[PATCH][4.6] detect C++ errors to fix 2288 and 18770

[Janis Johnson <janis187@us.ibm.com>]

The ISO C++ standard says, in Section 3.3.2 sentence 4, that a name
declared in the for-init-statement or in the condition of an if, for
while, or switch statement can't be redeclared in the outermost block
of the controlled statement (this is not an error in C).  This patch
detects those errors that were not already detected elsewhere, adds
a new test, and removes xfails from an existing test.

Tested on powerpc64-linux with bootstrap of all languages but Ada and
regtest for -m32/-m64.  OK for stage 1 of GCC 4.6?

2010-03-18  Janis Johnson  <janis187@us.ibm.com>

gcc/cp
	PR c++/2288
	PR c++/18770
	* name-lookup.h (enum scope_kind): Add sk_cond.
	* name-lookup.c (pushdecl_maybe_friend): Get scope of shadowed local.
	Detect and report error for redeclaration from for-init or if
	or switch condition.
	(begin_scope): Handle sk_cond.
	* semantics.c (begin_if_stmt): Use sk_cond.
	(begin switch_stmt): Ditto.

gcc/testsuite/
	PR c++/2288
	PR c++/18770
	* g++.old-deja/g++.jason/cond.C: Remove xfails.
	* g++.dg/parse/pr18770.C: New test.

Index: gcc/cp/name-lookup.h
===================================================================
--- gcc/cp/name-lookup.h	(revision 157490)
+++ gcc/cp/name-lookup.h	(working copy)
@@ -109,6 +109,8 @@ typedef enum scope_kind {
   sk_catch,	     /* A catch-block.  */
   sk_for,	     /* The scope of the variable declared in a
 			for-init-statement.  */
+  sk_cond,	     /* The scope of the variable declared in the condition
+			of an if or switch statement.  */
   sk_function_parms, /* The scope containing function parameters.  */
   sk_class,	     /* The scope containing the members of a class.  */
   sk_scoped_enum,    /* The scope containing the enumertors of a C++0x
Index: gcc/cp/name-lookup.c
===================================================================
--- gcc/cp/name-lookup.c	(revision 157490)
+++ gcc/cp/name-lookup.c	(working copy)
@@ -946,8 +946,15 @@ pushdecl_maybe_friend (tree x, bool is_f
       else
 	{
 	  /* Here to install a non-global value.  */
-	  tree oldlocal = innermost_non_namespace_value (name);
 	  tree oldglobal = IDENTIFIER_NAMESPACE_VALUE (name);
+	  tree oldlocal = NULL_TREE;
+	  cxx_scope *oldscope = NULL;
+	  cxx_binding *oldbinding = outer_binding (name, NULL, true);
+	  if (oldbinding)
+	    {
+	      oldlocal = oldbinding->value;
+	      oldscope = oldbinding->scope;
+	    }
 
 	  if (need_new_binding)
 	    {
@@ -1051,6 +1058,21 @@ pushdecl_maybe_friend (tree x, bool is_f
 		}
 	    }
 
+	  /* Error if redeclaring a local declared in a for-init-statement
+	     or in the condition of an if or switch statement when the new
+	     declaration is in the outermost block of the controlled
+	     statement.  Redeclaring a variable from a for or while
+	     condition is detected elsewhere.  */
+	  else if (oldlocal != NULL_TREE
+		   && TREE_CODE (oldlocal) == VAR_DECL
+		   && oldscope == current_binding_level->level_chain
+		   && (oldscope->kind == sk_cond
+		       || oldscope->kind == sk_for))
+	    {
+	      error ("redeclaration of %q#D", x);
+	      error ("%q+#D previously declared here", oldlocal);
+	    }
+
 	  /* Maybe warn if shadowing something else.  */
 	  else if (warn_shadow && !DECL_EXTERNAL (x)
 	      /* No shadow warnings for internally generated vars.  */
@@ -1383,6 +1405,7 @@ begin_scope (scope_kind kind, tree entit
     case sk_try:
     case sk_catch:
     case sk_for:
+    case sk_cond:
     case sk_class:
     case sk_scoped_enum:
     case sk_function_parms:
Index: gcc/cp/semantics.c
===================================================================
--- gcc/cp/semantics.c	(revision 157490)
+++ gcc/cp/semantics.c	(working copy)
@@ -644,7 +644,7 @@ tree
 begin_if_stmt (void)
 {
   tree r, scope;
-  scope = do_pushlevel (sk_block);
+  scope = do_pushlevel (sk_cond);
   r = build_stmt (input_location, IF_STMT, NULL_TREE, NULL_TREE, NULL_TREE);
   TREE_CHAIN (r) = scope;
   begin_cond (&IF_COND (r));
@@ -929,7 +929,7 @@ begin_switch_stmt (void)
 
   r = build_stmt (input_location, SWITCH_STMT, NULL_TREE, NULL_TREE, NULL_TREE);
 
-  scope = do_pushlevel (sk_block);
+  scope = do_pushlevel (sk_cond);
   TREE_CHAIN (r) = scope;
   begin_cond (&SWITCH_STMT_COND (r));
 
