Resize vector have does not work correctly

[dorooleg]

Summary

When resize is done in smaller side need to move the pointer end

Vector<int> v;
v.PushBack(1);
v.PushBack(2);
v.Size(); // 1
v.Resize(1);
v.Size() // 2 but should be 1

Patch by Oleg Doronin

[vitalybuka]

could you please extend compiler-rt/lib/sanitizer_common/tests/sanitizer_vector_test.cc ?

[kcc]

Hm... interesting. how did you find it? what does this affect now?
I think it should be fixed in Resize().
Also, please add a test here: lib/sanitizer_common/tests/sanitizer_vector_test.cc

[dorooleg]

@vitalybuka, @kcc thanks for the comments. ResizeReduction test was added into compiler-rt/lib/sanitizer_common/tests/sanitizer_vector_test.cc
As recommended by @kcc the changes are transferred to the method Resize
An error was found while attempting to use Vector in my own changes. How I see this error does not affect the current logic, so as to Resize is used to increase the size of the Vector

[kcc]

LGTM, thanks!
Vitaly, please land.
This doesn't affect this review, but next time please upload patches with full context (the 'arc' tool is pretty good at it).

[vitalybuka]

Update description

compiler-rt/trunk/lib/sanitizer_common/sanitizer_vector.h

public:
   }
 
   void Resize(uptr size) {
     if (size == 0) {
       end_ = begin_;
       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++)
         internal_memset(&begin_[i], 0, sizeof(begin_[i]));
     }
   }
 
  private:

compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_vector_test.cc

for (int i = 0; i < 1000; i++) {
     EXPECT_EQ(v.Size(), i + 1u);
     EXPECT_EQ(v[i], i);
   }
   for (int i = 0; i < 1000; i++) {
     EXPECT_EQ(v[i], i);
   }
 }
 
+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