* memmem() - is it correct?
@ 2014-04-09 10:08 u-igbb
2014-04-09 10:19 ` Timo Teras
0 siblings, 1 reply; 6+ messages in thread
From: u-igbb @ 2014-04-09 10:08 UTC (permalink / raw)
To: musl
A test case adapted from elsewhere:
----
#include <string.h>
main(){
const char *haystack = "abcde";
return(!memmem(haystack, 4, "cde", 3));
}
----
returns 1 (as I would expect it to) if linked against uclibc
returns 0 if linked against musl
(on ia32)
Any comments?
Rune
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: memmem() - is it correct? 2014-04-09 10:08 memmem() - is it correct? u-igbb @ 2014-04-09 10:19 ` Timo Teras [not found] ` <20140409104925.GE21662@example.net> 0 siblings, 1 reply; 6+ messages in thread From: Timo Teras @ 2014-04-09 10:19 UTC (permalink / raw) To: musl; +Cc: u-igbb On Wed, 9 Apr 2014 12:08:40 +0200 u-igbb@aetey.se wrote: > A test case adapted from elsewhere: > ---- > #include <string.h> > > main(){ > const char *haystack = "abcde"; > return(!memmem(haystack, 4, "cde", 3)); > } > ---- > > returns 1 (as I would expect it to) if linked against uclibc > returns 0 if linked against musl > (on ia32) > > Any comments? musl looks correct to me. "abcde" is five bytes. You test for 4 bytes so it's infact searching from haystack equivalent of "abcd". I'd say uclibc is off-by-one, and broken. - Timo ^ permalink raw reply [flat|nested] 6+ messages in thread
[parent not found: <20140409104925.GE21662@example.net>]
* Re: memmem() - is it correct? [not found] ` <20140409104925.GE21662@example.net> @ 2014-04-09 12:51 ` Timo Teras 2014-04-09 12:54 ` Timo Teras 0 siblings, 1 reply; 6+ messages in thread From: Timo Teras @ 2014-04-09 12:51 UTC (permalink / raw) To: u-igbb; +Cc: musl On Wed, 9 Apr 2014 12:49:25 +0200 u-igbb@aetey.se wrote: > On Wed, Apr 09, 2014 at 01:19:03PM +0300, Timo Teras wrote: > > > const char *haystack = "abcde"; > > > return(!memmem(haystack, 4, "cde", 3)); > > > > returns 1 (as I would expect it to) if linked against uclibc > > > returns 0 if linked against musl > > > (on ia32) > > I guess you misinterpreted the test code, there is a '!' which > transforms a returned pointer (success) to 0 exit status in main() > and vice versa. Right. Should have read it more carefully. Yes, looks like musl bug. Perhaps something like the following is in place: diff --git a/src/string/memmem.c b/src/string/memmem.c index 5211d75..0594fea 100644 --- a/src/string/memmem.c +++ b/src/string/memmem.c @@ -138,7 +138,9 @@ void *memmem(const void *h0, size_t k, const void *n0, size_t l) /* Use faster algorithms for short needles */ h = memchr(h0, *n, k); - if (!h || l==1) return (void *)h; + if (!h) return 0; + if (l==1) return (void *)h; + k -= h - h0; if (l==2) return twobyte_memmem(h, k, n); if (l==3) return threebyte_memmem(h, k, n); if (l==4) return fourbyte_memmem(h, k, n); ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: memmem() - is it correct? 2014-04-09 12:51 ` Timo Teras @ 2014-04-09 12:54 ` Timo Teras 2014-04-10 1:15 ` Rich Felker 0 siblings, 1 reply; 6+ messages in thread From: Timo Teras @ 2014-04-09 12:54 UTC (permalink / raw) To: u-igbb; +Cc: musl On Wed, 9 Apr 2014 15:51:16 +0300 Timo Teras <timo.teras@iki.fi> wrote: > On Wed, 9 Apr 2014 12:49:25 +0200 > u-igbb@aetey.se wrote: > > > On Wed, Apr 09, 2014 at 01:19:03PM +0300, Timo Teras wrote: > > > > const char *haystack = "abcde"; > > > > return(!memmem(haystack, 4, "cde", 3)); > > > > > > returns 1 (as I would expect it to) if linked against uclibc > > > > returns 0 if linked against musl > > > > (on ia32) > > > > I guess you misinterpreted the test code, there is a '!' which > > transforms a returned pointer (success) to 0 exit status in main() > > and vice versa. > > Right. Should have