Index: gcc/testsuite/g++.old-deja/g++.jason/cond.C
===================================================================
--- gcc/testsuite/g++.old-deja/g++.jason/cond.C	(revision 157490)
+++ gcc/testsuite/g++.old-deja/g++.jason/cond.C	(working copy)
@@ -6,14 +6,14 @@ int main()
 {
   float i;
   
-  if (int i = 1)		// { dg-error "" "" { xfail *-*-* } } , 
+  if (int i = 1)		// { dg-error "previously" }
     {
-      char i;			// { dg-error "" "" { xfail *-*-* } } , 
+      char i;			// { dg-error "redeclaration" } 
       char j;
     }
   else
     {
-      short i;			// { dg-error "" "" { xfail *-*-* } } , 
+      short i;			// { dg-error "redeclaration" }
       char j;
     }
 
@@ -27,10 +27,10 @@ int main()
       int i;			// { dg-error "redeclaration" }
     }
 
-  switch (int i = 0)		// { dg-error "" "" { xfail *-*-* } } 
+  switch (int i = 0)		// { dg-error "previously" }
     {
     default:
-      int i;			// { dg-error "" "" { xfail *-*-* } } 
+      int i;			// { dg-error "redeclaration" } 
     }
 
   if (struct A { operator int () { return 1; } } *foo = new A) // { dg-error "defined" } 
Index: gcc/testsuite/g++.dg/parse/pr18770.C
===================================================================
--- gcc/testsuite/g++.dg/parse/pr18770.C	(revision 0)
+++ gcc/testsuite/g++.dg/parse/pr18770.C	(revision 0)
@@ -0,0 +1,175 @@
+/* { dg-do compile } */
+
+/* The ISO C++ standard says, in Section 3.3.2 sentence 4, that a name
+   declared in the for-init-statement or in the condition of an if, for
+   while, or switch statement can't be redeclared in the outermost block
+   of the controlled statement.  (Note, this is not an error in C.)  */
+
+extern void foo (int);
+extern int j;
+
+void
+e0 (void)
+{
+  for (int i = 0;	// { dg-error "previously declared here" "prev" }
+       i < 10; ++i)
+    {
+      int i = 2;	// { dg-error "redeclaration" "redecl" }
+      foo (i);
+    }
+}
+
+void
+e1 (void)
+{
+  int i;
+  for (i = 0;
+       int k = j; i++)	// { dg-error "previously declared here" "prev" }
+    {
+      int k = 2;	// { dg-error "redeclaration" "redecl" }
+      foo (k);
+    }
+}
+
+void
+e2 (void)
+{
+  if (int i = 1)	// { dg-error "previously declared here" "prev" }
+    {
+      int i = 2;	// { dg-error "redeclaration" "redecl" }
+      foo (i);
+    }
+}
+
+void
+e3 (void)
+{
+  if (int i = 1)	// { dg-error "previously declared here" "prev" }
+    {
+      foo (i);
+    }
+  else
+    {
+      int i = 2;	// { dg-error "redeclaration" "redecl" }
+      foo (i);
+    }
+}
+
+void
+e4 (void)
+{
+  while (int i = 1)	// { dg-error "previously declared here" "prev" }
+    {
+      int i = 2;	// { dg-error "redeclaration" "redecl" }
+      foo (i);
+    }
+}
+
+void
+e5 (void)
+{
+  switch (int i = j)	// { dg-error "previously declared here" "prev" }
+    {
+    int i;		// { dg-error "redeclaration" "redecl" }
+    default:
+      {
+        i = 2;
+        foo (i);
+      }
+    }
+}
+
+void
+f0 (void)
+{
+  for (int i = 0; i < 10; ++i)
+    {
+      foo (i);
+      {
+        int i = 2;	// OK, not outermost block.
+        foo (i);
+      }
+    }
+}
+
+void
+f1 (void)
+{
+  int i;
+  for (i = 0; int k = j; i++)
+    {
+      foo (k);
+      {
+	int k = 2;	// OK, not outermost block.
+	foo (k);
+      }
+    }
+}
+
+void
+f2 (void)
+{
+  if (int i = 1)
+    {
+      foo (i);
+      {
+	int i = 2;	// OK, not outermost block.
+	foo (i);
+      }
+    }
+}
+
+void
+f3 (void)
+{
+  if (int i = 1)
+    {
+      foo (i);
+    }
+  else
+    {
+      foo (i+2);
+      {
+	int i = 2;	// OK, not outermost block.
+	foo (i);
+      }
+    }
+}
+
+void
+f4 (void)
+{
+  while (int i = 1)
+    {
+      foo (i);
+      {
+	int i = 2;	// OK, not outermost block.
+	foo (i);
+      }
+    }
+}
+
+void
+f5 (void)
+{
+  switch (int i = j)
+    {
+    default:
+      {
+        int i = 2;	// OK, not outermost block.
+        foo (i);
+      }
+    }
+}
+
+void
+f6 (void)
+{
+  int i = 1;
+
+  for (int j = 0; j < 10; j++)
+    {
+      int i = 2;	// OK, not variable from for-init.
+      foo (i);
+    }
+}