Re: [musl] Behaviour of strverscmp(3)

[Rich Felker <dalias@libc.org>]

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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

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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. */