[Bug fortran/18540] Jumping into blocks gives error rather than warning

["steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #9 from steven at gcc dot gnu dot org  2006-01-08 21:45 -------
Actually we already know for sure that the label exists and that it is a valid
jump target.  From resolve_branch:

  /* Step one: is this a valid branching target?  */

  if (lp->defined == ST_LABEL_UNKNOWN)
    {
      gfc_error ("Label %d referenced at %L is never defined", lp->value,
                 &lp->where);
      return;
    }

  if (lp->defined != ST_LABEL_TARGET)
    {
      gfc_error ("Statement at %L is not a valid branch target statement "
                 "for the branch statement at %L", &lp->where, &code->loc);
      return;
    }

  /* Step two: make sure this branch is not a branch to itself ;-)  */

  if (code->here == label)
    {
      gfc_warning ("Branch at %L causes an infinite loop", &code->loc);
      return;
    }

  /* Step three: Try to find the label in the parse tree. To do this,
     we traverse the tree block-by-block: first the block that
     contains this GOTO, then the block that it is nested in, etc.  We
     can ignore other blocks because branching into another block is
     not allowed.  */

Step three is what we can skip if we want to allow this kind of invalid jumping
around through a program unit.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540