LEVEL=0 is the least strict level, all trailing arrays of
structures are treated as flexible array members. LEVEL=3 is the
strictest level, only when the trailing array is declared as a
flexible array member per C99 standard onwards ('[]'), it is
treated as a flexible array member.
There are two more levels in between 0 and 3, which are provided to
support older codes that use GCC zero-length array extension
('[0]') or one-size array as flexible array member ('[1]'): When
LEVEL is 1, the trailing array is treated as a flexible array
member when it is declared as either '[]', '[0]', or '[1]'; When
LEVEL is 2, the trailing array is treated as a flexible array
member when it is declared as either '[]', or '[0]'.
This attribute can be used with or without the
'-fstrict-flex-arrays'. When both the attribute and the option
present at the same time, the level of the strictness for the
specific trailing array field is determined by the attribute.
gcc/c-family/ChangeLog:
* c-attribs.cc (handle_strict_flex_arrays_attribute): New function.
(c_common_attribute_table): New item for strict_flex_arrays.
* c.opt: (fstrict-flex-arrays): New option.
(fstrict-flex-arrays=): New option.
gcc/c/ChangeLog:
* c-decl.cc (flexible_array_member_type_p): New function.
(one_element_array_type_p): Likewise.
(zero_length_array_type_p): Likewise.
(add_flexible_array_elts_to_size): Call new utility
routine flexible_array_member_type_p.
(is_flexible_array_member_p): New function.
(finish_struct): Set the new DECL_NOT_FLEXARRAY flag.
gcc/cp/ChangeLog:
* module.cc (trees_out::core_bools): Stream out new bit
decl_not_flexarray.
(trees_in::core_bools): Stream in new bit decl_not_flexarray.
gcc/ChangeLog:
* doc/extend.texi: Document strict_flex_arrays attribute.
* doc/invoke.texi: Document -fstrict-flex-arrays[=n] option.
* print-tree.cc (print_node): Print new bit decl_not_flexarray.
* tree-core.h (struct tree_decl_common): New bit field
decl_not_flexarray.
* tree-streamer-in.cc (unpack_ts_decl_common_value_fields): Stream
in new bit decl_not_flexarray.
* tree-streamer-out.cc (pack_ts_decl_common_value_fields): Stream
out new bit decl_not_flexarray.
* tree.cc (array_at_struct_end_p): Update it with the new bit field
decl_not_flexarray.
* tree.h (DECL_NOT_FLEXARRAY): New flag.
gcc/testsuite/ChangeLog:
* g++.dg/strict-flex-array-1.C: New test.
* gcc.dg/strict-flex-array-1.c: New test.
---
gcc/c-family/c-attribs.cc | 47 ++++++++
gcc/c-family/c.opt | 7 ++
gcc/c/c-decl.cc | 130 +++++++++++++++++++--
gcc/cp/module.cc | 2 +
gcc/doc/extend.texi | 25 ++++
gcc/doc/invoke.texi | 27 ++++-
gcc/print-tree.cc | 8 +-
gcc/testsuite/g++.dg/strict-flex-array-1.C | 31 +++++
gcc/testsuite/gcc.dg/strict-flex-array-1.c | 31 +++++
gcc/tree-core.h | 5 +-
gcc/tree-streamer-in.cc | 1 +
gcc/tree-streamer-out.cc | 1 +
gcc/tree.cc | 45 +++++--
gcc/tree.h | 14 ++-
14 files changed, 346 insertions(+), 28 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/strict-flex-array-1.C
create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-1.c
diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index 8bb80e251dc2..0becd4bbe8d2 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -101,6 +101,8 @@ static tree handle_special_var_sec_attribute (tree *, tree,
tree, int, bool *);
static tree handle_aligned_attribute (tree *, tree, tree, int, bool *);
static tree handle_warn_if_not_aligned_attribute (tree *, tree, tree,
int, bool *);
+static tree handle_strict_flex_arrays_attribute (tree *, tree, tree,
+ int, bool *);
static tree handle_weak_attribute (tree *, tree, tree, int, bool *) ;
static tree handle_noplt_attribute (tree *, tree, tree, int, bool *) ;
static tree handle_alias_ifunc_attribute (bool, tree *, tree, tree, bool *);
@@ -368,6 +370,8 @@ const struct attribute_spec c_common_attribute_table[] =
attr_aligned_exclusions },
{ "warn_if_not_aligned", 0, 1, false, false, false, false,
handle_warn_if_not_aligned_attribute, NULL },
+ { "strict_flex_arrays", 1, 1, false, false, false, false,
+ handle_strict_flex_arrays_attribute, NULL },
{ "weak", 0, 0, true, false, false, false,
handle_weak_attribute, NULL },
{ "noplt", 0, 0, true, false, false, false,
@@ -2505,6 +2509,49 @@ handle_warn_if_not_aligned_attribute (tree *node, tree
name,
