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V794. The assignment operator should be protected from the case of 'this == &src'.
The analyzer has detected a dangerous copy/move assignment operator that lacks a check for object self-assignment and at the same time contains operations that could cause memory leaks, use of deallocated pointers, and other problems, in case it receives a reference to '*this' as an argument.
Consider the following example:
class C {
char *p;
size_t len;
public:
C& operator = (const C& other) {
delete p;
len = other.len;
p = new char[len];
std::copy(other.p, other.p + len, p);
return *this;
}
};The error will show if 'this == &other' and, therefore, 'p == other.p'. In that case, the uninitialized array will be copied into itself when the 'std::copy' call is executed.
Fixed code:
C& operator = (const C& other) {
if (this == std::addressof(other))
return *this;
delete p;
len = other.len;
p = new char[len];
std::copy(other.p, other.p + len, p);
return *this;
}If, however, you know that no such situation can occur, i.e. the operator has an implicit contract, it is recommended that you formalize this contract as an 'assert' construct:
C& operator = (const C& other) {
MyAssert(this != std::addressof(other));
....
}Note: It is better to use the 'std::addressof' function instead of the '&' operator to check a class for equality to itself. Then the check will work even if the class has overloaded '&' operator.
This diagnostic is classified as:
You can look at examples of errors detected by the V794 diagnostic. |
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