From patchwork Wed Jul 21 03:09:15 2010
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Subject: [C] Fix PR40563
Date: Tue, 20 Jul 2010 17:09:15 -0000
From: Shujing Zhao <pearly.zhao@oracle.com>
X-Patchwork-Id: 59400
Message-Id: <4C4664DB.6040902@oracle.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Cc: "Joseph S. Myers" <joseph@codesourcery.com>,
 Paolo Carlini <paolo.carlini@oracle.com>

Hi,

This patch diagnose uninitialized const field in struct or union when 
-Wc++-compat enabled.

Tested on i686-pc-linux-gnu with no regression.
ok for trunk?
/gcc
2010-07-21  Shujing Zhao  <pearly.zhao@oracle.com>

	PR c/40563
	* c-decl.c (diagnose_uninitialized_cst_member): New function.
	(finish_decl): Use it to issue a -Wc++-compat warning about
	uninitialized const field in struct or union.
	
/gcc/testsuite
2010-07-21  Shujing Zhao  <pearly.zhao@oracle.com>
	PR c/40563
	* gcc.dg/Wcxx-compat-20.c: New test


Index: c-decl.c
===================================================================
--- c-decl.c	(revision 162361)
+++ c-decl.c	(working copy)
@@ -4103,6 +4103,35 @@ start_decl (struct c_declarator *declara
   return tem;
 }
 
+/* Subroutine of finish_decl. Diagnose uninitialized const member of type TYPE.
+   DECL is the original declaration. */
+
+static void
+diagnose_uninitialized_cst_member (tree decl, tree type)
+{
+  tree field;
+  for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
+    {
+      tree field_type;
+      if (TREE_CODE (field) != FIELD_DECL)
+	continue;
+      field_type = strip_array_types (TREE_TYPE (field));	
+
+      if (TYPE_QUALS (field_type) & TYPE_QUAL_CONST)
+        {
+	  warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wc___compat,
+	  	      "uninitialized const member in %qT is invalid in C++",
+		      TREE_TYPE (decl));
+	  inform (DECL_SOURCE_LOCATION (field), "%qD should be initialized", field);
+	}
+
+      if (TREE_CODE (field_type) == RECORD_TYPE
+	  || TREE_CODE (field_type) == UNION_TYPE)
+	diagnose_uninitialized_cst_member (decl, field_type);
+    }
+}
+
+
 /* Finish processing of a declaration;
    install its initial value.
    If ORIGTYPE is not NULL_TREE, it is the original type of INIT.
@@ -4420,11 +4449,16 @@ finish_decl (tree decl, location_t init_
 
   if (warn_cxx_compat
       && TREE_CODE (decl) == VAR_DECL
-      && TREE_READONLY (decl)
       && !DECL_EXTERNAL (decl)
       && DECL_INITIAL (decl) == NULL_TREE)
-    warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wc___compat,
-		"uninitialized const %qD is invalid in C++", decl);
+    {
+      if (TREE_READONLY (decl))
+	warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wc___compat,
+		    "uninitialized const %qD is invalid in C++", decl);
+      else if (TREE_CODE (type) == RECORD_TYPE
+	       || TREE_CODE (type) == UNION_TYPE)
+	diagnose_uninitialized_cst_member (decl, type);
+    }
 }
 
 /* Given a parsed parameter declaration, decode it into a PARM_DECL.  */
Index: testsuite/gcc.dg/Wcxx-compat-20.c
===================================================================
--- testsuite/gcc.dg/Wcxx-compat-20.c	(revision 0)
+++ testsuite/gcc.dg/Wcxx-compat-20.c	(revision 0)
@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+/* { dg-options "-Wc++-compat" } */
+typedef struct s { const int i; } s; /* { dg-message "should be initialized" } */
+void foo () { s v; } /* { dg-warning "uninitialized const member in" } */
+
+union u {const int a; double b;}; /* { dg-message "should be initialized" } */
+void bar () { union u f; } /* { dg-warning "uninitialized const member in" } */