no_add_attrs, true);
}
+/* Handle a "strict_flex_arrays" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_strict_flex_arrays_attribute (tree *node, tree name,
+ tree args, int ARG_UNUSED (flags),
+ bool *no_add_attrs)
+{
+ tree decl = *node;
+ tree argval = TREE_VALUE (args);
+
+ /* This attribute only applies to field decls of a structure. */
+ if (TREE_CODE (decl) != FIELD_DECL)
+ {
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "%qE attribute may not be specified for %q+D", name, decl);
+ *no_add_attrs = true;
+ }
+ /* This attribute only applies to field with array type. */
+ else if (TREE_CODE (TREE_TYPE (decl)) != ARRAY_TYPE)
+ {
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "%qE attribute may not be specified for a non-array field",
+ name);
+ *no_add_attrs = true;
+ }
+ else if (TREE_CODE (argval) != INTEGER_CST)
+ {
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "%qE attribute argument not an integer", name);
+ *no_add_attrs = true;
+ }
+ else if (!tree_fits_uhwi_p (argval) || tree_to_uhwi (argval) > 3)
+ {
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "%qE attribute argument %qE is not an integer constant"
+ " between 0 and 3", name, argval);
+ *no_add_attrs = true;
+ }
+
+ return NULL_TREE;
+}
+
/* Handle a "weak" attribute; arguments as in
struct attribute_spec.handler. */
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 4515664aa590..e053bd939559 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -2072,6 +2072,13 @@ fsized-deallocation
C++ ObjC++ Var(flag_sized_deallocation) Init(-1)
Enable C++14 sized deallocation support.
+fstrict-flex-arrays
+C C++ Common Alias(fstrict-flex-arrays=,3,0)
+
+fstrict-flex-arrays=
+C C++ Common Joined RejectNegative UInteger Var(flag_strict_flex_arrays)
Init(0) IntegerRange(0,3)
+-fstrict-flex-arrays=<level> Treat the trailing array of a structure as a
flexible array in a stricter way. The default is treating all trailing arrays of
structures as flexible arrays.
+
fsquangle
C++ ObjC++ WarnRemoved
diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 34f8feda897f..ee90808bcb0e 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -5005,6 +5005,41 @@ set_array_declarator_inner (struct c_declarator *decl,
return decl;
}
+/* Determine whether TYPE is a ISO C99 flexible array memeber type "[]". */
+static bool
+flexible_array_member_type_p (const_tree type)
+{
+ if (TREE_CODE (type) == ARRAY_TYPE
+ && TYPE_SIZE (type) == NULL_TREE
+ && TYPE_DOMAIN (type) != NULL_TREE
+ && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL_TREE)
+ return true;
+
+ return false;
+}
+
+/* Determine whether TYPE is a one-element array type "[1]". */
+static bool
+one_element_array_type_p (const_tree type)
+{
+ if (TREE_CODE (type) != ARRAY_TYPE)
+ return false;
+ return integer_zerop (array_type_nelts (type));
+}
+
+/* Determine whether TYPE is a zero-length array type "[0]". */
+static bool
+zero_length_array_type_p (const_tree type)
+{
+ if (TREE_CODE (type) == ARRAY_TYPE)
+ if (tree type_size = TYPE_SIZE_UNIT (type))
+ if ((integer_zerop (type_size))
+ && TYPE_DOMAIN (type) != NULL_TREE
+ && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL_TREE)
+ return true;
+ return false;
+}
+
/* INIT is a constructor that forms DECL's initializer. If the final
element initializes a flexible array field, add the size of that
initializer to DECL's size. */
@@ -5019,10 +5054,7 @@ add_flexible_array_elts_to_size (tree decl, tree init)
elt = CONSTRUCTOR_ELTS (init)->last ().value;
type = TREE_TYPE (elt);
- if (TREE_CODE (type) == ARRAY_TYPE
- && TYPE_SIZE (type) == NULL_TREE
- && TYPE_DOMAIN (type) != NULL_TREE
- && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL_TREE)
+ if (flexible_array_member_type_p (type))
{
complete_array_type (&type, elt, false);
DECL_SIZE (decl)
@@ -8710,6 +8742,81 @@ finish_incomplete_vars (tree incomplete_vars, bool
toplevel)
}
}
+
+/* Determine whether the FIELD_DECL X is a flexible array member according to
+ the following info:
+ A. whether the FIELD_DECL X is the last field of the DECL_CONTEXT;
+ B. whether the FIELD_DECL is an array that is declared as "[]", "[0]",
+ or "[1]";
+ C. flag_strict_flex_arrays;
+ D. the attribute strict_flex_array that is attached to the field
+ if presenting.
