* c-decl.c (named_labels, shadowed_labels, label_level_chain)

	(push_label_level, pop_label_level): Kill.
	(struct binding_level): Rename level_chain to outer.
	Add outer_function field.  Change parm_flag, function_body,
	keep, keep_if_subblocks to 1-bit bitfields of type bool.
	(current_function_level): New variable.
	(keep_next_level_flag, keep_next_if_subblocks): Change type to bool.
	(keep_next_level, declare_parm_level, warn_if_shadowing):
	Update to match.
	(struct language_function): Kill named_labels, shadowed_labels fields.
	(c_init_decl_processing, start_function, c_push__function_context)
	(c_pop_function_context): No need to muck with named_labels nor
	shadowed_labels.

	(make_binding_level): No need to clear the structure here.
	(pop_binding_level): Always operate on current_binding_level.
	Update current_function_level if necessary.
	(pushlevel): Don't clear named_labels.  Update current_function_level
	if necessary.  Use "true" and "false" where appropriate.
	(poplevel): Diagnose labels defined but not used, or vice
	versa, and clear out label-meanings leaving scope, while
	walking down the decls list, for all binding levels.
	Handle LABEL_DECLs appearing in the shadowed list.
	pop_binding_level takes no arguments.
	(pushdecl_function_level): Use current_function_level.

	(make_label, bind_label): New static functions.
	(declare_label): New exported function.
	(lookup_label, define_label): Rewritten for new data structure.
	(shadow_label): Kill.

	* c-tree.h: Prototype declare_label; don't prototype
	push_label_level, pop_label_level, nor shadow_label.
	* c-parse.in: Remove all calls to push_label_level and
	pop_label_level.  Use declare_label for __label__ decls.

	* doc/extend.texi: Clarify that __label__ can be used to
	declare labels with local scope in any nested block, not
	just statement expressions.  Cross-reference nested functions
	section from local labels section.

testsuite:
	* gcc.dg/noncompile/label-1.c: New comprehensive test case for
	diagnostics of ill-formed constructs involving labels.
	* gcc.dg/noncompile/label-lineno-1.c: Add error regexp for
	the new 'previously defined here' message.

From-SVN: r69597

gcc/ChangeLog

+2003-07-19  Zack Weinberg  <zack@codesourcery.com>
+
+	* c-decl.c (named_labels, shadowed_labels, label_level_chain)
+	(push_label_level, pop_label_level): Kill.
+	(struct binding_level): Rename level_chain to outer.
+	Add outer_function field.  Change parm_flag, function_body,
+	keep, keep_if_subblocks to 1-bit bitfields of type bool.
+	(current_function_level): New variable.
+	(keep_next_level_flag, keep_next_if_subblocks): Change type to bool.
+	(keep_next_level, declare_parm_level, warn_if_shadowing):
+	Update to match.
+	(struct language_function): Kill named_labels, shadowed_labels fields.
+	(c_init_decl_processing, start_function, c_push__function_context)
+	(c_pop_function_context): No need to muck with named_labels nor
+	shadowed_labels.
+
+	(make_binding_level): No need to clear the structure here.
+	(pop_binding_level): Always operate on current_binding_level.
+	Update current_function_level if necessary.
+	(pushlevel): Don't clear named_labels.  Update current_function_level
+	if necessary.  Use "true" and "false" where appropriate.
+	(poplevel): Diagnose labels defined but not used, or vice
+	versa, and clear out label-meanings leaving scope, while
+	walking down the decls list, for all binding levels.
+	Handle LABEL_DECLs appearing in the shadowed list.
+	pop_binding_level takes no arguments.
+	(pushdecl_function_level): Use current_function_level.
+
+	(make_label, bind_label): New static functions.
+	(declare_label): New exported function.
+	(lookup_label, define_label): Rewritten for new data structure.
+	(shadow_label): Kill.
+
+	* c-tree.h: Prototype declare_label; don't prototype
+	push_label_level, pop_label_level, nor shadow_label.
+	* c-parse.in: Remove all calls to push_label_level and
+	pop_label_level.  Use declare_label for __label__ decls.
+
+	* doc/extend.texi: Clarify that __label__ can be used to
+	declare labels with local scope in any nested block, not
+	just statement expressions.  Cross-reference nested functions
+	section from local labels section.
+
 2003-07-19  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
 
