re PR c++/772 (Statement expressions issues)

	PR c/772
	PR c/17913
	* c-tree.h (C_DECL_UNJUMPABLE_STMT_EXPR,
	C_DECL_UNDEFINABLE_STMT_EXPR, struct c_label_list, struct
	c_label_context, label_context_stack): New.
	* c-decl.c (define_label): Check for jumps into statement
	expressions.  Add label to list of defined labels.
	(start_function): Push context on label_context_stack.
	(finish_function): Pop context from label_context_stack.
	* c-typeck.c (label_context_stack): New.
	(c_finish_goto_label): Check for jumps into statement
	expressions.  Add label to list of jumped to labels.
	(struct c_switch): Add blocked_stmt_expr.
	(c_start_case): Initialize it.
	(do_case): Check it.
	(c_finish_case): Verify !blocked_stmt_expr.
	(c_begin_stmt_expr):  Push context on label_context_stack.
	Increment blocked_stmt_expr.  Mark labels jumped to from outside
	as undefinable.
	(c_finish_stmt_expr): December blocked_stmt_expr.  Mark labels
	defined in the statement expression and no longer jumpable to.
	Mark labels jumped to from just outside the statement expression
	as again definable.  Pop context from label_context_stack.
	* doc/extend.texi (Statement Exprs): Update.

objc:
	* objc-act.c (objc_start_function): Push context on
	label_context_stack.

testsuite:
	* gcc.dg/stmt-expr-label-1.c, gcc.dg/stmt-expr-label-2.c,
	gcc.dg/stmt-expr-label-3.c : New tests.
	* gcc.c-torture/execute/medce-2.c: Remove.

From-SVN: r97273

gcc/ChangeLog

 2005-03-30  Joseph S. Myers  <joseph@codesourcery.com>
 
+	PR c/772
+	PR c/17913
+	* c-tree.h (C_DECL_UNJUMPABLE_STMT_EXPR,
+	C_DECL_UNDEFINABLE_STMT_EXPR, struct c_label_list, struct
+	c_label_context, label_context_stack): New.
+	* c-decl.c (define_label): Check for jumps into statement
+	expressions.  Add label to list of defined labels.
+	(start_function): Push context on label_context_stack.
+	(finish_function): Pop context from label_context_stack.
+	* c-typeck.c (label_context_stack): New.
+	(c_finish_goto_label): Check for jumps into statement
+	expressions.  Add label to list of jumped to labels.
+	(struct c_switch): Add blocked_stmt_expr.
+	(c_start_case): Initialize it.
+	(do_case): Check it.
+	(c_finish_case): Verify !blocked_stmt_expr.
+	(c_begin_stmt_expr):  Push context on label_context_stack.
+	Increment blocked_stmt_expr.  Mark labels jumped to from outside
+	as undefinable.
+	(c_finish_stmt_expr): December blocked_stmt_expr.  Mark labels
+	defined in the statement expression and no longer jumpable to.
+	Mark labels jumped to from just outside the statement expression
+	as again definable.  Pop context from label_context_stack.
+	* doc/extend.texi (Statement Exprs): Update.
+
+2005-03-30  Joseph S. Myers  <joseph@codesourcery.com>
+
 	PR c/20368
 	* c-decl.c (start_function): Check for old_decl being
 	error_mark_node.

gcc/c-decl.c

@@ -2440,6 +2440,7 @@ define_label (location_t location, tree name)
      if there is a containing function with a declared label with
      the same name.  */
   tree label = I_LABEL_DECL (name);
+  struct c_label_list *nlist;
 
   if (label
       && ((DECL_CONTEXT (label) == current_function_decl
@@ -2456,6 +2457,8 @@ define_label (location_t location, tree name)
       /* The label has been used or declared already in this function,
 	 but not defined.  Update its location to point to this
 	 definition.  */
+      if (C_DECL_UNDEFINABLE_STMT_EXPR (label))
+	error ("%Jjump into statement expression", label);
       DECL_SOURCE_LOCATION (label) = location;
     }
   else
@@ -2472,6 +2475,11 @@ define_label (location_t location, tree name)
     warning ("%Htraditional C lacks a separate namespace for labels, "
              "identifier %qE conflicts", &location, name);
 