+ Return TRUE when it's a flexible array member, FALSE otherwise. */
+
+static bool
+is_flexible_array_member_p (bool is_last_field,
+ tree x)
+{
+ /* if not the last field, return false. */
+ if (!is_last_field)
+ return false;
+
+ /* if not an array field, return false. */
+ if (TREE_CODE (TREE_TYPE (x)) != ARRAY_TYPE)
+ return false;
+
+ bool is_zero_length_array = zero_length_array_type_p (TREE_TYPE (x));
+ bool is_one_element_array = one_element_array_type_p (TREE_TYPE (x));
+ bool is_flexible_array = flexible_array_member_type_p (TREE_TYPE (x));
+
+ unsigned int strict_flex_array_level = flag_strict_flex_arrays;
+
+ tree attr_strict_flex_array = lookup_attribute ("strict_flex_arrays",
+ DECL_ATTRIBUTES (x));
+ /* if there is a strict_flex_array attribute attached to the field,
+ override the flag_strict_flex_arrays. */
+ if (attr_strict_flex_array)
+ {
+ /* get the value of the level first from the attribute. */
+ unsigned HOST_WIDE_INT attr_strict_flex_array_level = 0;
+ gcc_assert (TREE_VALUE (attr_strict_flex_array) != NULL_TREE);
+ attr_strict_flex_array = TREE_VALUE (attr_strict_flex_array);
+ gcc_assert (TREE_VALUE (attr_strict_flex_array) != NULL_TREE);
+ attr_strict_flex_array = TREE_VALUE (attr_strict_flex_array);
+ gcc_assert (tree_fits_uhwi_p (attr_strict_flex_array));
+ attr_strict_flex_array_level = tree_to_uhwi (attr_strict_flex_array);
+
+ /* the attribute has higher priority than flag_struct_flex_array. */
+ strict_flex_array_level = attr_strict_flex_array_level;
+ }
+
+ switch (strict_flex_array_level)
+ {
+ case 0:
+ /* default, all trailing arrays are flexiable array members. */
+ return true;
+ case 1:
+ /* Level 1: all "[1]", "[0]", and "[]" are flexiable array members. */
+ if (is_one_element_array)
+ return true;
+ /* FALLTHROUGH. */
+ case 2:
+ /* Level 2: all "[0]", and "[]" are flexiable array members. */
+ if (is_zero_length_array)
+ return true;
+ /* FALLTHROUGH. */
+ case 3:
+ /* Level 3: Only "[]" are flexible array members. */
+ if (is_flexible_array)
+ return true;
+ break;
+ default:
+ gcc_unreachable ();
+ }
+ return false;
+}
+
+
/* Fill in the fields of a RECORD_TYPE or UNION_TYPE node, T.
LOC is the location of the RECORD_TYPE or UNION_TYPE's definition.
FIELDLIST is a chain of FIELD_DECL nodes for the fields.
@@ -8771,6 +8878,11 @@ finish_struct (location_t loc, tree t, tree fieldlist,
tree attributes,
bool saw_named_field = false;
for (x = fieldlist; x; x = DECL_CHAIN (x))
{
+ /* whether this field is the last field of the structure or union.
