re PR c++/38980 (missing -Wformat warning on const char format string)

/cp
2011-10-09  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/38980
	* init.c (constant_value_1): Add bool parameter.
	(decl_constant_value_safe): Add.
	(integral_constant_value): Adjust.
	(decl_constant_value): Adjust.
	* cp-tree.h (decl_constant_value_safe): Declare.
	* typeck.c (decay_conversion): Use decl_constant_value_safe.
	* call.c (convert_like_real): Likewise.

/testsuite
2011-10-09  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/38980
	* g++.dg/warn/format5.C: New.

From-SVN: r179731

7 files changed, 57 insertions, 16 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index d520bda..c27d8a6 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,14 @@
+2011-10-09  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/38980
+	* init.c (constant_value_1): Add bool parameter.
+	(decl_constant_value_safe): Add.
+	(integral_constant_value): Adjust.
+	(decl_constant_value): Adjust.
+	* cp-tree.h (decl_constant_value_safe): Declare.
+	* typeck.c (decay_conversion): Use decl_constant_value_safe.
+	* call.c (convert_like_real): Likewise.
+
 2011-10-09  Jakub Jelinek  <jakub@redhat.com>
 	    Diego Novillo  <dnovillo@google.com>
 
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index a52ec29..ee71d9b 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -5703,7 +5703,7 @@ convert_like_real (conversion *convs, tree expr, tree fn, int argnum,
 	 leave it as an lvalue.  */
       if (inner >= 0)
         {   
-          expr = decl_constant_value (expr);
+          expr = decl_constant_value_safe (expr);
           if (expr == null_node && INTEGRAL_OR_UNSCOPED_ENUMERATION_TYPE_P (totype))
             /* If __null has been converted to an integer type, we do not
                want to warn about uses of EXPR as an integer, rather than
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 7e5aac7..f824f38 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -5097,6 +5097,7 @@ extern tree create_temporary_var		(tree);
 extern void initialize_vtbl_ptrs		(tree);
 extern tree build_java_class_ref		(tree);
 extern tree integral_constant_value		(tree);
+extern tree decl_constant_value_safe	        (tree);
 extern int diagnose_uninitialized_cst_or_ref_member (tree, bool, bool);
 
 /* in lex.c */
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index f246286..7897fff 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -1794,10 +1794,11 @@ build_offset_ref (tree type, tree member, bool address_p)
    constant initializer, return the initializer (or, its initializers,
    recursively); otherwise, return DECL.  If INTEGRAL_P, the
    initializer is only returned if DECL is an integral
-   constant-expression.  */
+   constant-expression.  If RETURN_AGGREGATE_CST_OK_P, it is ok to
+   return an aggregate constant.  */
 
 static tree
-constant_value_1 (tree decl, bool integral_p)
+constant_value_1 (tree decl, bool integral_p, bool return_aggregate_cst_ok_p)
 {
   while (TREE_CODE (decl) == CONST_DECL
 	 || (integral_p
@@ -1834,12 +1835,13 @@ constant_value_1 (tree decl, bool integral_p)
       if (!init
 	  || !TREE_TYPE (init)
 	  || !TREE_CONSTANT (init)
-	  || (!integral_p
-	      /* Do not return an aggregate constant (of which
-		 string literals are a special case), as we do not
-		 want to make inadvertent copies of such entities,
-		 and we must be sure that their addresses are the
-		 same everywhere.  */
+	  || (!integral_p && !return_aggregate_cst_ok_p
+	      /* Unless RETURN_AGGREGATE_CST_OK_P is true, do not
+		 return an aggregate constant (of which string
+		 literals are a special case), as we do not want
+		 to make inadvertent copies of such entities, and
+		 we must be sure that their addresses are the
+ 		 same everywhere.  */
 	      && (TREE_CODE (init) == CONSTRUCTOR
 		  || TREE_CODE (init) == STRING_CST)))
 	break;
@@ -1856,18 +1858,28 @@ constant_value_1 (tree decl, bool integral_p)
 tree
 integral_constant_value (tree decl)
 {
-  return constant_value_1 (decl, /*integral_p=*/true);
+  return constant_value_1 (decl, /*integral_p=*/true,
+			   /*return_aggregate_cst_ok_p=*/false);
 }
 
 /* A more relaxed version of integral_constant_value, used by the
-   common C/C++ code and by the C++ front end for optimization
-   purposes.  */
+   common C/C++ code.  */
 
 tree
 decl_constant_value (tree decl)
 {
-  return constant_value_1 (decl,
-			   /*integral_p=*/processing_template_decl);
+  return constant_value_1 (decl, /*integral_p=*/processing_template_decl,
+			   /*return_aggregate_cst_ok_p=*/true);
+}
+
+/* A version of integral_constant_value used by the C++ front end for
+   optimization purposes.  */
+
+tree
+decl_constant_value_safe (tree decl)
+{
+  return constant_value_1 (decl, /*integral_p=*/processing_template_decl,
+			   /*return_aggregate_cst_ok_p=*/false);
 }
 
 /* Common subroutines of build_new and build_vec_delete.  */
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index d416b42..305f8f5 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -1827,7 +1827,7 @@ decay_conversion (tree exp)
   /* FIXME remove? at least need to remember that this isn't really a
      constant expression if EXP isn't decl_constant_var_p, like with
      C_MAYBE_CONST_EXPR.  */
-  exp = decl_constant_value (exp);
+  exp = decl_constant_value_safe (exp);
   if (error_operand_p (exp))
     return error_mark_node;
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index bef6c34..d3be034 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-10-09  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/38980
+	* g++.dg/warn/format5.C: New.
+
 2011-10-09  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/45044
@@ -22,7 +27,7 @@
 
 2011-10-08  Nicola Pero  <nicola.pero@meta-innovation.com>
 
-	PR libobjc/50428	
+	PR libobjc/50428
 	* objc/execute/initialize-1.m: New test.
 
 2011-10-08  Paul Thomas  <pault@gcc.gnu.org>
diff --git a/gcc/testsuite/g++.dg/warn/format5.C b/gcc/testsuite/g++.dg/warn/format5.C
new file mode 100644
index 0000000..e219f88
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/format5.C
@@ -0,0 +1,12 @@
+// PR c++/38980
+// { dg-options "-Wformat" }
+
+extern "C"
+int printf(const char *format, ...) __attribute__((format(printf, 1, 2) ));
+
+const char fmt1[] = "Hello, %s";
+
+void f()
+{
+  printf(fmt1, 3); // { dg-warning "expects argument" }
+}