 	* sched-rgn.c (find_rgns): Initialize current_edge correctly.
@@ -13,7 +56,7 @@
 
 2003-07-19  Ulrich Weigand  <uweigand@de.ibm.com>
 
-	* config/s390/s390.c (legitimize_pic_address): Access local symbols 
+	* config/s390/s390.c (legitimize_pic_address): Access local symbols
 	relative to the GOT instead of relative to the literal pool base.
 	(s390_output_symbolic_const): Handle new GOT-relative accesses.
 	* config/s390/s390.md ("call"): Access local functions and PLT stubs
@@ -21,7 +64,7 @@
 	("call_value"): Likewise.
 	("call_value_tls"): Likewise.
 
-	* config/s390/s390.c (s390_chunkify_start): Remove pool anchor 
+	* config/s390/s390.c (s390_chunkify_start): Remove pool anchor
 	reloading.  Support LTREL_BASE / LTREL_OFFSET construct.
 	(s390_chunkify_finish): Likewise.
 	(s390_chunkify_cancel): Likewise.
@@ -40,12 +83,12 @@
 	* config/s390/s390.c (s390_split_branches): Use LTREL_BASE/OFFSET.
 	(s390_load_got): New function.  Use LTREL_BASE/OFFSET.
 	(s390_emit_prologue): Use it.
-	* config/s390/s390.md ("builtin_longjmp", "builtin_setjmp_setup", 
-	"builtin_setjmp_receiver"): Cleanup.  Use s390_load_got.  Do not 
+	* config/s390/s390.md ("builtin_longjmp", "builtin_setjmp_setup",
+	"builtin_setjmp_receiver"): Cleanup.  Use s390_load_got.  Do not
 	hard-code register 14.
 	* config/s390/s390-protos.h (s390_load_got): Declare.
 
-	* config/s390/s390.c (NR_C_MODES, constant_modes, gen_consttable): 
+	* config/s390/s390.c (NR_C_MODES, constant_modes, gen_consttable):
 	Support TImode constants.
 	* config/s390/s390.md ("consttable_ti"): New.
 	("consttable_si", "consttable_di"): Handle TLS symbols correctly.
@@ -61,7 +104,7 @@
 	"pool_start_64", "pool_end_64", "reload_base_31", "reload_base_64",
 	"pool", "literal_pool_31", "literal_pool_64"): Cleanup.  Use
 	symbolic UNSPEC values.
-	* config/s390/s390.c (larl_operand, s390_short_displacement, 
+	* config/s390/s390.c (larl_operand, s390_short_displacement,
 	bras_sym_operand, s390_cannot_force_const_mem,
 	s390_delegitimize_address, s390_decompose_address,
 	legitimize_pic_address, s390_output_symbolic_const,
@@ -163,7 +206,7 @@
 
 2003-07-18  Kazu Hirata  <kazu@cs.umass.edu>
 
-	* combine.c (simplify_comparison): Don't share rtx when converting 
+	* combine.c (simplify_comparison): Don't share rtx when converting
 	(ne (and (not X) 1) 0) to (eq (and X 1) 0).
 
