===================================================================
@@ -6064,6 +6064,53 @@ S *p = (S *)malloc (sizeof(S) + 100);
p->data[10] = 0; //OK
@end smallexample
+@item scalar_storage_order
+@itemx scalar_storage_order ("@var{endianness}")
+@cindex @code{scalar_storage_order} type attribute
+When attached to a @code{union} or a @code{struct}, this attribute sets
+the storage order, aka endianness, of the scalar fields of the type, as
+well as the array fields whose component is scalar. The supported
+endianness are @code{big-endian} and @code{little-endian}. The attribute
+has no effects on fields which are themselves a @code{union}, a @code{struct}
+or an array whose component is a @code{union} or a @code{struct}, and it is
+possible to have fields with a different scalar storage order than the
+enclosing type.
+
+This attribute is supported only for targets that use a uniform default
+scalar storage order (fortunately, most of them), i.e. targets that store
+the scalars either all in big-endian or all in little-endian.
+
+Additional restrictions are enforced for types with the reverse scalar
+storage order with regard to the scalar storage order of the target:
+
+@itemize
+@item Taking the address of a scalar field of a @code{union} or a
+@code{struct} with reverse scalar storage order is illegal and will
+yield an error
+@item Taking the address of an array field, whose component is scalar, of
+a @code{union} or a @code{struct} with reverse scalar storage order is
+permitted but will yield a warning, unless @option{-Wno-scalar-storage-order}
+is specified
+@item Taking the address of a @code{union} or a @code{struct} with reverse
+scalar storage order is permitted
+@end itemize
+
+These restrictions exist because the storage order attribute is lost when
+the address of a scalar or the address of an array with scalar component
+is taken, so storing indirectly through this address will generally not work.
+The second case is nevertheless allowed to be able to perform a block copy
+from or to the array.
+
+@item unused
+@cindex @code{unused} type attribute
+When attached to a type (including a @code{union} or a @code{struct}),
+this attribute means that variables of that type are meant to appear
+possibly unused. GCC does not produce a warning for any variables of
+that type, even if the variable appears to do nothing. This is often
+the case with lock or thread classes, which are usually defined and then
+not referenced, but contain constructors and destructors that have
+nontrivial bookkeeping functions.
+
@item deprecated
@itemx deprecated (@var{msg})
@cindex @code{deprecated} type attribute
===================================================================
@@ -275,6 +275,7 @@ Objective-C and Objective-C++ Dialects}.
-Wreturn-type -Wsequence-point -Wshadow -Wno-shadow-ivar @gol
-Wshift-count-negative -Wshift-count-overflow -Wshift-negative-value @gol
-Wsign-compare -Wsign-conversion -Wfloat-conversion @gol
+-Wno-scalar-storage-order @gol
-Wsizeof-pointer-memaccess -Wsizeof-array-argument @gol
-Wstack-protector -Wstack-usage=@var{len} -Wstrict-aliasing @gol
-Wstrict-aliasing=n @gol -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
@@ -4938,6 +4939,11 @@ This includes conversions from real to i
real to lower precision real values. This option is also enabled by
@option{-Wconversion}.
+@item -Wno-scalar-storage-order
+@opindex -Wno-scalar-storage-order
+@opindex -Wscalar-storage-order
+Do not warn on suspicious constructs involving reverse scalar storage order.
