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-rw-r--r--gcc/ChangeLog5
-rw-r--r--gcc/c-family/ChangeLog5
-rw-r--r--gcc/c-family/c.opt4
-rw-r--r--gcc/cp/ChangeLog12
-rw-r--r--gcc/cp/cp-tree.h5
-rw-r--r--gcc/cp/pt.c21
-rw-r--r--gcc/cp/rtti.c11
-rw-r--r--gcc/cp/tree.c11
-rw-r--r--gcc/cp/typeck.c55
-rw-r--r--gcc/doc/invoke.texi9
-rw-r--r--gcc/testsuite/g++.dg/warn/Wuseless-cast.C123
11 files changed, 241 insertions, 20 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 670361eb04a..050d379891d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2012-03-19 Paolo Carlini <paolo.carlini@oracle.com>
+
+ PR c++/14710
+ * doc/invoke.texi: Document -Wuseless-cast.
+
2012-03-19 Eric Botcazou <ebotcazou@adacore.com>
* tree.def (REALPART_EXPR, IMAGPART_EXPR, VIEW_CONVERT_EXPR): Move.
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index dd7b77b355a..1b586e505b9 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,8 @@
+2012-03-19 Paolo Carlini <paolo.carlini@oracle.com>
+
+ PR c++/14710
+ * c.opt ([Wuseless-cast]): Add.
+
2012-03-16 Richard Guenther <rguenther@suse.de>
* c-pretty-print.c (pp_c_initializer_list): Adjust.
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index a14514adf2e..1ec5504d5e4 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -697,6 +697,10 @@ Wzero-as-null-pointer-constant
C++ ObjC++ Var(warn_zero_as_null_pointer_constant) Warning
Warn when a literal '0' is used as null pointer
+Wuseless-cast
+C++ ObjC++ Var(warn_useless_cast) Warning
+Warn about useless casts
+
ansi
C ObjC C++ ObjC++
A synonym for -std=c89 (for C) or -std=c++98 (for C++)
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index cf4d453597f..7908bb32775 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,15 @@
+2012-03-19 Paolo Carlini <paolo.carlini@oracle.com>
+
+ PR c++/14710
+ * cp-tree.h (xvalue_p, maybe_warn_about_useless_cast): Declare.
+ * tree.c (xvalue_p): Define.
+ * typeck.c (maybe_warn_about_useless_cast): Define.
+ (build_reinterpret_cast, build_const_cast,
+ build_static_cast, cp_build_c_cast): Use maybe_warn_about_useless_cast.
+ * rtti.c (build_dynamic_cast): Likewise.
+ * pt.c (tsubst_copy_and_build, case CAST_EXPR): Increment/decrement
+ c_inhibit_evaluation_warnings before/after the build_* calls.
+
2012-03-15 Jason Merrill <jason@redhat.com>
PR c++/52582
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index d24c5961f27..fc60d860108 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1,6 +1,7 @@
/* Definitions for C++ parsing and type checking.
Copyright (C) 1987, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
- 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
+ 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,
+ 2012
Free Software Foundation, Inc.
Contributed by Michael Tiemann (tiemann@cygnus.com)
@@ -5661,6 +5662,7 @@ extern int member_p (const_tree);
extern cp_lvalue_kind real_lvalue_p (const_tree);
extern cp_lvalue_kind lvalue_kind (const_tree);
extern bool lvalue_or_rvalue_with_address_p (const_tree);
+extern bool xvalue_p (const_tree);
extern bool builtin_valid_in_constant_expr_p (const_tree);
extern tree build_min (enum tree_code, tree, ...);
extern tree build_min_nt (enum tree_code, ...);
@@ -5860,6 +5862,7 @@ extern int lvalue_or_else (tree, enum lvalue_use,
extern void check_template_keyword (tree);
extern bool check_raw_literal_operator (const_tree decl);
extern bool check_literal_operator_args (const_tree, bool *, bool *);
+extern void maybe_warn_about_useless_cast (tree, tree, tsubst_flags_t);
/* in typeck2.c */