 2003-07-18  David Edelsohn  <edelsohn@gnu.org>

gcc/c-parse.in

@@ -664,8 +664,6 @@ primary:
 
 		   if (pedantic)
 		     pedwarn ("ISO C forbids braced-groups within expressions");
-		  pop_label_level ();
-
 		  saved_last_tree = COMPOUND_BODY ($1);
 		  RECHAIN_STMTS ($1, COMPOUND_BODY ($1));
 		  last_tree = saved_last_tree;
@@ -677,7 +675,6 @@ primary:
 		}
 	| compstmt_primary_start error ')'
 		{
-		  pop_label_level ();
 		  last_tree = COMPOUND_BODY ($1);
 		  TREE_CHAIN (last_tree) = NULL_TREE;
 		  $$ = error_mark_node;
@@ -2113,7 +2110,7 @@ label_decl:
 		{ tree link;
 		  for (link = $2; link; link = TREE_CHAIN (link))
 		    {
-		      tree label = shadow_label (TREE_VALUE (link));
+		      tree label = declare_label (TREE_VALUE (link));
 		      C_DECLARED_LABEL_FLAG (label) = 1;
 		      add_decl_stmt (label);
 		    }
@@ -2158,7 +2155,6 @@ compstmt_primary_start:
 		     there is a way to turn off the entire subtree of blocks
 		     that are contained in it.  */
 		  keep_next_level ();
-		  push_label_level ();
 		  compstmt_count++;
 		  $$ = add_stmt (build_stmt (COMPOUND_STMT, last_tree));
 		}

gcc/c-tree.h

@@ -197,6 +197,7 @@ extern void clear_parm_order (void);
 extern int  complete_array_type (tree, tree, int);
 extern void declare_parm_level (void);
 extern void undeclared_variable (tree);
+extern tree declare_label (tree);
 extern tree define_label (location_t, tree);
 extern void finish_decl (tree, tree, tree);
 extern tree finish_enum (tree, tree, tree);
@@ -214,13 +215,10 @@ extern void parmlist_tags_warning (void);
 extern void pending_xref_error (void);
 extern void c_push_function_context (struct function *);
 extern void c_pop_function_context (struct function *);
-extern void pop_label_level (void);
-extern void push_label_level (void);
 extern void push_parm_decl (tree);
 extern tree pushdecl_top_level (tree);
 extern void pushtag (tree, tree);
 extern tree set_array_declarator_type (tree, tree, int);
-extern tree shadow_label (tree);
 extern void shadow_tag (tree);
 extern void shadow_tag_warned (tree, int);
 extern tree start_enum (tree);

gcc/doc/extend.texi

@@ -424,7 +424,7 @@ extensions, accepted by GCC in C89 mode and in C++.
 
 @menu
 * Statement Exprs::     Putting statements and declarations inside expressions.
-* Local Labels::        Labels local to a statement-expression.
+* Local Labels::        Labels local to a block.
 * Labels as Values::    Getting pointers to labels, and computed gotos.
 * Nested Functions::    As in Algol and Pascal, lexical scoping of functions.
 * Constructing Calls::	Dispatching a call to another function.
@@ -577,10 +577,10 @@ bug.)
 @cindex local labels
 @cindex macros, local labels
 
-Each statement expression is a scope in which @dfn{local labels} can be
-declared.  A local label is simply an identifier; you can jump to it
-with an ordinary @code{goto} statement, but only from within the
-statement expression it belongs to.
+GCC allows you to declare @dfn{local labels} in any nested block
+scope. A local label is just like an ordinary label, but you can
+only reference it (with a @code{goto} statement, or by taking its
+address) within the block in which it was declared.  
 
 A local label declaration looks like this:
 
@@ -595,21 +595,38 @@ or
 __label__ @var{label1}, @var{label2}, /* @r{@dots{}} */;
 @end example
 
-Local label declarations must come at the beginning of the statement
-expression, right after the @samp{(@{}, before any ordinary
-declarations.
+Local label declarations must come at the beginning of the block,
+before any ordinary declarations or statements.
 
 The label declaration defines the label @emph{name}, but does not define
 the label itself.  You must do this in the usual way, with
 @code{@var{label}:}, within the statements of the statement expression.
 