+
@item -Wsized-deallocation @r{(C++ and Objective-C++ only)}
@opindex Wsized-deallocation
@opindex Wno-sized-deallocation
===================================================================
@@ -768,6 +768,10 @@ Wreturn-type
C ObjC C++ ObjC++ Var(warn_return_type) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
Warn whenever a function's return type defaults to \"int\" (C), or about inconsistent return types (C++)
+Wscalar-storage-order
+C ObjC C++ ObjC++ Init(1) Warning
+Warn on suspicious constructs involving reverse scalar storage order
+
Wselector
ObjC ObjC++ Var(warn_selector) Warning
Warn if a selector has multiple methods
===================================================================
@@ -346,6 +346,8 @@ static tree handle_no_reorder_attribute
static tree handle_const_attribute (tree *, tree, tree, int, bool *);
static tree handle_transparent_union_attribute (tree *, tree, tree,
int, bool *);
+static tree handle_scalar_storage_order_attribute (tree *, tree, tree,
+ int, bool *);
static tree handle_constructor_attribute (tree *, tree, tree, int, bool *);
static tree handle_destructor_attribute (tree *, tree, tree, int, bool *);
static tree handle_mode_attribute (tree *, tree, tree, int, bool *);
@@ -690,6 +692,8 @@ const struct attribute_spec c_common_att
handle_const_attribute, false },
{ "transparent_union", 0, 0, false, false, false,
handle_transparent_union_attribute, false },
+ { "scalar_storage_order", 1, 1, false, false, false,
+ handle_scalar_storage_order_attribute, false },
{ "constructor", 0, 1, true, false, false,
handle_constructor_attribute, false },
{ "destructor", 0, 1, true, false, false,
@@ -7502,7 +7506,6 @@ handle_transparent_union_attribute (tree
*no_add_attrs = true;
-
if (TREE_CODE (*node) == TYPE_DECL
&& ! (flags & ATTR_FLAG_CXX11))
node = &TREE_TYPE (*node);
@@ -7542,6 +7545,55 @@ handle_transparent_union_attribute (tree
return NULL_TREE;
}
+ ignored:
+ warning (OPT_Wattributes, "%qE attribute ignored", name);
+ return NULL_TREE;
+}
+
+/* Handle a "scalar_storage_order" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_scalar_storage_order_attribute (tree *node, tree name, tree args,
+ int flags, bool *no_add_attrs)
+{
+ tree id = TREE_VALUE (args);
+ tree type;
+
+ *no_add_attrs = true;
+
+ if (TREE_CODE (*node) == TYPE_DECL
+ && ! (flags & ATTR_FLAG_CXX11))
+ node = &TREE_TYPE (*node);
+ type = *node;
+
+ if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN)
+ error ("scalar_storage_order is not supported");
+
+ if (RECORD_OR_UNION_TYPE_P (type))
+ {
+ if (!(flags & (int) ATTR_FLAG_TYPE_IN_PLACE))
+ goto ignored;
+
+ if (TREE_CODE (id) == STRING_CST
+ && strcmp (TREE_STRING_POINTER (id), "big-endian") == 0)
+ {
+ if (!BYTES_BIG_ENDIAN)
+ TYPE_REVERSE_STORAGE_ORDER (type) = 1;
+ }
+ else if (TREE_CODE (id) == STRING_CST
+ && strcmp (TREE_STRING_POINTER (id), "little-endian") == 0)
+ {
+ if (BYTES_BIG_ENDIAN)
+ TYPE_REVERSE_STORAGE_ORDER (type) = 1;
+ }
+ else
+ error ("scalar_storage_order argument must be one of \"big-endian\" "
+ "or \"little-endian\"");
+
+ return NULL_TREE;
+ }
+
ignored:
warning (OPT_Wattributes, "%qE attribute ignored", name);
return NULL_TREE;
===================================================================
@@ -4163,18 +4163,10 @@ build_unary_op (location_t location,
goto return_build_unary_op;
}
- /* For &x[y], return x+y */
- if (TREE_CODE (arg) == ARRAY_REF)
- {
- tree op0 = TREE_OPERAND (arg, 0);
- if (!c_mark_addressable (op0))
- return error_mark_node;
- }
-