+  nlist = XOBNEW (&parser_obstack, struct c_label_list);
+  nlist->next = label_context_stack->labels_def;
+  nlist->label = label;
+  label_context_stack->labels_def = nlist;
+
   /* Mark label as having been defined.  */
   DECL_INITIAL (label) = error_mark_node;
   return label;
@@ -5631,6 +5639,7 @@ start_function (struct c_declspecs *declspecs, struct c_declarator *declarator,
 {
   tree decl1, old_decl;
   tree restype, resdecl;
+  struct c_label_context *nstack;
 
   current_function_returns_value = 0;  /* Assume, until we see it does.  */
   current_function_returns_null = 0;
@@ -5639,6 +5648,12 @@ start_function (struct c_declspecs *declspecs, struct c_declarator *declarator,
   current_extern_inline = 0;
   c_switch_stack = NULL;
 
+  nstack = XOBNEW (&parser_obstack, struct c_label_context);
+  nstack->labels_def = NULL;
+  nstack->labels_used = NULL;
+  nstack->next = label_context_stack;
+  label_context_stack = nstack;
+
   /* Indicate no valid break/continue context by setting these variables
      to some non-null, non-label value.  We'll notice and emit the proper
      error message in c_finish_bc_stmt.  */
@@ -6220,6 +6235,8 @@ finish_function (void)
 {
   tree fndecl = current_function_decl;
 
+  label_context_stack = label_context_stack->next;
+
   if (TREE_CODE (fndecl) == FUNCTION_DECL
       && targetm.calls.promote_prototypes (TREE_TYPE (fndecl)))
     {

gcc/c-tree.h

@@ -106,6 +106,17 @@ struct lang_type GTY(())
    sizeof and typeof it is set for other function decls as well.  */
 #define C_DECL_USED(EXP) DECL_LANG_FLAG_5 (EXP)
 
+/* Record whether a label was defined in a statement expression which
+   has finished and so can no longer be jumped to.  */
+#define C_DECL_UNJUMPABLE_STMT_EXPR(EXP)	\
+  DECL_LANG_FLAG_6 (LABEL_DECL_CHECK (EXP))
+
+/* Record whether a label was the subject of a goto from outside the
+   current level of statement expression nesting and so cannot be
+   defined right now.  */
+#define C_DECL_UNDEFINABLE_STMT_EXPR(EXP)	\
+  DECL_LANG_FLAG_7 (LABEL_DECL_CHECK (EXP))
+
 /* Nonzero for a decl which either doesn't exist or isn't a prototype.
    N.B. Could be simplified if all built-in decls had complete prototypes
    (but this is presently difficult because some of them need FILE*).  */
@@ -350,6 +361,27 @@ struct language_function GTY(())
   int extern_inline;
 };
 
+/* Save lists of labels used or defined in particular statement
+   expression contexts.  Allocated on the parser obstack.  */
+
+struct c_label_list
+{
+  /* The label at the head of the list.  */
+  tree label;
+  /* The rest of the list.  */
+  struct c_label_list *next;
+};
+
+struct c_label_context
+{
+  /* The labels defined at this level of nesting.  */
+  struct c_label_list *labels_def;
+  /* The labels used at this level of nesting.  */
+  struct c_label_list *labels_used;
+  /* The next outermost context.  */
+  struct c_label_context *next;
+};
+
 
 /* in c-parser.c */
 extern void c_parse_init (void);
@@ -452,6 +484,7 @@ extern int in_sizeof;
 extern int in_typeof;
 
 extern struct c_switch *c_switch_stack;
+extern struct c_label_context *label_context_stack;
 
 extern tree require_complete_type (tree);
 extern int same_translation_unit_p (tree, tree);

gcc/c-typeck.c

@@ -64,6 +64,8 @@ int in_sizeof;
 /* The level of nesting inside "typeof".  */
 int in_typeof;
 
+struct c_label_context *label_context_stack;
+
 /* Nonzero if we've already printed a "missing braces around initializer"
    message within this initializer.  */
 static int missing_braces_mentioned;
@@ -6478,6 +6480,23 @@ c_finish_goto_label (tree label)
   if (!decl)
     return NULL_TREE;
 
+  if (C_DECL_UNJUMPABLE_STMT_EXPR (decl))
+    {
+      error ("jump into statement expression");
+      return NULL_TREE;
+    }
+
+  if (!C_DECL_UNDEFINABLE_STMT_EXPR (decl))
+    {
+      /* No jump from outside this statement expression context, so
+	 record that there is a jump from within this context.  */
+      struct c_label_list *nlist;
+      nlist = XOBNEW (&parser_obstack, struct c_label_list);
+      nlist->next = label_context_stack->labels_used;
+      nlist->label = decl;
+      label_context_stack->labels_used = nlist;
+    }
+
   TREE_USED (decl) = 1;
   return add_stmt (build1 (GOTO_EXPR, void_type_node, decl));
 }
@@ -6604,6 +6623,11 @@ struct c_switch {
      of the GNU case range extension.  */
   splay_tree cases;
 
