Bug#289264: libc6: scanf() wrong results

[Paul Vojta <vojta@Math.Berkeley.EDU>]

Package: libc6
Version: 2.3.2.ds1-20
Severity: normal

scanf() sometimes produces erroneous results (it reads part of the next
line when it shouldn't).  See the attached program (which runs correctly
on Solaris 9).


-- System Information:
Debian Release: 3.1
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.4.27
Locale: LANG=C, LC_CTYPE=en_US.ISO-8859-1 (charmap=ISO-8859-1)

Versions of packages libc6 depends on:
ii  libdb1-compat                 2.1.3-7    The Berkeley database routines [gl

-- no debconf information

#include <stdio.h>

/*
 * This program exhibits a bug with scanf() processing.
 *
 * Compile with:
 *	gcc -Wall -o scanftest scanftest.c
 *
 * Run with:
 *	./scanftest < data
 * or
 *	./scanftest < data | diff data -
 *
 * The output should coincide with the input, but it doesn't.
 */

int
main()
{
	int	n;
	char	name[3];
	int	hw[17];
	int	i;

	n = 0;
	for (;;) {
	    double	h[17];
	    double	junk;

	    i = scanf("%c%c%c "
	      "%lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf "
	      "%lf %lf %lf %lf\n",
	      &name[0], &name[1], &name[2],
	      &h[0], &h[1], &h[2], &h[3], &h[4], &h[5], &h[6], &h[7], &h[8],
	      &h[9], &h[10], &h[11], &h[12], &h[13], &h[14], &h[15], &h[16],
	      &junk);

	    if (i == EOF) break;
	    if (i != 20) {
		fprintf(stderr, "At line %d, got %d values instead of 20.\n",
		  n + 1, i);
		return 1;
	    }

	    for (i = 0; i < 17; ++i)
		hw[i] = h[i];

	    printf("%c%c%c", name[0], name[1], name[2]);
	    for (i = 0; i < 16; ++i)
		printf(" %2d", hw[i]);
	    printf("%2d\n", hw[16]);

	    ++n;
	}

	return 0;
}

Abc  0  1  2  3  4  5  6  7  8  9 10 11 12 13 23 34 0
Bcd  1  2  3  4  5  6  7  8  9 10 11 12 13 14 24 35 0
Cde  2  3  4  5  6  7  8  9 10 11 12 13 14 15 25 36 0
Def  3  4  5  6  7  8  9 10 11 12 13 14 15 16 26 37 0
Efg  4  5  6  7  8  9 10 11 12 13 14 15 16 17 27 38 0
Fgh  5  6  7  8  9 10 11 12 13 14 15 16 17 18 28 39 0
Ghi  6  7  8  9 10 11 12 13 14 15 16 17 18 19 29 40 0
Hij  7  8  9 10 11 12 13 14 15 16 17 18 19 20 30 41 0
Ijk  8  9 10 11 12 13 14 15 16 17 18 19 20 21 31 42 0
Jkl  9 10 11 12 13 14 15 16 17 18 19 20 21 22 32 43 0
Klm 10 11 12 13 14 15 16 17 18 19 20 21 22 23 33 44 0
Lmn 11 12 13 14 15 16 17 18 19 20 21 22 23 24 34 45 0
Mno 12 13 14 15 16 17 18 19 20 21 22 23 24 25 35 46 0
Nop 13 14 15 16 17 18 19 20 21 22 23 24 25 26 36 47 0
Opq 14 15 16 17 18 19 20 21 22 23 24 25 26 27 37 48 0
Pqr 15 16 17 18 19 20 21 22 23 24 25 26 27 28 38 49 0