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Fix a segfault in genericClosure 

It kept temporary data in STL containers that were not scanned by
Boehm GC, so Nix programs using genericClosure could randomly crash if
the garbage collector kicked in at a bad time.

Also make it a bit more efficient by copying points to values rather
than values.
This commit is contained in:
Eelco Dolstra 2013-10-28 18:50:58 +01:00
parent 6123144933
commit dec2f19502
1 changed files with 25 additions and 16 deletions
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41
src/libexpr/primops.cc
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@ -158,24 +158,31 @@ static void prim_isBool(EvalState & state, Value * * args, Value & v)
struct CompareValues
{
bool operator () (const Value & v1, const Value & v2) const
bool operator () (const Value * v1, const Value * v2) const
{
if (v1.type != v2.type)
if (v1->type != v2->type)
throw EvalError("cannot compare values of different types");
switch (v1.type) {
switch (v1->type) {
case tInt:
return v1.integer < v2.integer;
return v1->integer < v2->integer;
case tString:
return strcmp(v1.string.s, v2.string.s) < 0;
return strcmp(v1->string.s, v2->string.s) < 0;
case tPath:
return strcmp(v1.path, v2.path) < 0;
return strcmp(v1->path, v2->path) < 0;
default:
throw EvalError(format("cannot compare %1% with %2%") % showType(v1) % showType(v2));
throw EvalError(format("cannot compare %1% with %2%") % showType(*v1) % showType(*v2));
}
}
};
#if HAVE_BOEHMGC
typedef list<Value *, gc_allocator<Value *> > ValueVector;
#else
typedef vector<Value *> ValueVector;
#endif
static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
{
startNest(nest, lvlDebug, "finding dependencies");
@ -189,7 +196,7 @@ static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
throw EvalError("attribute `startSet' required");
state.forceList(*startSet->value);
list<Value *> workSet;
ValueVector workSet;
for (unsigned int n = 0; n < startSet->value->list.length; ++n)
workSet.push_back(startSet->value->list.elems[n]);
@ -203,8 +210,10 @@ static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
/* Construct the closure by applying the operator to element of
`workSet', adding the result to `workSet', continuing until
no new elements are found. */
list<Value> res;
set<Value, CompareValues> doneKeys; // !!! use Value *?
ValueVector res;
// `doneKeys' doesn't need to be a GC root, because its values are
// reachable from res.
set<Value *, CompareValues> doneKeys;
while (!workSet.empty()) {
Value * e = *(workSet.begin());
workSet.pop_front();
@ -217,9 +226,9 @@ static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
throw EvalError("attribute `key' required");
state.forceValue(*key->value);
if (doneKeys.find(*key->value) != doneKeys.end()) continue;
doneKeys.insert(*key->value);
res.push_back(*e);
if (doneKeys.find(key->value) != doneKeys.end()) continue;
doneKeys.insert(key->value);
res.push_back(e);
/* Call the `operator' function with `e' as argument. */
Value call;
@ -236,8 +245,8 @@ static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
/* Create the result list. */
state.mkList(v, res.size());
unsigned int n = 0;
foreach (list<Value>::iterator, i, res)
*(v.list.elems[n++] = state.allocValue()) = *i;
foreach (ValueVector::iterator, i, res)
v.list.elems[n++] = *i;
}
@ -1056,7 +1065,7 @@ static void prim_lessThan(EvalState & state, Value * * args, Value & v)
state.forceValue(*args[0]);
state.forceValue(*args[1]);
CompareValues comp;
mkBool(v, comp(*args[0], *args[1]));
mkBool(v, comp(args[0], args[1]));
}