Messages in this thread | | | Date | Thu, 20 Apr 2006 19:11:02 +0200 | From | Mathieu Chouquet-Stringer <> | Subject | strncpy (maybe others) broken on Alpha |
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[ some background here: this started as a kobject_add error from the scsi subsystem, now it appears the strncpy routine on Alpha is broken see http://lkml.org/lkml/fancy/2006/4/19/305 or msgid 20060419213129.GA9148@localhost ]
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@free.fr
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