[Bug tree-optimization/122183] New: Missing -Wmaybe-uninitialized

[sjames at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122183

            Bug ID: 122183
           Summary: Missing -Wmaybe-uninitialized
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: false-positive
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
            Blocks: 24639
  Target Milestone: ---

There's a maybe missed-optimisation with a bug I hit a while ago that I keep
thinking about occasionally.

Playing around with it to try get a testcase, a variant gives me this:
```
enum
{
  JSON_TYPE_NULL,
  JSON_TYPE_TEXT
} type;
char *data_val;

void
test_json_istream_read_string ()
{
  long size_val;

  type = JSON_TYPE_TEXT;
  switch (type)
    {
    case JSON_TYPE_TEXT:
      break;
    case JSON_TYPE_NULL:
      size_val = 0;
      break;
    }

  if (size_val > 20 || size_val < 0)
    __builtin_abort ();
}

int
main ()
{
  test_json_istream_read_string ();
}
```

We don't seem to ever emit -Wmaybe-uninitialized for this.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639
[Bug 24639] [meta-bug] bug to track all Wuninitialized issues