+  /* Number of nested statement expressions within this switch
+     statement; if nonzero, case and default labels may not
+     appear.  */
+  unsigned int blocked_stmt_expr;
+
   /* The next node on the stack.  */
   struct c_switch *next;
 };
@@ -6658,6 +6682,7 @@ c_start_case (tree exp)
   cs->switch_stmt = build_stmt (SWITCH_STMT, exp, NULL_TREE, orig_type);
   cs->orig_type = orig_type;
   cs->cases = splay_tree_new (case_compare, NULL, NULL);
+  cs->blocked_stmt_expr = 0;
   cs->next = c_switch_stack;
   c_switch_stack = cs;
 
@@ -6671,7 +6696,7 @@ do_case (tree low_value, tree high_value)
 {
   tree label = NULL_TREE;
 
-  if (c_switch_stack)
+  if (c_switch_stack && !c_switch_stack->blocked_stmt_expr)
     {
       label = c_add_case_label (c_switch_stack->cases,
 				SWITCH_STMT_COND (c_switch_stack->switch_stmt),
@@ -6680,6 +6705,15 @@ do_case (tree low_value, tree high_value)
       if (label == error_mark_node)
 	label = NULL_TREE;
     }
+  else if (c_switch_stack && c_switch_stack->blocked_stmt_expr)
+    {
+      if (low_value)
+	error ("case label in statement expression not containing "
+	       "enclosing switch statement");
+      else
+	error ("%<default%> label in statement expression not containing "
+	       "enclosing switch statement");
+    }
   else if (low_value)
     error ("case label not within a switch statement");
   else
@@ -6697,6 +6731,8 @@ c_finish_case (tree body)
 
   SWITCH_STMT_BODY (cs->switch_stmt) = body;
 
+  gcc_assert (!cs->blocked_stmt_expr);
+
   /* Emit warnings as needed.  */
   c_do_switch_warnings (cs->cases, cs->switch_stmt);
 
@@ -6963,12 +6999,30 @@ tree
 c_begin_stmt_expr (void)
 {
   tree ret;
+  struct c_label_context *nstack;
+  struct c_label_list *glist;
 
   /* We must force a BLOCK for this level so that, if it is not expanded
      later, there is a way to turn off the entire subtree of blocks that
      are contained in it.  */
   keep_next_level ();
   ret = c_begin_compound_stmt (true);
+  if (c_switch_stack)
+    {
+      c_switch_stack->blocked_stmt_expr++;
+      gcc_assert (c_switch_stack->blocked_stmt_expr != 0);
+    }
+  for (glist = label_context_stack->labels_used;
+       glist != NULL;
+       glist = glist->next)
+    {
+      C_DECL_UNDEFINABLE_STMT_EXPR (glist->label) = 1;
+    }
+  nstack = XOBNEW (&parser_obstack, struct c_label_context);
+  nstack->labels_def = NULL;
+  nstack->labels_used = NULL;
+  nstack->next = label_context_stack;
+  label_context_stack = nstack;
 
   /* Mark the current statement list as belonging to a statement list.  */
   STATEMENT_LIST_STMT_EXPR (ret) = 1;
@@ -6981,8 +7035,36 @@ c_finish_stmt_expr (tree body)
 {
   tree last, type, tmp, val;
   tree *last_p;
+  struct c_label_list *dlist, *glist, *glist_prev = NULL;
 
   body = c_end_compound_stmt (body, true);
+  if (c_switch_stack)
+    {
+      gcc_assert (c_switch_stack->blocked_stmt_expr != 0);
+      c_switch_stack->blocked_stmt_expr--;
+    }
+  /* It is no longer possible to jump to labels defined within this
+     statement expression.  */
+  for (dlist = label_context_stack->labels_def;
+       dlist != NULL;
+       dlist = dlist->next)
+    {
+      C_DECL_UNJUMPABLE_STMT_EXPR (dlist->label) = 1;
+    }
+  /* It is again possible to define labels with a goto just outside
+     this statement expression.  */
+  for (glist = label_context_stack->next->labels_used;
+       glist != NULL;
+       glist = glist->next)
+    {
+      C_DECL_UNDEFINABLE_STMT_EXPR (glist->label) = 0;
+      glist_prev = glist;
+    }
+  if (glist_prev != NULL)
+    glist_prev->next = label_context_stack->labels_used;
+  else
+    label_context_stack->next->labels_used = label_context_stack->labels_used;
+  label_context_stack = label_context_stack->next;
 
   /* Locate the last statement in BODY.  See c_end_compound_stmt
      about always returning a BIND_EXPR.  */

gcc/doc/extend.texi

@@ -187,6 +187,29 @@ work with C++.  (Note that some versions of the GNU C Library contained
 header files using statement-expression that lead to precisely this
 bug.)
 