extern void require_complete_eh_spec_types (tree, tree);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6dd004e632d..b36e49d4a07 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -13444,7 +13444,7 @@ tsubst_copy_and_build (tree t,
case STATIC_CAST_EXPR:
{
tree type;
- tree op;
+ tree op, r = NULL_TREE;
type = tsubst (TREE_TYPE (t), args, complain, in_decl);
if (integral_constant_expression_p
@@ -13458,21 +13458,30 @@ tsubst_copy_and_build (tree t,
op = RECUR (TREE_OPERAND (t, 0));
+ ++c_inhibit_evaluation_warnings;
switch (TREE_CODE (t))
{
case CAST_EXPR:
- return build_functional_cast (type, op, complain);
+ r = build_functional_cast (type, op, complain);
+ break;
case REINTERPRET_CAST_EXPR:
- return build_reinterpret_cast (type, op, complain);
+ r = build_reinterpret_cast (type, op, complain);
+ break;
case CONST_CAST_EXPR:
- return build_const_cast (type, op, complain);
+ r = build_const_cast (type, op, complain);
+ break;
case DYNAMIC_CAST_EXPR:
- return build_dynamic_cast (type, op, complain);
+ r = build_dynamic_cast (type, op, complain);
+ break;
case STATIC_CAST_EXPR:
- return build_static_cast (type, op, complain);
+ r = build_static_cast (type, op, complain);
+ break;
default:
gcc_unreachable ();
}
+ --c_inhibit_evaluation_warnings;
+
+ return r;
}
case POSTDECREMENT_EXPR:
diff --git a/gcc/cp/rtti.c b/gcc/cp/rtti.c
index 30383ed18ad..2ca8fa511fa 100644
--- a/gcc/cp/rtti.c
+++ b/gcc/cp/rtti.c
@@ -1,6 +1,6 @@
/* RunTime Type Identification
Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
- 2005, 2006, 2007, 2008, 2009, 2010, 2011
+ 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
Free Software Foundation, Inc.
Mostly written by Jason Merrill (jason@cygnus.com).
@@ -774,6 +774,8 @@ build_dynamic_cast_1 (tree type, tree expr, tsubst_flags_t complain)
tree
build_dynamic_cast (tree type, tree expr, tsubst_flags_t complain)
{
+ tree r;
+
if (type == error_mark_node || expr == error_mark_node)
return error_mark_node;
@@ -784,9 +786,12 @@ build_dynamic_cast (tree type, tree expr, tsubst_flags_t complain)
return convert_from_reference (expr);
}
- return convert_from_reference (build_dynamic_cast_1 (type, expr, complain));
+ r = convert_from_reference (build_dynamic_cast_1 (type, expr, complain));
+ if (r != error_mark_node)
+ maybe_warn_about_useless_cast (type, expr, complain);
+ return r;
}
-
+
/* Return the runtime bit mask encoding the qualifiers of TYPE. */
static int
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index b80b52a8e50..87e9be84ecc 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -1,6 +1,7 @@
/* Language-dependent node constructors for parse phase of GNU compiler.
Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
- 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011
+ 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011,
+ 2012
Free Software Foundation, Inc.
Hacked by Michael Tiemann (tiemann@cygnus.com)
@@ -274,6 +275,14 @@ lvalue_or_rvalue_with_address_p (const_tree ref)
return (kind != clk_none);
}
+/* Returns true if REF is an xvalue, false otherwise. */
+
+bool
+xvalue_p (const_tree ref)
+{
+ return (lvalue_kind (ref) == clk_rvalueref);
+}
+
/* Test whether DECL is a builtin that may appear in a
constant-expression. */
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 643454cf227..d2d6c4ef049 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -5749,6 +5749,28 @@ check_for_casting_away_constness (tree src_type, tree dest_type,
}
}
+/*
+ Warns if the cast from expression EXPR to type TYPE is useless.
