[Bug c/106349] New: strlen reimplementation produces infinite loop with -Os

[vincent.riviere at freesbee dot fr via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106349

            Bug ID: 106349
           Summary: strlen reimplementation produces infinite loop with
                    -Os
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vincent.riviere at freesbee dot fr
  Target Milestone: ---
            Target: m68k-elf

Compiling a function named strlen with strlen-like body generates an infinite
loop.

$ cat bug.c
#include <stddef.h>

size_t strlen(const char *str)
{
    size_t n;

    for (n = 0; *str++; n++);

    return n;
}

$ m68k-elf-gcc -S bug.c -o - -Os
#NO_APP
        .file   "bug.c"
        .text
        .align  2
        .globl  strlen
        .type   strlen, @function
strlen:
        jra strlen
        .size   strlen, .-strlen
        .ident  "GCC: (GNU) 12.1.0"

The only generated code is the infinite loop. That's a nonsense.
This issue doesn't occur with -O2.