[Bug c++/10416] 'unused variable' warning ignores ctor/dtor side-effects

["pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #10 from pinskia at gcc dot gnu dot org  2006-01-23 22:23 -------
(In reply to comment #9)
> Of course, the compiler (more precisely the middle-end) knows that the
> destructor has a side-effect.  But GCC middle-end tends to have little
> knowledge of language specific idioms.  Notice also that a is "used"
> from a very high level abstraction point of view -- not from byte-fiddling
> point of view.  This is another instance of diagnostic PR better handed off
> to the front-end.

Actually the diagnostic is done in the front-end in cp/decl.c in poplevel.

  /* Before we remove the declarations first check for unused variables.  */
  if (warn_unused_variable
      && !processing_template_decl)
    for (decl = getdecls (); decl; decl = TREE_CHAIN (decl))
      if (TREE_CODE (decl) == VAR_DECL
          && ! TREE_USED (decl)
          && ! DECL_IN_SYSTEM_HEADER (decl)
          && DECL_NAME (decl) && ! DECL_ARTIFICIAL (decl))
        warning (0, "unused variable %q+D", decl);


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10416