[patch, fortran] PR24784, PR28004 - about unused variables

[Daniel Franke <franke dot daniel at gmail dot com>]

Depending on the command-line arguments -Wall and -Wextra, gfortran gives 
different kinds of warnings for unused dummy arguments. In addition, 
sometimes the middle-end chimes in and emits a default warning as well 
(PR27484). Further, PR28004 requests a warning if dummy arguments of 
INTENT(out) are not set.

This patch addresses all this in a single sweep, the corrected warnings are 
emitted on -Wall regardless of -Wextra (via warn_unused_variable). The 
changes should be self explanatory, those in function.c probably need to be 
approved by a C- or global maintainer?!


Example:

  SUBROUTINE f(i)
    INTEGER, INTENT(out) :: i
  END SUBROUTINE

before (-Wall):
Warning: Unused variable i declared at (1)

before (-Wall -Wextra):
Warning: Unused parameter i declared at (1)
function.f90:3: warning: unused parameter 'i'

after (-Wall, -Wall -Wextra):
Warning: dummy argument 'i' at (1) was declared INTENT(OUT) but was not set


  SUBROUTINE g(i)
    INTEGER :: i
  END SUBROUTINE

before, same as above
after: Warning: unused dummy argument 'i' at (1)


:ADDPATCH fortran:

gcc:
2007-07-04  Daniel Franke  <franke.daniel@gmail.com>

	* function.c (do_warn_unused_parameter): Do not warn if TREE_NO_WARNING is
	set.

gcc/fortran:
2007-07-04  Daniel Franke  <franke.daniel@gmail.com>

	PR fortran/24784
	PR fortran/28004
	* trans-decl.c (generate_local_decl): Adjusted warning on unused 
	dummy arguments, tell middle-end not to emit additional warnings.


Bootstrapped and regtested c and fortran on i686-pc-linux-gnu.
Ok for trunk?

Regards
	Daniel

Index: function.c
===================================================================
--- function.c	(revision 126214)
+++ function.c	(working copy)
@@ -4287,7 +4287,8 @@
   for (decl = DECL_ARGUMENTS (fn);
        decl; decl = TREE_CHAIN (decl))
     if (!TREE_USED (decl) && TREE_CODE (decl) == PARM_DECL
-	&& DECL_NAME (decl) && !DECL_ARTIFICIAL (decl))
+	&& DECL_NAME (decl) && !DECL_ARTIFICIAL (decl)
+	&& !TREE_NO_WARNING (decl))
       warning (OPT_Wunused_parameter, "unused parameter %q+D", decl);
 }
 
Index: fortran/trans-decl.c
===================================================================
--- fortran/trans-decl.c	(revision 126214)
+++ fortran/trans-decl.c	(working copy)
@@ -2999,14 +2999,21 @@
 
       if (sym->attr.referenced)
         gfc_get_symbol_decl (sym);
-      else if (sym->attr.dummy && warn_unused_parameter)
-	gfc_warning ("Unused parameter %s declared at %L", sym->name,
+      /* INTENT(out) dummy arguments are likely meant to be set.  */
+      else if (warn_unused_variable
+	       && sym->attr.dummy
+	       && sym->attr.intent == INTENT_OUT)
+	gfc_warning ("dummy argument '%s' at %L was declared INTENT(OUT) but was not set",
+		     sym->name, &sym->declared_at);
+      /* Specific warning for unused dummy arguments. */
+      else if (warn_unused_variable && sym->attr.dummy)
+	gfc_warning ("unused dummy argument '%s' at %L", sym->name,
 		     &sym->declared_at);
       /* Warn for unused variables, but not if they're inside a common
 	 block or are use-associated.  */
       else if (warn_unused_variable
 	       && !(sym->attr.in_common || sym->attr.use_assoc))
-	gfc_warning ("Unused variable %s declared at %L", sym->name,
+	gfc_warning ("unused variable '%s' declared at %L", sym->name,
 		     &sym->declared_at);
       /* For variable length CHARACTER parameters, the PARM_DECL already
 	 references the length variable, so force gfc_get_symbol_decl
@@ -3021,6 +3028,11 @@
 	  sym->attr.referenced = 1;
 	  gfc_get_symbol_decl (sym);
 	}
+
+      /* We do not want the middle-end to warn about unused parameters
+         as this was already done above.  */
+      if (sym->attr.dummy && sym->backend_decl != NULL_TREE)
+	  TREE_NO_WARNING(sym->backend_decl) = 1;
     }
 
   if (sym->attr.dummy == 1)