-The local label feature is useful because statement expressions are
-often used in macros.  If the macro contains nested loops, a @code{goto}
-can be useful for breaking out of them.  However, an ordinary label
-whose scope is the whole function cannot be used: if the macro can be
-expanded several times in one function, the label will be multiply
-defined in that function.  A local label avoids this problem.  For
-example:
+The local label feature is useful for complex macros.  If a macro
+contains nested loops, a @code{goto} can be useful for breaking out of
+them.  However, an ordinary label whose scope is the whole function
+cannot be used: if the macro can be expanded several times in one
+function, the label will be multiply defined in that function.  A
+local label avoids this problem.  For example:
+
+@example
+#define SEARCH(value, array, target)              \
+do @{                                              \
+  __label__ found;                                \
+  typeof (target) _SEARCH_target = (target);      \
+  typeof (*(array)) *_SEARCH_array = (array);     \
+  int i, j;                                       \
+  int value;                                      \
+  for (i = 0; i < max; i++)                       \
+    for (j = 0; j < max; j++)                     \
+      if (_SEARCH_array[i][j] == _SEARCH_target)  \
+        @{ (value) = i; goto found; @}              \
+  (value) = -1;                                   \
+ found:;                                          \
+@} while (0)
+@end example
+
+This could also be written using a statement-expression:
 
 @example
 #define SEARCH(array, target)                     \
@@ -629,6 +646,9 @@ example:
 @})
 @end example
 
+Local label declarations also make the labels they declare visible to
+nested functions, if there are any.  @xref{Nested Functions}, for details.
+
 @node Labels as Values
 @section Labels as Values
 @cindex labels as values

gcc/testsuite/ChangeLog

+2003-07-19  Zack Weinberg  <zack@codesourcery.com>
+
+	* gcc.dg/noncompile/label-1.c: New comprehensive test case for
+	diagnostics of ill-formed constructs involving labels.
+	* gcc.dg/noncompile/label-lineno-1.c: Add error regexp for
+	the new 'previously defined here' message.
+
 2003-07-18  Nathan Sidwell  <nathan@codesourcery.com>
 
 	* g++.dg/parse/non-dependent2.C: New test.
 
 2003-07-18  Andrew Pinski  <pinskia@physics.uc.edu>
 
-	* g++.dg/init/init-ref4.C: xfail on targets without 
+	* g++.dg/init/init-ref4.C: xfail on targets without
 	weak symbols.
 
 2003-07-17  Jakub Jelinek  <jakub@redhat.com>
@@ -278,7 +285,7 @@
 	* g++.dg/opt/emptyunion.C: New testcase.
 
 2003-07-07  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
-            Eric Botcazou  <ebotcazou@libertysurf.fr>
+	    Eric Botcazou  <ebotcazou@libertysurf.fr>
 
 	* g++.dg/opt/stack1.C: New test.
 
@@ -286,7 +293,7 @@
 
 	* g++.old-deja/g++.jason/typeid1.C: Make it a compile test, not a
 	run test.
-	
+
 	PR c++/11431
 	* g++.dg/expr/static_cast3.C: New test.
 

