[Bug middle-end/108042] New: [10/11/12/13 Regression] weakref on an extern decl is incorrectly ignored

[Bug middle-end/108042] New: [10/11/12/13 Regression] weakref on an extern decl is incorrectly ignored

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108042

            Bug ID: 108042
           Summary: [10/11/12/13 Regression] weakref on an extern decl is
                    incorrectly ignored
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

From:
https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Common-Function-Attributes.html#index-weakref-function-attribute

Without a target given as an argument to weakref or to alias, weakref is
equivalent to weak (in that case the declaration may be extern).

Testcase:
```
void KNOWNNOTOBEAFUNCTION(void) __attribute__((weakref));

int main() {
    if (KNOWNNOTOBEAFUNCTION)
        __builtin_abort();
    else
        return 0;
}
```

This should pass.

[Bug middle-end/108042] [10/11/12/13 Regression] weakref on an extern decl is incorrectly ignored

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108042

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.5.3
      Known to fail|                            |4.6.0

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This started to fail with r169288 .

Reported originally at
https://gcc.gnu.org/pipermail/gcc/2022-December/240283.html .

[Bug middle-end/108042] [10/11/12/13 Regression] weakref on an extern decl is incorrectly ignored

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108042

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-12-11
     Ever confirmed|0                           |1
                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org
   Target Milestone|---                         |10.5
             Status|UNCONFIRMED                 |WAITING

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
t2.c:1:6: warning: 'weakref' attribute should be accompanied with an 'alias'
attribute [-Wattributes]
    1 | void KNOWNNOTOBEAFUNCTION(void) __attribute__((weakref));
      |      ^~~~~~~~~~~~~~~~~~~~

did you want to use __attribute__((weak)) here?  I think this works as
designed.

Note handle_weakref_attribute has

  /* The idea here is that `weakref("name")' mutates into `weakref,
     alias("name")', and weakref without arguments, in turn,
     implicitly adds weak.  */

  if (args)
    { 
      attr = tree_cons (get_identifier ("alias"), args, attr); 
      attr = tree_cons (get_identifier ("weakref"), NULL_TREE, attr);

      *no_add_attrs = true;

      decl_attributes (node, attr, flags);
    }
  else
    { 
      if (lookup_attribute ("alias", DECL_ATTRIBUTES (*node)))
        error_at (DECL_SOURCE_LOCATION (*node),
                  "%qE attribute must appear before %qs attribute",
                  name, "alias");

      /* Can't call declare_weak because it wants this to be TREE_PUBLIC,
         and that isn't supported; and because it wants to add it to
         the list of weak decls, which isn't helpful.  */
      DECL_WEAK (*node) = 1;

but then process_common_attributes does

  tree weakref = lookup_attribute ("weakref", DECL_ATTRIBUTES (decl));

  if (weakref && !lookup_attribute ("alias", DECL_ATTRIBUTES (decl)))
    {
      warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wattributes, 
                  "%<weakref%> attribute should be accompanied with"
                  " an %<alias%> attribute");
      DECL_WEAK (decl) = 0;
      DECL_ATTRIBUTES (decl) = remove_attribute ("weakref",
                                                 DECL_ATTRIBUTES (decl));
    }

this diagnostic does not match the documentation which gives the plain
'weakref' semantics of 'weak'.

[Bug middle-end/108042] [10/11/12/13 Regression] weakref on an extern decl is incorrectly ignored

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108042

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
           Assignee|unassigned at gcc dot gnu.org      |hubicka at gcc dot gnu.org

[Bug middle-end/108042] [11/12/13/14 Regression] weakref on an extern decl is incorrectly ignored

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108042

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.