invoke.texi: Update documentation of -Wshadow.

       PR/44128
       * gcc/doc/invoke.texi: Update documentation of -Wshadow.
       * gcc/cp/name-lookup.c (pushdecl_maybe_friend): Warn when a local
       decl (variable or type) shadows another type.
       * gcc/testsuite/g++.dg/warn/Wshadow-7.C: New test.

From-SVN: r161765

gcc/ChangeLog

+2010-07-02  Le-Chun Wu  <lcwu@google.com>
+
+	PR/44128
+	* doc/invoke.texi: Update documentation of -Wshadow.
+
 2010-07-02  Daniel Jacobowitz  <dan@codesourcery.com>
 	    Julian Brown  <julian@codesourcery.com>
 	    Sandra Loosemore <sandra@codesourcery.com>

gcc/cp/ChangeLog

+2010-07-02  Le-Chun Wu  <lcwu@google.com>
+
+	PR/44128
+	* name-lookup.c (pushdecl_maybe_friend): Warn when a local decl
+	(variable or type) shadows another type.
+
 2010-07-02  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/44780

gcc/cp/name-lookup.c

@@ -1017,10 +1017,22 @@ pushdecl_maybe_friend (tree x, bool is_friend)
 		   /* Inline decls shadow nothing.  */
 		   && !DECL_FROM_INLINE (x)
 		   && (TREE_CODE (oldlocal) == PARM_DECL
-		       || TREE_CODE (oldlocal) == VAR_DECL)
-		   /* Don't check the `this' parameter.  */
-		   && !DECL_ARTIFICIAL (oldlocal)
-		   && !DECL_ARTIFICIAL (x))
+		       || TREE_CODE (oldlocal) == VAR_DECL
+                       /* If the old decl is a type decl, only warn if the
+                          old decl is an explicit typedef or if both the old
+                          and new decls are type decls.  */
+                       || (TREE_CODE (oldlocal) == TYPE_DECL
+                           && (!DECL_ARTIFICIAL (oldlocal)
+                               || TREE_CODE (x) == TYPE_DECL)))
+		   /* Don't check the `this' parameter or internally generated
+                      vars unless it's an implicit typedef (see
+                      create_implicit_typedef in decl.c).  */
+		   && (!DECL_ARTIFICIAL (oldlocal)
+                       || DECL_IMPLICIT_TYPEDEF_P (oldlocal))
+                   /* Don't check for internally generated vars unless
+                      it's an implicit typedef (see create_implicit_typedef
+                      in decl.c).  */
+		   && (!DECL_ARTIFICIAL (x) || DECL_IMPLICIT_TYPEDEF_P (x)))
 	    {
 	      bool nowarn = false;
 
@@ -1081,10 +1093,12 @@ pushdecl_maybe_friend (tree x, bool is_friend)
 
 	  /* Maybe warn if shadowing something else.  */
 	  else if (warn_shadow && !DECL_EXTERNAL (x)
-	      /* No shadow warnings for internally generated vars.  */
-	      && ! DECL_ARTIFICIAL (x)
-	      /* No shadow warnings for vars made for inlining.  */
-	      && ! DECL_FROM_INLINE (x))
+                   /* No shadow warnings for internally generated vars unless
+                      it's an implicit typedef (see create_implicit_typedef
+                      in decl.c).  */
+                   && (! DECL_ARTIFICIAL (x) || DECL_IMPLICIT_TYPEDEF_P (x))
+                   /* No shadow warnings for vars made for inlining.  */
+                   && ! DECL_FROM_INLINE (x))
 	    {
 	      tree member;
 
@@ -1103,7 +1117,13 @@ pushdecl_maybe_friend (tree x, bool is_friend)
 			   x);
 		}
 	      else if (oldglobal != NULL_TREE
-		       && TREE_CODE (oldglobal) == VAR_DECL)
+		       && (TREE_CODE (oldglobal) == VAR_DECL
+                           /* If the old decl is a type decl, only warn if the
+                              old decl is an explicit typedef or if both the
+                              old and new decls are type decls.  */
+                           || (TREE_CODE (oldglobal) == TYPE_DECL
+                               && (!DECL_ARTIFICIAL (oldglobal)
+                                   || TREE_CODE (x) == TYPE_DECL))))
 		/* XXX shadow warnings in outer-more namespaces */
 		{
 		  warning_at (input_location, OPT_Wshadow,

gcc/doc/invoke.texi

@@ -3859,8 +3859,10 @@ Do not warn whenever an @samp{#else} or an @samp{#endif} are followed by text.
 @item -Wshadow
 @opindex Wshadow
 @opindex Wno-shadow
-Warn whenever a local variable shadows another local variable, parameter or
-global variable or whenever a built-in function is shadowed.
+Warn whenever a local variable or type declaration shadows another variable,
+parameter, type, or class member (in C++), or whenever a built-in function
+is shadowed. Note that in C++, the compiler will not warn if a local variable
+shadows a struct/class/enum, but will warn if it shadows an explicit typedef.
 
 @item -Wlarger-than=@var{len}
 @opindex Wlarger-than=@var{len}

gcc/testsuite/ChangeLog

+2010-07-02  Le-Chun Wu  <lcwu@google.com>
+
+	PR/44128
+	* g++.dg/warn/Wshadow-7.C: New test.
+
 2010-07-02  Daniel Jacobowitz  <dan@codesourcery.com>
 	    Julian Brown  <julian@codesourcery.com>
 	    Sandra Loosemore <sandra@codesourcery.com>

gcc/testsuite/g++.dg/warn/Wshadow-7.C

+// PR c++/44128
+// { dg-options "-Wshadow" }
+
+typedef long My_ssize_t;  // { dg-warning "shadowed declaration" }
+typedef int Foo;          // { dg-warning "shadowed declaration" }
+struct Bar1 {             // { dg-bogus "shadowed declaration" }
+  int a;
+};
+struct Bar2 {             // { dg-warning "shadowed declaration" }
+  int a;
+};
+
+void func() {
+  typedef int My_ssize_t; // { dg-warning "shadows a global" }
+  typedef char My_Num;    // { dg-warning "shadowed declaration" }
+  {
+    typedef short My_Num; // { dg-warning "shadows a previous local" }
+  }
+  int Foo;                // { dg-warning "shadows a global" }
+  float Bar1;             // { dg-bogus "shadows a global" }
+  struct Bar2 {           // { dg-warning "shadows a global" }
+    int a;
+  };
+  struct Bar3 {           // { dg-warning "shadowed declaration" }
+    int a;
+  };
+  struct Bar4 {           // { dg-bogus "shadowed declaration" }
+    int a;
+  };
+  {
+    struct Bar3 {         // { dg-warning "shadows a previous local" }
+      int a;
+    };
+    char Bar4;            // { dg-bogus "shadows a previous local" }
+    int My_Num;           // { dg-warning "shadows a previous local" }
+  }
+}