[sanitizer] Fix __sanitizer::Vector::Resize vector

Implemented downsizing

Patch by Oleg Doronin

Reviewers: kcc, vitalybuka

Reviewed By: kcc, vitalybuka

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45605

llvm-svn: 330049

2 files changed, 13 insertions, 0 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_vector.h b/compiler-rt/lib/sanitizer_common/sanitizer_vector.h
index 25cfeed35f2..0632ccce262 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_vector.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_vector.h
@@ -82,6 +82,10 @@ class Vector {
       return;
     }
     uptr old_size = Size();
+    if (size <= old_size) {
+      end_ = begin_ + size;
+      return;
+    }
     EnsureSize(size);
     if (old_size < size) {
       for (uptr i = old_size; i < size; i++)
diff --git a/compiler-rt/lib/sanitizer_common/tests/sanitizer_vector_test.cc b/compiler-rt/lib/sanitizer_common/tests/sanitizer_vector_test.cc
index bdcab7dd7f8..59fbf39685b 100644
--- a/compiler-rt/lib/sanitizer_common/tests/sanitizer_vector_test.cc
+++ b/compiler-rt/lib/sanitizer_common/tests/sanitizer_vector_test.cc
@@ -39,4 +39,13 @@ TEST(Vector, Stride) {
   }
 }
 
+TEST(Vector, ResizeReduction) {
+  Vector<int> v;
+  v.PushBack(0);
+  v.PushBack(0);
+  EXPECT_EQ(v.Size(), 2u);
+  v.Resize(1);
+  EXPECT_EQ(v.Size(), 1u);
+}
+
 }  // namespace __sanitizer