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30656: prevent SIGFPE in division by -1 by multiplying instead

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Peter Stephenson 2012-09-06 18:22:30 +00:00
parent 1f5ef83f0f
commit 361e171672
2 changed files with 29 additions and 4 deletions
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7
ChangeLog
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@ -1,3 +1,8 @@
2012-09-06 Peter Stephenson <p.w.stephenson@ntlworld.com>
* 30656: Src/math.c: treat dividing by -1 the same as
multiplying by it to get around SIGFPE.
2012-09-05 Peter Stephenson <pws@csr.com> 2012-09-05 Peter Stephenson <pws@csr.com>
* Jun T.: 30658: Completion/Unix/Command/_uniq: more options. * Jun T.: 30658: Completion/Unix/Command/_uniq: more options.
@ -137,5 +142,5 @@
***************************************************** *****************************************************
* This is used by the shell to define $ZSH_PATCHLEVEL * This is used by the shell to define $ZSH_PATCHLEVEL
* $Revision: 1.5715 $ * $Revision: 1.5716 $
***************************************************** *****************************************************

26
Src/math.c
View file

@ -1053,14 +1053,34 @@ op(int what)
return; return;
if (c.type == MN_FLOAT) if (c.type == MN_FLOAT)
c.u.d = a.u.d / b.u.d; c.u.d = a.u.d / b.u.d;
else else {
c.u.l = a.u.l / b.u.l; /*
* 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; break;
case MOD: case MOD:
case MODEQ: case MODEQ:
if (!notzero(b)) if (!notzero(b))
return; 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; break;
case PLUS: case PLUS:
case PLUSEQ: case PLUSEQ: