concatLists: Don't pass NULL pointers to memcpy.

This is UB, even if the size is 0. See #1976.

Fixes #1976.
This commit is contained in:
Shea Levy 2018-03-14 23:44:02 -04:00
parent 55aa622fb1
commit e2088febf3
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@ -1316,6 +1316,7 @@ void EvalState::concatLists(Value & v, unsigned int nrLists, Value * * lists, co
auto out = v.listElems();
for (unsigned int n = 0, pos = 0; n < nrLists; ++n) {
unsigned int l = lists[n]->listSize();
if (l)
memcpy(out + pos, lists[n]->listElems(), l * sizeof(Value *));
pos += l;
}