I've got a class definition similar to the following:
class UUID
{
public:
// Using implicit copy assignment operator
private:
unsigned char buffer[16];
};
I've just had a unit test fail on me that was verifying that copy assignment worked properly. To my surprise, one byte in the middle of the buffer[] array was copied incorrectly.
My understanding is that the default copy assignment operator performs memberwise copy, and that for array members (not pointer-to-array members) that entails elementwise copy of the array. Am I mistaken?
My gut feeling here is that I've been bitten by a dangling pointer somewhere that has stomped on the middle of my array. But, I'm seeing this repeatably when, e.g. I copy a vector of these objects into another vector.
Anybody care to tell me where I've gone wrong?
Edit:
To expand on this a bit, the class is not a POD type--it derives from a few abstract base classes and thus has a virtual destructor. However, the array is the only data member, and the usage which broke in the unit test was this:
const int n = 100;
std::vector<UUID> src, dst;
src.reserve(n);
dst.resize(n);
for (int i = 0; i < n; ++i) {
UUID id;
src.push_back(id);
}
for (int i = 0; i < n; ++i) {
dst[i] = src[i];
}
bool good = true;
for (int i = 0; i < n; ++i) {
const bool thisGood = (dst[i] == src[i]);
std::cout << "i = " << i << " -> src = '" << src[i]
<< "', dst = '" << dst[i] << "', src == dst ? "
<< thisGood << '\n';
good = (good && thisGood);
}
