[Bug lto/116220] New: -Wmaybe-uninitialised in lto_obj_begin_section

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116220

            Bug ID: 116220
           Summary: -Wmaybe-uninitialised in lto_obj_begin_section
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
  Target Milestone: ---

```
/var/tmp/portage/sys-devel/gcc-15.0.9999/work/gcc-15.0.9999/gcc/lto/lto-object.cc:
In function ‘lto_obj_begin_section’:
/var/tmp/portage/sys-devel/gcc-15.0.9999/work/gcc-15.0.9999/gcc/lto/lto-object.cc:333:15:
warning: ‘err’ may be used uninitialized [-Wmaybe-uninitialized]
  333 |       if (err == 0)
      |               ^
/var/tmp/portage/sys-devel/gcc-15.0.9999/work/gcc-15.0.9999/gcc/lto/lto-object.cc:320:7:
note: ‘err’ declared here
  320 |   int err;
      |       ^                                                                
                                                                               
                         
/var/tmp/portage/sys-devel/gcc-15.0.9999/work/gcc-15.0.9999/gcc/lto/lto-object.cc:334:21:
warning: ‘errmsg’ may be used uninitialized [-Wmaybe-uninitialized]
  334 |         fatal_error (input_location, "%s", errmsg);
      |                     ^
/var/tmp/portage/sys-devel/gcc-15.0.9999/work/gcc-15.0.9999/gcc/lto/lto-object.cc:319:15:
note: ‘errmsg’ declared here
  319 |   const char *errmsg;
      |               ^
```

```
void
lto_obj_begin_section (const char *name)
{
  struct lto_simple_object *lo;
  int align;
  const char *errmsg;
  int err;

  lo = (struct lto_simple_object *) current_out_file;
  gcc_assert (lo != NULL
              && lo->sobj_r == NULL
              && lo->sobj_w != NULL
              && lo->section == NULL);

  align = ceil_log2 (POINTER_SIZE_UNITS);
  lo->section = simple_object_write_create_section (lo->sobj_w, name, align,
                                                    &errmsg, &err);
  if (lo->section == NULL)
    {
      if (err == 0)
        fatal_error (input_location, "%s", errmsg);
      else
        fatal_error (input_location, "%s: %s", errmsg, xstrerror (errno));
    }
}
```

so, we use errmsg and assume that simple_object_write_create_section always
initialises it if lo->section == NULL.

But in libiberty...
```

simple_object_write_section *
simple_object_write_create_section (simple_object_write *sobj, const char
*name,
                                    unsigned int align,
                                    const char **errmsg ATTRIBUTE_UNUSED,
                                    int *err ATTRIBUTE_UNUSED)
{
  simple_object_write_section *ret;

  ret = XNEW (simple_object_write_section);
  ret->next = NULL;
  ret->name = xstrdup (name);
  ret->align = align;
  ret->buffers = NULL;
  ret->last_buffer = NULL;

  if (sobj->last_section == NULL)
    {
      sobj->sections = ret;
      sobj->last_section = ret;
    }
  else
    {
      sobj->last_section->next = ret;
      sobj->last_section = ret;
    }

  return ret;
}
```

errmsg is completely untouched and marked as unused, even.