Source: gmp Version: 2:6.0.0+dfsg-2 Severity: important Dear Maintainer,
while running the tests for the flint library I am working on packaging, I found that mpz_invert yields a wrong result on a certain set of input values. Essentially, mpz_init(a); mpz_init(b); mpz_init(c); mpz_set_str(a, "11150372594073014712837494417038049594572792", 10) mpz_set_si(b, -1) int x = mpz_invert(c, a, b) yields c = 0 (ok) and x = 1 (not ok). The documentation states:: int mpz_invert (mpz t rop, const mpz t op1, const mpz t op2) Compute the inverse of op1 modulo op2 and put the result in rop. If the inverse exists, the return value is non-zero and rop will satisfy 0 < rop < |op2|. If an inverse doesn’t exist the return value is zero and rop is undefined. The behaviour of this function is undefined when op2 is zero. As 11150372594073014712837494417038049594572792 mod -1 = 0 the inverse does not exist, and the return value should be zero. The fact that !(rop > 0) is actually a clear sign that no inverse exists and rop is thus undefined. Therefore the return value is clearly an error. I have no idea, whether this bug is in the package or in the upstream library. If it concerns upstream, I would be very glad if you forwarded it and set me to CC. Cheers, Benjamin -- System Information: Debian Release: jessie/sid APT prefers unstable APT policy: (600, 'unstable'), (1, 'experimental') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 3.13-1-amd64 (SMP w/2 CPU cores) Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