+ for UNION, any field is the last field of it. */
+ bool is_last_field = (DECL_CHAIN (x) == NULL_TREE)
+ || (TREE_CODE (t) == UNION_TYPE);
+
if (TREE_TYPE (x) == error_mark_node)
continue;
@@ -8809,10 +8921,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
DECL_PACKED (x) = 1;
/* Detect flexible array member in an invalid context. */
- if (TREE_CODE (TREE_TYPE (x)) == ARRAY_TYPE
- && TYPE_SIZE (TREE_TYPE (x)) == NULL_TREE
- && TYPE_DOMAIN (TREE_TYPE (x)) != NULL_TREE
- && TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (x))) == NULL_TREE)
+ if (flexible_array_member_type_p (TREE_TYPE (x)))
{
if (TREE_CODE (t) == UNION_TYPE)
{
@@ -8820,7 +8929,7 @@ finish_struct (location_t loc, tree t, tree fieldlist,
tree attributes,
"flexible array member in union");
TREE_TYPE (x) = error_mark_node;
}
- else if (DECL_CHAIN (x) != NULL_TREE)
+ else if (!is_last_field)
{
error_at (DECL_SOURCE_LOCATION (x),
"flexible array member not at end of struct");
@@ -8840,6 +8949,9 @@ finish_struct (location_t loc, tree t, tree fieldlist,
tree attributes,
pedwarn (DECL_SOURCE_LOCATION (x), OPT_Wpedantic,
"invalid use of structure with flexible array member");
+ /* Set DECL_NOT_FLEXARRAY flag for FIELD_DECL x. */
+ DECL_NOT_FLEXARRAY (x) = !is_flexible_array_member_p (is_last_field, x);
+
if (DECL_NAME (x)
|| RECORD_OR_UNION_TYPE_P (TREE_TYPE (x)))
saw_named_field = true;
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index f27f4d091e5e..75ee2514f66b 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -5414,6 +5414,7 @@ trees_out::core_bools (tree t)
WB (t->decl_common.decl_by_reference_flag);
WB (t->decl_common.decl_read_flag);
WB (t->decl_common.decl_nonshareable_flag);
+ WB (t->decl_common.decl_not_flexarray);
}
if (CODE_CONTAINS_STRUCT (code, TS_DECL_WITH_VIS))
@@ -5558,6 +5559,7 @@ trees_in::core_bools (tree t)
RB (t->decl_common.decl_by_reference_flag);
RB (t->decl_common.decl_read_flag);
RB (t->decl_common.decl_nonshareable_flag);
+ RB (t->decl_common.decl_not_flexarray);
}
if (CODE_CONTAINS_STRUCT (code, TS_DECL_WITH_VIS))
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 0fedab96610b..62328d77c78c 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -7459,6 +7459,31 @@ This warning can be disabled by
@option{-Wno-if-not-aligned}.
The @code{warn_if_not_aligned} attribute can also be used for types
(@pxref{Common Type Attributes}.)
+@cindex @code{strict_flex_arrays} variable attribute
+@item strict_flex_arrays (@var{level})
+The @code{strict_flex_arrays} attribute should be attached to the trailing
+array field of a structure. It specifies the level of strictness of
+treating the trailing array field of a structure as a flexible array
+member. @var{level} must be an integer betwen 0 to 3.
+
+@var{level}=0 is the least strict level, all trailing arrays of structures
+are treated as flexible array members. @var{level}=3 is the strictest level,
+only when the trailing array is declared as a flexible array member per C99
+standard onwards (@samp{[]}), it is treated as a flexible array member.
+
+There are two more levels in between 0 and 3, which are provided to support
+older codes that use GCC zero-length array extension (@samp{[0]}) or one-size
+array as flexible array member (@samp{[1]}):
+When @var{level} is 1, the trailing array is treated as a flexible array member
+when it is declared as either @samp{[]}, @samp{[0]}, or @samp{[1]};
+When @var{level} is 2, the trailing array is treated as a flexible array member
+when it is declared as either @samp{[]}, or @samp{[0]}.
+
+This attribute can be used with or without the @option{-fstrict-flex-arrays}.
+When both the attribute and the option present at the same time, the level of
+the strictness for the specific trailing array field is determined by the
+attribute.
+
@item alloc_size (@var{position})
@itemx alloc_size (@var{position-1}, @var{position-2})
@cindex @code{alloc_size} variable attribute
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 9d662e353163..db1a68cd545c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -207,7 +207,8 @@ in the following sections.