/* Anything not already handled and not a true memory reference
or a non-lvalue array is an error. */
- else if (typecode != FUNCTION_TYPE && !flag
- && !lvalue_or_else (location, arg, lv_addressof))
+ if (typecode != FUNCTION_TYPE && !flag
+ && !lvalue_or_else (location, arg, lv_addressof))
return error_mark_node;
/* Move address operations inside C_MAYBE_CONST_EXPR to simplify
@@ -4212,6 +4204,38 @@ build_unary_op (location_t location,
argtype = c_build_qualified_type (argtype, quals);
}
+ switch (TREE_CODE (arg))
+ {
+ case COMPONENT_REF:
+ if (DECL_C_BIT_FIELD (TREE_OPERAND (arg, 1)))
+ {
+ error ("cannot take address of bit-field %qD",
+ TREE_OPERAND (arg, 1));
+ return error_mark_node;
+ }
+
+ /* ... fall through ... */
+
+ case ARRAY_REF:
+ if (TYPE_REVERSE_STORAGE_ORDER (TREE_TYPE (TREE_OPERAND (arg, 0))))
+ {
+ if (!AGGREGATE_TYPE_P (TREE_TYPE (arg)))
+ {
+ error ("cannot take address of scalar with reverse storage "
+ "order");
+ return error_mark_node;
+ }
+
+ if (TREE_CODE (TREE_TYPE (arg)) == ARRAY_TYPE
+ && TYPE_REVERSE_STORAGE_ORDER (TREE_TYPE (arg)))
+ warning (OPT_Wscalar_storage_order, "address of array with "
+ "reverse scalar storage order requested");
+ }
+
+ default:
+ break;
+ }
+
if (!c_mark_addressable (arg))
return error_mark_node;
@@ -4354,15 +4378,6 @@ c_mark_addressable (tree exp)
switch (TREE_CODE (x))
{
case COMPONENT_REF:
- if (DECL_C_BIT_FIELD (TREE_OPERAND (x, 1)))
- {
- error
- ("cannot take address of bit-field %qD", TREE_OPERAND (x, 1));
- return false;
- }
-
- /* ... fall through ... */
-
case ADDR_EXPR:
case ARRAY_REF:
case REALPART_EXPR:
===================================================================
@@ -7732,27 +7732,44 @@ finish_struct (location_t loc, tree t, t
&& !valid_constant_size_p (TYPE_SIZE_UNIT (t)))
error ("type %qT is too large", t);
- /* Give bit-fields their proper types. */
- {
- tree *fieldlistp = &fieldlist;
- while (*fieldlistp)
- if (TREE_CODE (*fieldlistp) == FIELD_DECL && DECL_INITIAL (*fieldlistp)
- && TREE_TYPE (*fieldlistp) != error_mark_node)
+ /* Give bit-fields their proper types and rewrite the type of array fields
+ if the enclosing type has reverse storage order. */
+ for (tree field = fieldlist; field; field = DECL_CHAIN (field))
+ {
+ if (TREE_CODE (field) == FIELD_DECL
+ && DECL_INITIAL (field)
+ && TREE_TYPE (field) != error_mark_node)
{
unsigned HOST_WIDE_INT width
- = tree_to_uhwi (DECL_INITIAL (*fieldlistp));
- tree type = TREE_TYPE (*fieldlistp);
+ = tree_to_uhwi (DECL_INITIAL (field));
+ tree type = TREE_TYPE (field);
if (width != TYPE_PRECISION (type))
{
- TREE_TYPE (*fieldlistp)
+ TREE_TYPE (field)
= c_build_bitfield_integer_type (width, TYPE_UNSIGNED (type));
- DECL_MODE (*fieldlistp) = TYPE_MODE (TREE_TYPE (*fieldlistp));
+ DECL_MODE (field) = TYPE_MODE (TREE_TYPE (field));
}
- DECL_INITIAL (*fieldlistp) = 0;
+ DECL_INITIAL (field) = 0;
}
- else
- fieldlistp = &DECL_CHAIN (*fieldlistp);
- }
+ else if (TYPE_REVERSE_STORAGE_ORDER (t)
+ && TREE_CODE (field) == FIELD_DECL
+ && TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE)
+ {
+ tree ftype = TREE_TYPE (field);
+ do
+ ftype = TREE_TYPE (ftype);
+ while (TREE_CODE (ftype) == ARRAY_TYPE);
+ if (!RECORD_OR_UNION_TYPE_P (ftype))
+ {
+ tree *ftypep = &TREE_TYPE (field);
+ do {
+ *ftypep = build_distinct_type_copy (*ftypep);
+ TYPE_REVERSE_STORAGE_ORDER (*ftypep) = 1;
+ ftypep = &TREE_TYPE (*ftypep);
+ } while (TREE_CODE (*ftypep) == ARRAY_TYPE);
+ }
+ }
+ }
/* Now we have the truly final field list.
Store it in this type and in the variants. */