Lex: Check for 0 buckets on header map construction

Switch to using `isPowerOf2_32()` to check whether the buckets are a
power of two, and as a side benefit reject loading a header map with no
buckets.  This is a follow-up to r261448.

llvm-svn: 261585

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/unittests/Lex/HeaderMapTest.cpp b/clang/unittests/Lex/HeaderMapTest.cpp
index e8921709604..ad0579a236e 100644
--- a/clang/unittests/Lex/HeaderMapTest.cpp
+++ b/clang/unittests/Lex/HeaderMapTest.cpp
@@ -143,6 +143,15 @@ TEST(HeaderMapTest, checkHeader3Buckets) {
   ASSERT_FALSE(HeaderMapImpl::checkHeader(*File.getBuffer(), NeedsSwap));
 }
 
+TEST(HeaderMapTest, checkHeader0Buckets) {
+  // Create with 1 bucket to avoid 0-sized arrays.
+  MapFile<1, 1> File;
+  File.init();
+  File.Header.NumBuckets = 0;
+  bool NeedsSwap;
+  ASSERT_FALSE(HeaderMapImpl::checkHeader(*File.getBuffer(), NeedsSwap));
+}
+
 TEST(HeaderMapTest, checkHeaderNotEnoughBuckets) {
   MapFile<1, 1> File;
   File.init();