-fopenmp -fopenmp-simd @gol
-fpermitted-flt-eval-methods=@var{standard} @gol
-fplan9-extensions -fsigned-bitfields -funsigned-bitfields @gol
--fsigned-char -funsigned-char -fsso-struct=@var{endianness}}
+-fsigned-char -funsigned-char -fstrict-flex-arrays[=@var{n}] @gol
+-fsso-struct=@var{endianness}}
@item C++ Language Options
@xref{C++ Dialect Options,,Options Controlling C++ Dialect}.
@@ -2826,6 +2827,30 @@ The type @code{char} is always a distinct type from each
of
@code{signed char} or @code{unsigned char}, even though its behavior
is always just like one of those two.
+@item -fstrict-flex-arrays
+@opindex fstrict-flex-arrays
+@opindex fno-strict-flex-arrays
+Treat the trailing array of a structure as a flexible array member in a
+stricter way.
+The positive form is equivalent to @option{-fstrict-flex-arrays=3}, which is
the
+strictest. A trailing array is treated as a flexible array member only when it
+is declared as a flexible array member per C99 standard onwards.
+The negative form is equivalent to @option{-fstrict-flex-arrays=0}, which is
the
+least strict. All trailing arrays of structures are treated as flexible array
+members.
+
+@item -fstrict-flex-arrays=@var{level}
+@opindex fstrict-flex-arrays=@var{level}
+Treat the trailing array of a structure as a flexible array member in a
+stricter way. The value of @var{level} controls the level of strictness.
+
+The possible values of @var{level} are the same as for the
+@code{strict_flex_arrays} attribute (@pxref{Variable Attributes}).
+
+You can control this behavior for a specific trailing array field of a
+structure by using the variable attribute @code{strict_flex_arrays} attribute
+(@pxref{Variable Attributes}).
+
@item -fsso-struct=@var{endianness}
@opindex fsso-struct
Set the default scalar storage order of structures and unions to the
diff --git a/gcc/print-tree.cc b/gcc/print-tree.cc
index 6d45a4a59669..58a98250cc4f 100644
--- a/gcc/print-tree.cc
+++ b/gcc/print-tree.cc
@@ -517,8 +517,12 @@ print_node (FILE *file, const char *prefix, tree node, int
indent,
fprintf (file, " align:%d warn_if_not_align:%d",
DECL_ALIGN (node), DECL_WARN_IF_NOT_ALIGN (node));
if (code == FIELD_DECL)
- fprintf (file, " offset_align " HOST_WIDE_INT_PRINT_UNSIGNED,
- DECL_OFFSET_ALIGN (node));
+ {
+ fprintf (file, " offset_align " HOST_WIDE_INT_PRINT_UNSIGNED,
+ DECL_OFFSET_ALIGN (node));
+ fprintf (file, " decl_not_flexarray: %d",
+ DECL_NOT_FLEXARRAY (node));
+ }
if (code == FUNCTION_DECL && fndecl_built_in_p (node))
{
diff --git a/gcc/testsuite/g++.dg/strict-flex-array-1.C
b/gcc/testsuite/g++.dg/strict-flex-array-1.C
new file mode 100644
index 000000000000..cd6a65d2b7e6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/strict-flex-array-1.C
@@ -0,0 +1,31 @@
+/* testing the correct usage of attribute strict_flex_array. */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+
+int x __attribute__ ((strict_flex_arrays (1))); /* { dg-error "'strict_flex_arrays'
attribute may not be specified for 'x'" } */
+
+struct trailing {
+ int a;
+ int c __attribute ((strict_flex_arrays)); /* { dg-error "wrong number of
arguments specified for 'strict_flex_arrays' attribute" } */
+};
+
+struct trailing_1 {
+ int a;
+ int b;
+ int c __attribute ((strict_flex_arrays (2))); /* { dg-error
"'strict_flex_arrays' attribute may not be specified for a non-array field" } */
