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Message-ID: <20221108032509.GH29905@brightrain.aerifal.cx> Date: Mon, 7 Nov 2022 22:25:09 -0500 From: Rich Felker <dalias@...c.org> To: Dmitry Bogatov <oht-tfnfy#tah.bet#i1@...tion.cc> Cc: bug-gsasl@....org, musl@...ts.openwall.com Subject: Re: Behaviour of strverscmp(3) On Mon, Nov 07, 2022 at 10:08:25PM -0500, Rich Felker wrote: > On Sun, Nov 06, 2022 at 06:39:04PM -0500, Rich Felker wrote: > > On Sun, Nov 06, 2022 at 06:18:22PM -0500, Dmitry Bogatov wrote: > > > Hello. > > > > > > While trying to building gsasl statically with musl library as part of > > > Nixpkgs distribution, I noticed that test built from tests/version.c > > > fails when built with musl library. After a bit of troubleshooting, I > > > can pinpoint the reason -- different behaviour of "strverscmp" from > > > glibc and musl. > > > > > > Example code: > > > > > > #include <string.h> > > > #include <stdio.h> > > > > > > int main() > > > { > > > int value = strverscmp("UNKNOWN", "2.2.0"); > > > printf("%d\n", value); > > > return 0; > > > } > > > > > > Under glibc value "35" is printed (positive), under musl value "-1" is > > > printed (negative). Not sure what is the correct solution for the > > > issue, so I cross-post into two lists. > > > > > > For now I plan to patch-out this particular test. Thank you. > > > > It looks like we're neglecting to honor the exception case to "longer > > digit sequence is greater" when one of the sequences is degenerate (no > > digits). > > I think the attached patch fixes it in the most non-invasive way > that's most clear in avoiding other unwanted side effects. It > basically says "only apply the longest-digit-sequence" rule if there > is a common nonzero length [[:digit:]]+ match (dp is the position > where digit sequence starts, j is the test position). > > I think this code should be reviewed for additional bugs though. > > Rich > diff --git a/src/string/strverscmp.c b/src/string/strverscmp.c > index 4daf276d..9e35422a 100644 > --- a/src/string/strverscmp.c > +++ b/src/string/strverscmp.c > @@ -22,8 +22,8 @@ int strverscmp(const char *l0, const char *r0) > /* If we're not looking at a digit sequence that began > * with a zero, longest digit string is greater. */ > for (j=i; isdigit(l[j]); j++) > - if (!isdigit(r[j])) return 1; > - if (isdigit(r[j])) return -1; > + if (dp<j && !isdigit(r[j])) return 1; > + if (dp<j && isdigit(r[j])) return -1; > } else if (z && dp<i && (isdigit(l[i]) || isdigit(r[i]))) { > /* Otherwise, if common prefix of digit sequence is > * all zeros, digits order less than non-digits. */ An alternate way to do this might be changing the condition for the if block: - if (l[dp]!='0' && r[dp]!='0') { + if (l[dp]-'1'<9U && r[dp]-'1'<9U) { That is, only doing the longest-digit-sequence logic at all if both l and r have a nonzero digit at dp. This is probably more efficient. Rich
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