From 361e1716729a34d19aa8bace4e6be44c295c3e1d Mon Sep 17 00:00:00 2001 From: Peter Stephenson Date: Thu, 6 Sep 2012 18:22:30 +0000 Subject: 30656: prevent SIGFPE in division by -1 by multiplying instead --- Src/math.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) (limited to 'Src/math.c') diff --git a/Src/math.c b/Src/math.c index cca521098..c7d384019 100644 --- a/Src/math.c +++ b/Src/math.c @@ -1053,14 +1053,34 @@ op(int what) return; if (c.type == MN_FLOAT) c.u.d = a.u.d / b.u.d; - else - c.u.l = a.u.l / b.u.l; + else { + /* + * Avoid exception when dividing the smallest + * negative integer by -1. Always treat it the + * same as multiplication. This still doesn't give + * numerically the right answer in two's complement, + * but treating both these in the same way seems + * reasonable. + */ + if (b.u.l == -1) + c.u.l = - a.u.l; + else + c.u.l = a.u.l / b.u.l; + } break; case MOD: case MODEQ: if (!notzero(b)) return; - c.u.l = a.u.l % b.u.l; + /* + * Avoid exception as above. + * Any integer mod -1 is the same as any integer mod 1 + * i.e. zero. + */ + if (b.u.l == -1) + c.u.l = 0; + else + c.u.l = a.u.l % b.u.l; break; case PLUS: case PLUSEQ: -- cgit 1.4.1