[Bug c++/107106] New: Incorrect use of uninitialized value warning

["jlame646 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107106

            Bug ID: 107106
           Summary: Incorrect use of uninitialized value warning
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jlame646 at gmail dot com
  Target Milestone: ---

The following program with `-fanalyzer` flag produces incorrect warning. Demo:
https://godbolt.org/z/YWd4cKbGc


```

#include <string>

std::string square(int num) {
    return std::to_string(num * num);
}

```

The warning says:

```
<source>: In function 'std::string square(int)':
<source>:4:36: warning: use of uninitialized value '<unknown>' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
    4 |     return std::to_string(num * num);
      |                                    ^
  'std::string square(int)': events 1-2
    |
    |    3 | std::string square(int num) {
    |      |                           ^
    |      |                           |
    |      |                           (1) region created on stack here
    |    4 |     return std::to_string(num * num);
    |      |                                    ~
    |      |                                    |
    |      |                                    (2) use of uninitialized value
'<unknown>' here
    |
<source>:4:36: warning: use of uninitialized value '<unknown>' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
    4 |     return std::to_string(num * num);
      |                                    ^
  'std::string square(int)': events 1-2
    |
    |    3 | std::string square(int num) {
    |      |                           ^
    |      |                           |
    |      |                           (1) region created on stack here
    |    4 |     return std::to_string(num * num);
    |      |                                    ~
    |      |                                    |
    |      |                                    (2) use of uninitialized value
'<unknown>' here
    |
```

On searching for possible dupes, i came across this:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=13025 that may be related to this
bug.