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Fix a segfault in genericClosure

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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
View file

@ -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]));
}