+};
+
+extern int d;
+
+struct trailing_array_2 {
+ int a;
+ int b;
+ int c[1] __attribute ((strict_flex_arrays (d))); /* { dg-error
"'strict_flex_arrays' attribute argument not an integer" } */
+};
+
+struct trailing_array_3 {
+ int a;
+ int b;
+ int c[0] __attribute ((strict_flex_arrays (5))); /* { dg-error
"'strict_flex_arrays' attribute argument '5' is not an integer constant between 0
and 3" } */
+};
diff --git a/gcc/testsuite/gcc.dg/strict-flex-array-1.c
b/gcc/testsuite/gcc.dg/strict-flex-array-1.c
new file mode 100644
index 000000000000..cd6a65d2b7e6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/strict-flex-array-1.c
@@ -0,0 +1,31 @@
+/* testing the correct usage of attribute strict_flex_array. */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+
+int x __attribute__ ((strict_flex_arrays (1))); /* { dg-error "'strict_flex_arrays'
attribute may not be specified for 'x'" } */
+
+struct trailing {
+ int a;
+ int c __attribute ((strict_flex_arrays)); /* { dg-error "wrong number of
arguments specified for 'strict_flex_arrays' attribute" } */
+};
+
+struct trailing_1 {
+ int a;
+ int b;
+ int c __attribute ((strict_flex_arrays (2))); /* { dg-error
"'strict_flex_arrays' attribute may not be specified for a non-array field" } */
+};
+
+extern int d;
+
+struct trailing_array_2 {
+ int a;
+ int b;
+ int c[1] __attribute ((strict_flex_arrays (d))); /* { dg-error
"'strict_flex_arrays' attribute argument not an integer" } */
+};
+
+struct trailing_array_3 {
+ int a;
+ int b;
+ int c[0] __attribute ((strict_flex_arrays (5))); /* { dg-error
"'strict_flex_arrays' attribute argument '5' is not an integer constant between 0
and 3" } */
+};
diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index 80c2bcb333dd..18bd6d82a32d 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -1823,7 +1823,10 @@ struct GTY(()) tree_decl_common {
TYPE_WARN_IF_NOT_ALIGN. */
unsigned int warn_if_not_align : 6;
- /* 14 bits unused. */
+ /* In FIELD_DECL, this is DECL_NOT_FLEXARRAY. */
+ unsigned int decl_not_flexarray : 1;
+
+ /* 13 bits unused. */
/* UID for points-to sets, stable over copying from inlining. */
unsigned int pt_uid;
diff --git a/gcc/tree-streamer-in.cc b/gcc/tree-streamer-in.cc
index 219cf5e7ef45..57923da3741e 100644
--- a/gcc/tree-streamer-in.cc
+++ b/gcc/tree-streamer-in.cc
@@ -261,6 +261,7 @@ unpack_ts_decl_common_value_fields (struct bitpack_d *bp,
tree expr)
else
SET_DECL_FIELD_ABI_IGNORED (expr, val);
expr->decl_common.off_align = bp_unpack_value (bp, 8);
+ DECL_NOT_FLEXARRAY (expr) = (unsigned) bp_unpack_value (bp, 1);
}
else if (VAR_P (expr))
diff --git a/gcc/tree-streamer-out.cc b/gcc/tree-streamer-out.cc
index 9b114dc05bb1..68a2818a9f93 100644
--- a/gcc/tree-streamer-out.cc
+++ b/gcc/tree-streamer-out.cc
@@ -229,6 +229,7 @@ pack_ts_decl_common_value_fields (struct bitpack_d *bp,
tree expr)
else
bp_pack_value (bp, DECL_FIELD_ABI_IGNORED (expr), 1);
bp_pack_value (bp, expr->decl_common.off_align, 8);
+ bp_pack_value (bp, DECL_NOT_FLEXARRAY (expr), 1);
}
else if (VAR_P (expr))
diff --git a/gcc/tree.cc b/gcc/tree.cc
index 2f488e4467c4..e4664eab54ef 100644
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -12688,14 +12688,30 @@ array_ref_up_bound (tree exp)
}
/* Returns true if REF is an array reference, component reference,
- or memory reference to an array at the end of a structure.
