Date: Fri, 15 Nov 2013 15:47:02 -0500 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Subject: Re: sscanf(3) return value doesn't count %100c assignments On Fri, Nov 15, 2013 at 08:23:42PM +0000, David Wuertele wrote: > Comparing musl-0.9.14 with glibc-2.13, I find sscanf(3) behaves > differently. In Glibc, sscanf() returns the same assignment counts when > using %Nc compared with using %s, but in Mulsl, sscanf returns different > assignment counts. > > For example, take the following two instructions: > > sscanf (string, "%d %s", &number, remainder); > sscanf (string, "%d %100c", &number, remainder); > > If each of these makes two assignments, they should both return 2. > Glibc works this way. But even though with Musl they both make two > assignments, Musl sscanf() returns 2 for the %s and it returns 1 for > the %100c version. musl's sscanf returns 1 because only the %d was matched. %100c requires _exactly_ 100 characters; anything shorter is a matching failure. See C99 18.104.22.168 The fscanf function, paragraph 12: 12 The conversion specifiers and their meanings are: .... c Matches a sequence of characters of exactly the number specified by the field width (1 if no field width is present in the directive). What you're seeing is a known bug in glibc: https://sourceware.org/bugzilla/show_bug.cgi?id=12701 It's an old WONTFIX from the days when Ulrich Drepper was maintainer. Rich
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