+Jumping into a statement expression with @code{goto} or using a
+@code{switch} statement outside the statement expression with a
+@code{case} or @code{default} label inside the statement expression is
+not permitted.  Jumping into a statement expression with a computed
+@code{goto} (@pxref{Labels as Values}) yields undefined behavior.
+Jumping out of a statement expression is permitted, but if the
+statement expression is part of a larger expression then it is
+unspecified which other subexpressions of that expression have been
+evaluated except where the language definition requires certain
+subexpressions to be evaluated before or after the statement
+expression.  In any case, as with a function call the evaluation of a
+statement expression is not interleaved with the evaluation of other
+parts of the containing expression.  For example,
+
+@smallexample
+  foo (), ((@{ bar1 (); goto a; 0; @}) + bar2 ()), baz();
+@end smallexample
+
+@noindent
+will call @code{foo} and @code{bar1} and will not call @code{baz} but
+may or may not call @code{bar2}.  If @code{bar2} is called, it will be
+called after @code{foo} and before @code{bar1}
+
 @node Local Labels
 @section Locally Declared Labels
 @cindex local labels

gcc/objc/ChangeLog

+2005-03-30  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c/772
+	PR c/17913
+	* objc-act.c (objc_start_function): Push context on
+	label_context_stack.
+
 2005-03-23  Joseph S. Myers  <joseph@codesourcery.com>
 
 	* objc-act.c (next_sjlj_build_enter_and_setjmp,

gcc/objc/objc-act.c

@@ -7666,6 +7666,12 @@ objc_start_function (tree name, tree type, tree attrs,
   cplus_decl_attributes (&fndecl, attrs, 0);
   start_preparsed_function (fndecl, attrs, /*flags=*/SF_DEFAULT);
 #else
+  struct c_label_context *nstack;
+  nstack = XOBNEW (&parser_obstack, struct c_label_context);
+  nstack->labels_def = NULL;
+  nstack->labels_used = NULL;
+  nstack->next = label_context_stack;
+  label_context_stack = nstack;
   decl_attributes (&fndecl, attrs, 0);
   announce_function (fndecl);
   DECL_INITIAL (fndecl) = error_mark_node;

gcc/testsuite/ChangeLog

 2005-03-30  Joseph S. Myers  <joseph@codesourcery.com>
 
+	PR c/772
+	PR c/17913
+	* gcc.dg/stmt-expr-label-1.c, gcc.dg/stmt-expr-label-2.c,
+	gcc.dg/stmt-expr-label-3.c : New tests.
+	* gcc.c-torture/execute/medce-2.c: Remove.
+
+2005-03-30  Joseph S. Myers  <joseph@codesourcery.com>
+
 	PR c/20368
 	* gcc.dg/pr20368-1.c, gcc.dg/pr20368-2.c, gcc.dg/pr20368-3.c: New
 	tests.

gcc/testsuite/gcc.c-torture/execute/medce-2.c

-
-extern void abort ();
-
-static int ok = 0;
-
-int bar(void)
-{
-  ok |= 1;
-  return 1;
-}
-
-void bat(void)
-{
-  ok |= 2;
-}
-
-void baz(void)
-{
-  ok |= 4;
-}
-
-void foo()
-{
-  goto lab;
-
-  if (0)
-  {
-    if (({lab: bar();}))
-      bat ();
-    else
-      baz ();
-  }
-}
-
-int main()
-{
-  foo();
-  if (ok != 3)
-    abort ();
-  return 0;
-}
-

gcc/testsuite/gcc.dg/stmt-expr-label-2.c

+/* Test for labels in statement expressions: bugs 772 and 17913.
+   switch statements must not jump into statement expressions.  */
+
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+f (int a)
+{
+  switch (a)
+    {
+    case 0:
+    case 1:
+      ({
+      case 2: /* { dg-error "error: case label in statement expression not containing enclosing switch statement" } */
+      default: /* { dg-error "error: 'default' label in statement expression not containing enclosing switch statement" } */
+	switch (a)
+	  {
+	  case 3:
+	  default:
+	    ;
+	  }
+	0;
+      });
+    }
+}

gcc/testsuite/gcc.dg/stmt-expr-label-3.c

+/* Test for labels in statement expressions: bugs 772 and 17913.
+   Test the particular case of bug 17913.  */
+
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void f(void) { 1 ? 1 : ({ a : 1; 1; }); goto a; } /* { dg-error "error: jump into statement expression" } */