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Fix PR13148, an inf-loop in StringMap.

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StringMap suffered from the same bug as DenseMap: when you explicitly
construct it with a small number of buckets, you can arrange for the
tombstone-based growth path to be followed when the number of buckets
was less than '8'. In that case, even with a full map, it would compare
'0' as not less than '0', and refuse to grow the table, leading to
inf-loops trying to find an empty bucket on the next insertion. The fix
is very simple: use '<=' as the comparison. The same fix was applied to
DenseMap as well during its recent refactoring.

Thanks to Alex Bolz for the great report and test case. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158725 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2012-06-19 17:40:35 +00:00
parent 0fb9b9a46a
commit 2a79116940
2 changed files with 23 additions and 1 deletions
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2
lib/Support/StringMap.cpp
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@ -189,7 +189,7 @@ void StringMapImpl::RehashTable() {
// grow/rehash the table.
if (NumItems*4 > NumBuckets*3) {
NewSize = NumBuckets*2;
} else if (NumBuckets-(NumItems+NumTombstones) < NumBuckets/8) {
} else if (NumBuckets-(NumItems+NumTombstones) <= NumBuckets/8) {
NewSize = NumBuckets;
} else {
return;

22
unittests/ADT/StringMapTest.cpp
View File

@ -134,6 +134,28 @@ TEST_F(StringMapTest, InsertAndEraseTest) {
assertSingleItemMap();
}
TEST_F(StringMapTest, SmallFullMapTest) {
// StringMap has a tricky corner case when the map is small (<8 buckets) and
// it fills up through a balanced pattern of inserts and erases. This can
// lead to inf-loops in some cases (PR13148) so we test it explicitly here.
llvm::StringMap<int> Map(2);
Map["eins"] = 1;
Map["zwei"] = 2;
Map["drei"] = 3;
Map.erase("drei");
Map.erase("eins");
Map["veir"] = 4;
Map["funf"] = 5;
EXPECT_EQ(3u, Map.size());
EXPECT_EQ(0, Map.lookup("eins"));
EXPECT_EQ(2, Map.lookup("zwei"));
EXPECT_EQ(0, Map.lookup("drei"));
EXPECT_EQ(4, Map.lookup("veir"));
EXPECT_EQ(5, Map.lookup("funf"));
}
// A more complex iteration test.
TEST_F(StringMapTest, IterationTest) {
bool visited[100];