+ */
+void
+maybe_warn_about_useless_cast (tree type, tree expr, tsubst_flags_t complain)
+{
+ if (warn_useless_cast
+ && complain & tf_warning
+ && c_inhibit_evaluation_warnings == 0)
+ {
+ if (REFERENCE_REF_P (expr))
+ expr = TREE_OPERAND (expr, 0);
+
+ if ((TREE_CODE (type) == REFERENCE_TYPE
+ && (TYPE_REF_IS_RVALUE (type)
+ ? xvalue_p (expr) : real_lvalue_p (expr))
+ && same_type_p (TREE_TYPE (expr), TREE_TYPE (type)))
+ || same_type_p (TREE_TYPE (expr), type))
+ warning (OPT_Wuseless_cast, "useless cast to type %qT", type);
+ }
+}
+
/* Convert EXPR (an expression with pointer-to-member type) to TYPE
(another pointer-to-member type in the same hierarchy) and return
the converted expression. If ALLOW_INVERSE_P is permitted, a
@@ -6078,7 +6100,11 @@ build_static_cast (tree type, tree expr, tsubst_flags_t complain)
result = build_static_cast_1 (type, expr, /*c_cast_p=*/false, &valid_p,
complain);
if (valid_p)
- return result;
+ {
+ if (result != error_mark_node)
+ maybe_warn_about_useless_cast (type, expr, complain);
+ return result;
+ }
if (complain & tf_error)
error ("invalid static_cast from type %qT to type %qT",
@@ -6305,6 +6331,8 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
tree
build_reinterpret_cast (tree type, tree expr, tsubst_flags_t complain)
{
+ tree r;
+
if (type == error_mark_node || expr == error_mark_node)
return error_mark_node;
@@ -6319,8 +6347,11 @@ build_reinterpret_cast (tree type, tree expr, tsubst_flags_t complain)
return convert_from_reference (t);
}
- return build_reinterpret_cast_1 (type, expr, /*c_cast_p=*/false,
- /*valid_p=*/NULL, complain);
+ r = build_reinterpret_cast_1 (type, expr, /*c_cast_p=*/false,
+ /*valid_p=*/NULL, complain);
+ if (r != error_mark_node)
+ maybe_warn_about_useless_cast (type, expr, complain);
+ return r;
}
/* Perform a const_cast from EXPR to TYPE. If the cast is valid,
@@ -6464,6 +6495,8 @@ build_const_cast_1 (tree dst_type, tree expr, tsubst_flags_t complain,
tree
build_const_cast (tree type, tree expr, tsubst_flags_t complain)
{
+ tree r;
+
if (type == error_mark_node || error_operand_p (expr))
return error_mark_node;
@@ -6478,8 +6511,10 @@ build_const_cast (tree type, tree expr, tsubst_flags_t complain)
return convert_from_reference (t);
}
- return build_const_cast_1 (type, expr, complain,
- /*valid_p=*/NULL);
+ r = build_const_cast_1 (type, expr, complain, /*valid_p=*/NULL);
+ if (r != error_mark_node)
+ maybe_warn_about_useless_cast (type, expr, complain);
+ return r;
}
/* Like cp_build_c_cast, but for the c-common bits. */
@@ -6567,7 +6602,11 @@ cp_build_c_cast (tree type, tree expr, tsubst_flags_t complain)
result = build_const_cast_1 (type, value, complain & tf_warning,
&valid_p);
if (valid_p)
- return result;
+ {
+ if (result != error_mark_node)
+ maybe_warn_about_useless_cast (type, value, complain);
+ return result;
+ }
/* Or a static cast. */
result = build_static_cast_1 (type, value, /*c_cast_p=*/true,
@@ -6580,11 +6619,13 @@ cp_build_c_cast (tree type, tree expr, tsubst_flags_t complain)
const_cast. */
if (valid_p
/* A valid cast may result in errors if, for example, a
- conversion to am ambiguous base class is required. */
+ conversion to an ambiguous base class is required. */
&& !error_operand_p (result))
{
tree result_type;
+ maybe_warn_about_useless_cast (type, value, complain);
+
/* Non-class rvalues always have cv-unqualified type. */
if (!CLASS_TYPE_P (type))
type = TYPE_MAIN_VARIANT (type);
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 8571a8bca89..bf821ff97e5 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -274,8 +274,8 @@ Objective-C and Objective-C++ Dialects}.
-Wunused-label -Wunused-local-typedefs -Wunused-parameter @gol
-Wno-unused-result -Wunused-value @gol -Wunused-variable @gol
-Wunused-but-set-parameter -Wunused-but-set-variable @gol
--Wvariadic-macros -Wvector-operation-performance -Wvla
--Wvolatile-register-var -Wwrite-strings -Wzero-as-null-pointer-constant}
+-Wuseless-cast -Wvariadic-macros -Wvector-operation-performance @gol
+-Wvla -Wvolatile-register-var -Wwrite-strings -Wzero-as-null-pointer-constant}
@item C and Objective-C-only Warning Options
@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol
@@ -4199,6 +4199,11 @@ types. @option{-Wconversion-null} is enabled by default.
Warn when a literal '0' is used as null pointer constant. This can
be useful to facilitate the conversion to @code{nullptr} in C++11.
+@item -Wuseless-cast @r{(C++ and Objective-C++ only)}
+@opindex Wuseless-cast
+@opindex Wno-useless-cast
+Warn when an expression is casted to its own type.
