[Bug tree-optimization/105237] New: Missing uninitialized warning in self-initialization case

[nojus.gudinavicius at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105237

            Bug ID: 105237
           Summary: Missing uninitialized warning in self-initialization
                    case
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nojus.gudinavicius at gmail dot com
  Target Milestone: ---

Created attachment 52789
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52789&action=edit
Reproducer source code

Sorry if this is a dup of bug 18501. The other samples seemed to follow
different pattern than mine so I decided to post separately. Anyway:

$ cat t.c
#include <stdio.h>
#include <stdlib.h>

int negate(int n) { return -n; }
void doexit() { exit(0); }

void test() {
    int n;
    while ((n=1) > 0) {
        int n = negate(n); // n used before initialization
        printf("%d\n", n);
        doexit();
    }
}

int main() {
    test();
}
$ gcc -Wall t.c # no warning. replacing doexit call with break shows the
warning

Without the function call the reproducer is smaller, although maybe less likely
to be run into:

int n;
{
    int n = n;
    printf("%d\n", n);
}