gcc/testsuite/gcc.dg/noncompile/label-1.c

+/* Test various diagnostics of ill-formed constructs involving labels.  */
+/* { dg-do compile } */
+/* { dg-options "-Wunused" } */
+
+extern void dummy(void);
+
+/* labels must be defined */
+void a(void)
+{
+  goto l;   /* { dg-error "used but not defined" "no label" } */
+}
+
+/* warnings for labels defined but not used, or declared but not defined */
+void b(void)
+{
+  __label__ l;
+ l:  /* { dg-warning "defined but not used"  "no goto 1" } */
+ m:  /* { dg-warning "defined but not used"  "no goto 2" } */
+  dummy();
+}
+
+void c(void)
+{
+  __label__ l;  /* { dg-warning "declared but not defined" "only __label__" } */
+  dummy();
+}
+
+/* can't have two labels with the same name in the same function */
+void d(void)
+{
+ l: dummy();  /* { dg-error "previously defined" "prev def same scope" } */
+ l: dummy();  /* { dg-error "duplicate label" "dup label same scope" } */
+ goto l;
+}
+
+/* even at different scopes */
+void e(void)
+{
+ l: dummy();	/* { dg-error "previously defined"  "prev def diff scope" } */
+  {
+  l: dummy();	/* { dg-error "duplicate label" "dup label diff scope" } */
+  }
+  goto l;
+}
+
+/* but, with __label__, you can */
+void f(void)
+{
+ l: dummy();
+  {
+    __label__ l;
+    l: dummy();	  /* { dg-warning "defined but not used" "unused shadow 1" } */
+  };
+  goto l;  /* this reaches the outer l */
+}
+
+/* a __label__ is not visible outside its scope */
+void g(void)
+{
+  dummy();
+  {
+    __label__ l;
+    l: dummy();
+    goto l;
+  }
+  goto l;  /* { dg-error "used but not defined" "label ref out of scope" } */
+}
+
+/* __label__ can appear at top level of a function, too...
+   ... but doesn't provide a definition of the label */
+void h(void)
+{
+  __label__ l;
+  dummy ();
+
+  goto l;  /* { dg-error "used but not defined" "used, only __label__" } */
+}
+
+/* A nested function may not goto a label outside itself  */
+void i(void)
+{
+  auto void nest(void);
+
+ l: nest();
+  
+  void nest(void)
+    {
+      goto l;  /* { dg-error "used but not defined" "nest use outer label" } */
+    }
+
+  goto l; /* reaches the outer l */
+}
+
+/* which means that a nested function may have its own label with the
+   same name as the outer function */
+void j(void)
+{
+  auto void nest(void);
+
+ l: nest();
+  
+  void nest(void)
+    {
+    l: dummy(); /* { dg-warning "defined but not used" "nest label same name" } */
+    }
+
+  goto l; /* reaches the outer l */
+}
+
+/* and, turnabout, an outer function may not goto a label in a nested
+   function */
+void k(void)
+{
+  void nest(void)
+  {
+  l: dummy();  /* { dg-warning "defined but not used" "outer use nest label" } */
+  }
+
+  goto l; /* { dg-error "used but not defined" "outer use nest label" } */
+  nest();
+}
+
+/* not even with __label__ */
+void l(void)
+{
+  void nest(void)
+  {
+    __label__ l;
+  l: dummy(); /* { dg-warning "defined but not used" "outer use nest __label__" } */
+  }
+
+  goto l; /* { dg-error "used but not defined" "outer use nest __label__" } */
+  nest();
+}
+
+
+/* but if the outer label is declared with __label__, then a nested
+   function can goto that label (accomplishing a longjmp) */
+void m(void)
+{
+  __label__ l;
+  void nest(void) { goto l; }
+  nest();
+  dummy();
+ l:;
+}
+
+/* and that means the nested function cannot have its own label with
+   the same name as an outer label declared with __label__ */
+
+void n(void)
+{
+  __label__ l; /* { dg-error "previously declared" "outer label decl" } */
+  void nest(void)
+    {
+    l: goto l;  /* { dg-error "duplicate label" "inner label defn" } */
+    }
+
+ l:
+  nest();
+}
+
+/* unless the nested function uses __label__ too!  */
+void o(void)
+{
+  __label__ l;
+  void nest(void)
+    {
+      __label__ l;
+    l: goto l;
+    }
+
+ l: goto l;
+ nest();
+}

gcc/testsuite/gcc.dg/noncompile/label-lineno-1.c

@@ -4,7 +4,7 @@
 void
 foo(int i)
 {
- my_label:
+ my_label: /* { dg-error "previously defined" "prev label" } */
 
   i++;