 11 (copied 10)
fails for strlen = 12 (copied 10)
fails for strlen = 13 (copied 10)
fails for strlen = 14 (copied 10)
fails for strlen = 15 (copied 10)
fails for strlen = 19 (copied 18)
fails for strlen = 20 (copied 18)
fails for strlen = 21 (copied 18)
fails for strlen = 22 (copied 18)
fails for strlen = 23 (copied 18)
fails for strlen = 27 (copied 26)
fails for strlen = 28 (copied 26)
fails for strlen = 29 (copied 26)
fails for strlen = 30 (copied 26)
fails for strlen = 31 (copied 26)
fails for strlen = 35 (copied 34)
fails for strlen = 36 (copied 34)
fails for strlen = 37 (copied 34)
fails for strlen = 38 (copied 34)
fails for strlen = 39 (copied 34)
fails for strlen = 43 (copied 42)
fails for strlen = 44 (copied 42)
fails for strlen = 45 (copied 42)
fails for strlen = 46 (copied 42)
fails for strlen = 47 (copied 42)
So much for this function... I'll look at the assembly to see if I can
understand what's going on: it always copy a multiple of 8 + 2 bytes (as
in 8x + 2).
--
Mathieu Chouquet-Stringer mchouque@xxxxxxx
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