read it more carefully. Yes, looks like musl bug. > > Perhaps something like the following is in place: Wrong patch version. Should be as simple as: diff --git a/src/string/memmem.c b/src/string/memmem.c index 5211d75..1173020 100644 --- a/src/string/memmem.c +++ b/src/string/memmem.c @@ -139,6 +139,7 @@ void *memmem(const void *h0, size_t k, const void *n0, size_t l) /* Use faster algorithms for short needles */ h = memchr(h0, *n, k); if (!h || l==1) return (void *)h; + k -= h - (const unsigned char*)h0; if (l==2) return twobyte_memmem(h, k, n); if (l==3) return threebyte_memmem(h, k, n); if (l==4) return fourbyte_memmem(h, k, n); ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: memmem() - is it correct? 2014-04-09 12:54 ` Timo Teras @ 2014-04-10 1:15 ` Rich Felker 0 siblings, 0 replies; 6+ messages in thread From: Rich Felker @ 2014-04-10 1:15 UTC (permalink / raw) To: musl; +Cc: u-igbb On Wed, Apr 09, 2014 at 03:54:03PM +0300, Timo Teras wrote: > On Wed, 9 Apr 2014 15:51:16 +0300 > Timo Teras <timo.teras@iki.fi> wrote: > > > On Wed, 9 Apr 2014 12:49:25 +0200 > > u-igbb@aetey.se wrote: > > > > > On Wed, Apr 09, 2014 at 01:19:03PM +0300, Timo Teras wrote: > > > > > const char *haystack = "abcde"; > > > > > return(!memmem(haystack, 4, "cde", 3)); > > > > > > > > returns 1 (as I would expect it to) if linked against uclibc > > > > > returns 0 if linked against musl > > > > > (on ia32) > > > > > > I guess you misinterpreted the test code, there is a '!' which > > > transforms a returned pointer (success) to 0 exit status in main() > > > and vice versa. > > > > Right. Should have read it more carefully. Yes, looks like musl bug. > > > > Perhaps something like the following is in place: > > Wrong patch version. Should be as simple as: > > diff --git a/src/string/memmem.c b/src/string/memmem.c > index 5211d75..1173020 100644 > --- a/src/string/memmem.c > +++ b/src/string/memmem.c > @@ -139,6 +139,7 @@ void *memmem(const void *h0, size_t k, const void > *n0, size_t l) /* Use faster algorithms for short needles */ > h = memchr(h0, *n, k); > if (!h || l==1) return (void *)h; > + k -= h - (const unsigned char*)h0; > if (l==2) return twobyte_memmem(h, k, n); > if (l==3) return threebyte_memmem(h, k, n); > if (l==4) return fourbyte_memmem(h, k, n); Thanks! Committed. Rich ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: memmem() - is it correct? @ 2014-04-09 12:14 u-igbb 0 siblings, 0 replies; 6+ messages in thread From: u-igbb @ 2014-04-09 12:14 UTC (permalink / raw) To: musl On Wed, Apr 09, 2014 at 01:19:03PM +0300, Timo Teras wrote: > > const char *haystack = "abcde"; > > return(!memmem(haystack, 4, "cde", 3)); > > returns 1 (as I would expect it to) if linked against uclibc > > returns 0 if linked against musl > > (on ia32) > musl looks correct to me. "abcde" is five bytes. You test for 4 bytes I am testing for 3 bytes "cde" inside 4 bytes "abcd", this should not be successful. > so it's infact searching from haystack equivalent of "abcd". Exactly. It does _not_ contain "cde". This should return NULL from the memmem() and hence 1 from main(). > I'd say uclibc is off-by-one, and broken. I guess you misinterpreted the test code, there is a '!' which transforms a returned pointer (success) to 0 exit status in main() and vice versa. Rune ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2014-04-10 1:15 UTC | newest]
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2014-04-09 10:08 memmem() - is it correct? u-igbb
2014-04-09 10:19 ` Timo Teras
[not found] ` <20140409104925.GE21662@example.net>
2014-04-09 12:51 ` Timo Teras
2014-04-09 12:54 ` Timo Teras
2014-04-10 1:15 ` Rich Felker
2014-04-09 12:14 u-igbb
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