From: David Wuertele <dave+gmane@wuertele.com>
To: musl@lists.openwall.com
Subject: sscanf(3) return value doesn't count %100c assignments
Date: Fri, 15 Nov 2013 20:23:42 +0000 (UTC) [thread overview]
Message-ID: <loom.20131115T212022-997@post.gmane.org> (raw)
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.
Here is a test program:
#include <stdio.h>
#include <strings.h>
int main ()
{
int number = 0;
char *string = "1234 five six seven";
char remainder[100];
bzero (remainder, sizeof(remainder));
int args = sscanf (string, "%d %s", &number, remainder);
fprintf (stderr,
"format=%%s string=\"%s\" args=%d number=%d remainder=%s\n",
string, args, number, remainder);
args = sscanf (string, "%d %100c", &number, remainder);
fprintf (stderr,
"format=%%100c string=\"%s\" args=%d number=%d remainder=%s\n",
string, args, number, remainder);
return 0;
}
Here is how I compile them:
arm-tegra452-linux-gnueabi-gcc --static test.c -o test-glibc
arm-linux-musleabishf-gcc -static test.c -o test-musl
Here is what I see when I execute them:
# ./test-musl
format=%s string="1234 five six" args=2 number=1234 remainder=five
format=%100c string="1234 five six" args=1 number=1234 remainder=five six
# ./test-glibc
format=%s string="1234 five six" args=2 number=1234 remainder=five
format=%100c string="1234 five six" args=2 number=1234 remainder=five six
This seems like a bug to me. I tried to read through
musl-0.9.14/src/stdio/vfscanf.c to troubleshoot this, but I couldn't find the
source of the difference. Can anyone give me pointers to build a musl-libc
that has a sscanf() that is compatible with glibc's sscanf()?
Thanks,
Dave
next reply other threads:[~2013-11-15 20:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-15 20:23 David Wuertele [this message]
2013-11-15 20:47 ` Rich Felker
2013-11-15 21:17 ` David Wuertele
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