+
@item -Wempty-body
@opindex Wempty-body
@opindex Wno-empty-body
diff --git a/gcc/testsuite/g++.dg/warn/Wuseless-cast.C b/gcc/testsuite/g++.dg/warn/Wuseless-cast.C
new file mode 100644
index 00000000000..8000d93db9c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wuseless-cast.C
@@ -0,0 +1,123 @@
+// { dg-options "-Wuseless-cast" }
+
+template<typename T>
+ void tmpl_f1(T& t)
+ {
+ (int)(t);
+ static_cast<int>(t);
+ reinterpret_cast<int>(t);
+
+ (int*)(&t);
+ const_cast<int*>(&t);
+ static_cast<int*>(&t);
+ reinterpret_cast<int*>(&t);
+
+ (int&)(t);
+ const_cast<int&>(t);
+ static_cast<int&>(t);
+ reinterpret_cast<int&>(t);
+ }
+
+template<typename T>
+ void tmpl_f2(T t)
+ {
+ (int&)(t);
+ const_cast<int&>(t);
+ static_cast<int&>(t);
+ reinterpret_cast<int&>(t);
+ }
+
+struct A { };
+
+template<typename T>
+ void tmpl_f3(T& t)
+ {
+ (A)(t);
+ static_cast<A>(t);
+
+ (A*)(&t);
+ const_cast<A*>(&t);
+ static_cast<A*>(&t);
+ reinterpret_cast<A*>(&t);
+ dynamic_cast<A*>(&t);
+
+ (A&)(t);
+ const_cast<A&>(t);
+ static_cast<A&>(t);
+ reinterpret_cast<A&>(t);
+ dynamic_cast<A&>(t);
+ }
+
+template<typename T>
+ void tmpl_f4(T t)
+ {
+ (A&)(t);
+ const_cast<A&>(t);
+ static_cast<A&>(t);
+ reinterpret_cast<A&>(t);
+ dynamic_cast<A&>(t);
+ }
+
+void f()
+{
+ int n;
+
+ (int)(n); // { dg-warning "useless cast" }
+ static_cast<int>(n); // { dg-warning "useless cast" }
+ reinterpret_cast<int>(n); // { dg-warning "useless cast" }
+
+ (int*)(&n); // { dg-warning "useless cast" }
+ const_cast<int*>(&n); // { dg-warning "useless cast" }
+ static_cast<int*>(&n); // { dg-warning "useless cast" }
+ reinterpret_cast<int*>(&n); // { dg-warning "useless cast" }
+
+ int& m = n;
+
+ (int&)(m); // { dg-warning "useless cast" }
+ const_cast<int&>(m); // { dg-warning "useless cast" }
+ static_cast<int&>(m); // { dg-warning "useless cast" }
+ reinterpret_cast<int&>(m); // { dg-warning "useless cast" }
+
+ tmpl_f1(m);
+
+ (int&)(n); // { dg-warning "useless cast" }
+ const_cast<int&>(n); // { dg-warning "useless cast" }
+ static_cast<int&>(n); // { dg-warning "useless cast" }
+ reinterpret_cast<int&>(n); // { dg-warning "useless cast" }
+
+ tmpl_f2(n);
+
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+ (int&&)(42);
+ static_cast<int&&>(42);
+#endif
+
+ A a;
+
+ (A)(a); // { dg-warning "useless cast" }
+ static_cast<A>(a); // { dg-warning "useless cast" }
+
+ (A*)(&a); // { dg-warning "useless cast" }
+ const_cast<A*>(&a); // { dg-warning "useless cast" }
+ static_cast<A*>(&a); // { dg-warning "useless cast" }
+ reinterpret_cast<A*>(&a); // { dg-warning "useless cast" }
+ dynamic_cast<A*>(&a); // { dg-warning "useless cast" }
+
+ A& b = a;
+
+ (A&)(b); // { dg-warning "useless cast" }
+ const_cast<A&>(b); // { dg-warning "useless cast" }
+ static_cast<A&>(b); // { dg-warning "useless cast" }
+ static_cast<A&>(b); // { dg-warning "useless cast" }
+ dynamic_cast<A&>(b); // { dg-warning "useless cast" }
+
+ tmpl_f3(b);
+
+ (A&)(a); // { dg-warning "useless cast" }
+ const_cast<A&>(a); // { dg-warning "useless cast" }
+ static_cast<A&>(a); // { dg-warning "useless cast" }
+ reinterpret_cast<A&>(a); // { dg-warning "useless cast" }
+ dynamic_cast<A&>(a); // { dg-warning "useless cast" }
+
+ tmpl_f4(a);
+}
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