[llvm-commits] [llvm] r134554 - in /llvm/trunk: include/llvm/ADT/SmallVector.h unittests/ADT/SmallVectorTest.cpp
Owen Anderson
resistor at mac.com
Wed Jul 6 15:37:00 PDT 2011
Author: resistor
Date: Wed Jul 6 17:36:59 2011
New Revision: 134554
URL: http://llvm.org/viewvc/llvm-project?rev=134554&view=rev
Log:
Fix a subtle issue in SmallVector. The following code did not work as expected:
vec.insert(vec.begin(), vec[3]);
The issue was that vec[3] returns a reference into the vector, which is invalidated when insert() memmove's the elements down to make space. The method needs to specifically detect and handle this case to correctly match std::vector's semantics.
Thanks to Howard Hinnant for clarifying the correct behavior, and explaining how std::vector solves this problem.
Modified:
llvm/trunk/include/llvm/ADT/SmallVector.h
llvm/trunk/unittests/ADT/SmallVectorTest.cpp
Modified: llvm/trunk/include/llvm/ADT/SmallVector.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/SmallVector.h?rev=134554&r1=134553&r2=134554&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/SmallVector.h (original)
+++ llvm/trunk/include/llvm/ADT/SmallVector.h Wed Jul 6 17:36:59 2011
@@ -410,7 +410,14 @@
this->setEnd(this->end()+1);
// Push everything else over.
std::copy_backward(I, this->end()-1, this->end());
- *I = Elt;
+
+ // If we just moved the element we're inserting, be sure to update
+ // the reference.
+ const T *EltPtr = &Elt;
+ if (I <= EltPtr && EltPtr < this->EndX)
+ ++EltPtr;
+
+ *I = *EltPtr;
return I;
}
size_t EltNo = I-this->begin();
Modified: llvm/trunk/unittests/ADT/SmallVectorTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/SmallVectorTest.cpp?rev=134554&r1=134553&r2=134554&view=diff
==============================================================================
--- llvm/trunk/unittests/ADT/SmallVectorTest.cpp (original)
+++ llvm/trunk/unittests/ADT/SmallVectorTest.cpp Wed Jul 6 17:36:59 2011
@@ -35,26 +35,26 @@
Constructable() : value(0) {
++numConstructorCalls;
}
-
+
Constructable(int val) : value(val) {
++numConstructorCalls;
}
-
+
Constructable(const Constructable & src) {
value = src.value;
++numConstructorCalls;
}
-
+
~Constructable() {
++numDestructorCalls;
}
-
+
Constructable & operator=(const Constructable & src) {
value = src.value;
++numAssignmentCalls;
return *this;
}
-
+
int getValue() const {
return abs(value);
}
@@ -64,7 +64,7 @@
numDestructorCalls = 0;
numAssignmentCalls = 0;
}
-
+
static int getNumConstructorCalls() {
return numConstructorCalls;
}
@@ -91,10 +91,10 @@
class SmallVectorTest : public testing::Test {
protected:
typedef SmallVector<Constructable, 4> VectorType;
-
+
VectorType theVector;
VectorType otherVector;
-
+
void SetUp() {
Constructable::reset();
}
@@ -111,7 +111,7 @@
// Assert that theVector contains the specified values, in order.
void assertValuesInOrder(VectorType & v, size_t size, ...) {
EXPECT_EQ(size, v.size());
-
+
va_list ap;
va_start(ap, size);
for (size_t i = 0; i < size; ++i) {
@@ -121,7 +121,7 @@
va_end(ap);
}
-
+
// Generate a sequence of values to initialize the vector.
void makeSequence(VectorType & v, int start, int end) {
for (int i = start; i <= end; ++i) {
@@ -155,18 +155,24 @@
theVector.push_back(Constructable(2));
assertValuesInOrder(theVector, 2u, 1, 2);
+ // Insert at beginning
+ theVector.insert(theVector.begin(), theVector[1]);
+ assertValuesInOrder(theVector, 3u, 2, 1, 2);
+
// Pop one element
theVector.pop_back();
- assertValuesInOrder(theVector, 1u, 1);
+ assertValuesInOrder(theVector, 2u, 2, 1);
- // Pop another element
+ // Pop remaining elements
+ theVector.pop_back();
theVector.pop_back();
assertEmpty(theVector);
-
+
// Check number of constructor calls. Should be 2 for each list element,
- // one for the argument to push_back, and one for the list element itself.
- EXPECT_EQ(4, Constructable::getNumConstructorCalls());
- EXPECT_EQ(4, Constructable::getNumDestructorCalls());
+ // one for the argument to push_back, one for the argument to insert,
+ // and one for the list element itself.
+ EXPECT_EQ(5, Constructable::getNumConstructorCalls());
+ EXPECT_EQ(5, Constructable::getNumDestructorCalls());
}
// Clear test.
@@ -198,7 +204,7 @@
SCOPED_TRACE("ResizeGrowTest");
theVector.resize(2);
-
+
// The extra constructor/destructor calls come from the temporary object used
// to initialize the contents of the resized array (via copy construction).
EXPECT_EQ(3, Constructable::getNumConstructorCalls());
@@ -226,10 +232,10 @@
for (int i = 0; i < 10; ++i) {
EXPECT_EQ(i+1, theVector[i].getValue());
}
-
+
// Now resize back to fixed size.
theVector.resize(1);
-
+
assertValuesInOrder(theVector, 1u, 1);
}
@@ -364,13 +370,13 @@
makeSequence(theVector, 1, 3);
makeSequence(otherVector, 1, 3);
-
+
EXPECT_TRUE(theVector == otherVector);
EXPECT_FALSE(theVector != otherVector);
otherVector.clear();
makeSequence(otherVector, 2, 4);
-
+
EXPECT_FALSE(theVector == otherVector);
EXPECT_TRUE(theVector != otherVector);
}
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