Re: bus error in strsep
Stefan Sperling wrote: On Wed, Jul 06, 2005 at 12:10:23PM -0700, Maksim Yevmenkin wrote: Maksim Yevmenkin wrote: char *c = whats:your:name:buddy?; that is not read only copy. you can not write into it. replace it with made type. that should read that is read only copy :) Dark corners of C... So it's my own fault, as usual :) thanks a lot :) Or you can be a bad guy and compile with GCC and -fwritable-strings so that it puts the const string into a read-write section :-). This is an absolutely evil hack, of course. Maxime ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: bus error in strsep
In [EMAIL PROTECTED], Dimitry Andric [EMAIL PROTECTED] typed: On 2005-07-06 at 21:41:00 Stefan Sperling wrote: char *c = whats:your:name:buddy?; made type. that should read that is read only copy :) Dark corners of C... So it's my own fault, as usual :) Actually, this dark corner was enlightened not so long ago. String constants used to be writable for years, until someone decided that it was better not to. :) I think it used to be implementation-dependent. IIRC, the VMS C compiler didn't have writable string constants. I know there was something like that that bit attempts to port Unix programs to VMS. mike -- Mike Meyer [EMAIL PROTECTED] http://www.mired.org/consulting.html Independent Network/Unix/Perforce consultant, email for more information. ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
bus error in strsep
Hello hackers,
I am getting a bus error in my application when I call strsep
and it matches a character. It doesn't matter whether I call
the strsep from my libc or a freshly compiled one, the error
stays the same.
This is my test case:
$ cat strsep.c
#define NULL ((void*)0)
/* copied verbatim from /usr/src/lib/libc/string/strsep.c,
* except for the name change
*/
char *
mystrsep(stringp, delim)
char **stringp;
const char *delim;
{
char *s;
const char *spanp;
int c, sc;
char *tok;
if ((s = *stringp) == NULL)
return (NULL);
for (tok = s;;) {
c = *s++;
spanp = delim;
do {
if ((sc = *spanp++) == c) {
if (c == 0)
s = NULL;
else
s[-1] = 0;
*stringp = s;
return (tok);
}
} while (sc != 0);
}
/* NOTREACHED */
}
int main(int argc, char* argv[])
{
char *c = whats:your:name:buddy?;
(void*)mystrsep(c, :);
}
$ gcc -g -o strsep strsep.c
$ gdb strsep
gnu license
(gdb) run
Starting program: /home/stsp/test/strsep
Program received signal SIGBUS, Bus error.
0x080484f2 in mystrsep (stringp=0xbfbfea34, delim=0x80485e6 :) at strsep.c:26
26 s[-1] = 0;
(gdb) print s[-1]
$1 = 58 ':'
(gdb)
When I single step through mystrsep the program works fine.
I am running FreeBSD-current from 17th June 2005 on an Athlon-XP,
no SMP involved. I can reproduce the error on a dual Celeron box
running FreeBSD-5.4-RELEASE with SMP.
And I also get the same error with similar code using strtok.
Can anyone else reproduce this?
thanks a lot,
--
stefan
http://stsp.in-berlin.de PGP Key: 0xF59D25F0
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Re: bus error in strsep
Stefan,
int main(int argc, char* argv[])
{
char *c = whats:your:name:buddy?;
that is not read only copy. you can not write
into it. replace it with
char *c = strdup(whats:your:name:buddy?);
(void*)mystrsep(c, :);
}
and it should work.
thanks,
max
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Re: bus error in strsep
Maksim Yevmenkin wrote:
Stefan,
int main(int argc, char* argv[])
{
char *c = whats:your:name:buddy?;
that is not read only copy. you can not write into it.
replace it with
made type. that should read that is read only copy :)
char *c = strdup(whats:your:name:buddy?);
(void*)mystrsep(c, :);
}
and it should work.
thanks,
max
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Re: bus error in strsep
On Wed, Jul 06, 2005 at 12:10:23PM -0700, Maksim Yevmenkin wrote: Maksim Yevmenkin wrote: char *c = whats:your:name:buddy?; that is not read only copy. you can not write into it. replace it with made type. that should read that is read only copy :) Dark corners of C... So it's my own fault, as usual :) thanks a lot :) -- stefan http://stsp.in-berlin.de PGP Key: 0xF59D25F0 ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: bus error in strsep
On 2005-07-06 at 21:41:00 Stefan Sperling wrote: char *c = whats:your:name:buddy?; made type. that should read that is read only copy :) Dark corners of C... So it's my own fault, as usual :) Actually, this dark corner was enlightened not so long ago. String constants used to be writable for years, until someone decided that it was better not to. :) Anyway, you can get the old (deprecated!) behaviour by using the -fwritable-strings option to gcc. pgpOjDCRlF0Rw.pgp Description: PGP signature
Re: bus error in strsep
On 2005-07-06 12:08, Maksim Yevmenkin [EMAIL PROTECTED] wrote:
Stefan,
int main(int argc, char* argv[])
{
char *c = whats:your:name:buddy?;
that is not read only copy. you can not write
into it. replace it with
char *c = strdup(whats:your:name:buddy?);
Or the following:
char c[] = whats:your:name:buddy?;
which doesn't require a free() operation when you're done with c[].
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Re: bus error in strsep
int main(int argc, char* argv[])
{
char *c = whats:your:name:buddy?;
that is not read only copy. you can not write
into it. replace it with
char *c = strdup(whats:your:name:buddy?);
Or the following:
char c[] = whats:your:name:buddy?;
which doesn't require a free() operation when you're done with c[].
actually it still will crash :)
beetle% cat 5.c
#include string.h
int
main(int argc, char* argv[])
{
char c[] = whats:your:name:buddy?;
strsep((char **) c, :);
return (0);
}
beetle% gcc -Wall -ggdb 5.c
beetle% ./a.out
Segmentation fault (core dumped)
so something like this
#include string.h
int
main(int argc, char* argv[])
{
char c[] = whats:your:name:buddy?, *s = c;
strsep((char **) s, :);
return (0);
}
will work too.
max
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