* Use lifetimes to check for returning reference to temporaries
* Check for dangling temporaries
* Check for unknown types for returining by reference
* Remove old returnTemporary check
* Format
* Check for deref op
* Ternary operator return an lvalue reference
* Warn when returning temporaries from member functions
* Improve handling of pointer to function
* Extend lifetimes of const references
This will now warn when doing something like this:
```cpp
template <class T, class K, class V>
const V& get_default(const T& t, const K& k, const V& v) {
auto it = t.find(k);
if (it == t.end()) return v;
return it->second;
}
const int& bar(const std::unordered_map<int, int>& m, int k) {
auto x = 0;
return get_default(m, k, x);
}
```
The lifetime warning is considered inconclusive in this case.
I also updated valueflow to no tinject inconclusive values unless `--inconclusive` flag is passed. This creates some false negatives because library functions are not configured to not modify their input parameters, and there are some checks that do not check if the value is inconclusive or not.
This fixes the issue by making `ProgramMemory` keep track of values based on the conditions.
It also removes the `deadpointer` check since it duplicates the `invalidLifetime` check.
This switches to use lifetime analysis to check for assigning to non-local variables:
```cpp
class test
{
public:
void f()
{
int x;
this->ptr = &x;
}
protected:
int *ptr;
};
```
This fixes issue 8996 by improving the alias checking by using lifetime analysis. It also extends the lifetime checker to handle constructors and initializer lists for containers and arrays.
This will now warn for cases like this:
```cpp
auto& f() {
std::vector<int> x;
return x[0];
}
```
It also improves the handling of address of operator, so it can now warn across some function calls, like this:
```cpp
int& f(int& a) {
return a;
}
int* hello() {
int x = 0;
return &f(x);
}
```
Even if `ptr` is a local variable, the object `ptr->item` might be not.
So taking address of `ptr->item` is definitely not unsafe in general.
This commit fixes false positives triggered by commit
1.85-249-gf42648fe2 on the following code of sssd:
https://github.com/SSSD/sssd/blob/d409df33/src/sbus/request/sbus_request.c#L359
This will use the lifetime checker for dangling references. It will find these cases for indirectly assigned reference:
```cpp
int &foo()
{
int s = 0;
int& x = s;
return x;
}
```
This will also fix issue 510 as well:
```cpp
int &f( int k )
{
static int &r = k;
return r;
}
```
This fixes issue in:
```cpp
void f()
{
char stack[512];
RGNDATA *data;
if (data_size > sizeof (stack))
data = malloc (data_size);
else
data = (RGNDATA *)stack;
if ((char *)data != stack)
free (data); // <- data is not stack
}
```
It seems the `ProgramMemory` can't handle two known values(such as int and tok) together. So instead `ValueFlowAfterAssign` runs `ValueFlowForward` with tok values and then runs it with the other values.
Paul Fultz II
Rikard Falkeborn
Daniel Marjamäki
Frank Zingsheim
amai2012
Kamil Dudka
practicalswift