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Fix SIGFPE from integer overflow during division

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On some architectures (like x86_64 or i686, but not ARM for example)
overflow during integer division causes a crash due to SIGFPE.
Reproduces on a 64-bit system with:

    nix-instantiate --eval -E '(-9223372036854775807 - 1) / -1'

The only way this can happen is when the smallest possible integer is
divided by -1, so just special-case that.
This commit is contained in:
Tuomas Tynkkynen 2016-10-26 18:09:01 +03:00
parent 5c0bd51d49
commit f0fc3dd88b
1 changed files with 9 additions and 3 deletions
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12
src/libexpr/primops.cc
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@ -1516,10 +1516,16 @@ static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value &
NixFloat f2 = state.forceFloat(*args[1], pos);
if (f2 == 0) throw EvalError(format("division by zero, at %1%") % pos);
if (args[0]->type == tFloat || args[1]->type == tFloat)
if (args[0]->type == tFloat || args[1]->type == tFloat) {
mkFloat(v, state.forceFloat(*args[0], pos) / state.forceFloat(*args[1], pos));
else
mkInt(v, state.forceInt(*args[0], pos) / state.forceInt(*args[1], pos));
} else {
NixInt i1 = state.forceInt(*args[0], pos);
NixInt i2 = state.forceInt(*args[1], pos);
/* Avoid division overflow as it might raise SIGFPE. */
if (i1 == std::numeric_limits<NixInt>::min() && i2 == -1)
throw EvalError(format("overflow in integer division, at %1%") % pos);
mkInt(v, i1 / i2);
}
}