- If this is the case, the array may be allocated larger
- than its upper bound implies. */
+ or memory reference to an array whose actual size might be larger
+ than its upper bound implies, there are multiple cases:
+ A. a ref to a flexible array member at the end of a structure;
+ B. a ref to an array with a different type against the original decl;
+ for example:
+ short a[16] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
+ (*((char(*)[16])&a[0]))[i+8]
+
+ C. a ref to an array that was passed as a parameter;
+ for example:
+
+ int test (uint8_t *p, uint32_t t[1][1], int n) {
+ for (int i = 0; i < 4; i++, p++)
+ t[i][0] = ...;
+
+ FIXME, the name of this routine need to be changed to be more accurate. */
bool
array_at_struct_end_p (tree ref)
{
- tree atype;
+ /* the TYPE for this array referece. */
+ tree atype = NULL_TREE;
+ /* the FIELD_DECL for the array field in the containing structure. */
+ tree afield_decl = NULL_TREE;
if (TREE_CODE (ref) == ARRAY_REF
|| TREE_CODE (ref) == ARRAY_RANGE_REF)
@@ -12705,7 +12721,10 @@ array_at_struct_end_p (tree ref)
}
else if (TREE_CODE (ref) == COMPONENT_REF
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 1))) == ARRAY_TYPE)
- atype = TREE_TYPE (TREE_OPERAND (ref, 1));
+ {
+ atype = TREE_TYPE (TREE_OPERAND (ref, 1));
+ afield_decl = TREE_OPERAND (ref, 1);
+ }
else if (TREE_CODE (ref) == MEM_REF)
{
tree arg = TREE_OPERAND (ref, 0);
@@ -12717,6 +12736,7 @@ array_at_struct_end_p (tree ref)
if (tree fld = last_field (argtype))
{
atype = TREE_TYPE (fld);
+ afield_decl = fld;
if (TREE_CODE (atype) != ARRAY_TYPE)
return false;
if (VAR_P (arg) && DECL_SIZE (fld))
@@ -12770,13 +12790,16 @@ array_at_struct_end_p (tree ref)
ref = TREE_OPERAND (ref, 0);
}
- /* The array now is at struct end. Treat flexible arrays as
+ gcc_assert (!afield_decl
+ || (afield_decl && TREE_CODE (afield_decl) == FIELD_DECL));
+
+ /* The array now is at struct end. Treat flexible array member as
always subject to extend, even into just padding constrained by
an underlying decl. */
if (! TYPE_SIZE (atype)
|| ! TYPE_DOMAIN (atype)
|| ! TYPE_MAX_VALUE (TYPE_DOMAIN (atype)))
- return true;
+ return afield_decl ? !DECL_NOT_FLEXARRAY (afield_decl) : true;
/* If the reference is based on a declared entity, the size of the array
is constrained by its given domain. (Do not trust commons PR/69368). */
@@ -12798,9 +12821,9 @@ array_at_struct_end_p (tree ref)
if (TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (atype))) != INTEGER_CST
|| TREE_CODE (TYPE_MAX_VALUE (TYPE_DOMAIN (atype))) != INTEGER_CST
|| TREE_CODE (TYPE_MIN_VALUE (TYPE_DOMAIN (atype))) != INTEGER_CST)
- return true;
+ return afield_decl ? !DECL_NOT_FLEXARRAY (afield_decl) : true;
if (! get_addr_base_and_unit_offset (ref_to_array, &offset))
- return true;
+ return afield_decl ? !DECL_NOT_FLEXARRAY (afield_decl) : true;
/* If at least one extra element fits it is a flexarray. */
if (known_le ((wi::to_offset (TYPE_MAX_VALUE (TYPE_DOMAIN (atype)))
@@ -12808,12 +12831,12 @@ array_at_struct_end_p (tree ref)
+ 2)
* wi::to_offset (TYPE_SIZE_UNIT (TREE_TYPE (atype))),
wi::to_offset (DECL_SIZE_UNIT (ref)) - offset))
- return true;
+ return afield_decl ? !DECL_NOT_FLEXARRAY (afield_decl) : true;
return false;
}
- return true;
+ return afield_decl ? !DECL_NOT_FLEXARRAY (afield_decl) : true;
}
/* Return a tree representing the offset, in bytes, of the field referenced
diff --git a/gcc/tree.h b/gcc/tree.h
index 266e24a05633..81076b045003 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -3005,6 +3005,12 @@ extern void decl_value_expr_insert (tree, tree);
#define DECL_PADDING_P(NODE) \
(FIELD_DECL_CHECK (NODE)->decl_common.decl_flag_3)
+/* Used in a FIELD_DECL to indicate whether this field is not a flexible
+ array member. This is only valid for the last array type field of a
+ structure. */
+#define DECL_NOT_FLEXARRAY(NODE) \
+ (FIELD_DECL_CHECK (NODE)->decl_common.decl_not_flexarray)
+
/* A numeric unique identifier for a LABEL_DECL. The UID allocation is
dense, unique within any one function, and may be used to index arrays.
If the value is -1, then no UID has been assigned. */
@@ -5543,10 +5549,10 @@ extern tree component_ref_field_offset (tree);
returns null. */
enum struct special_array_member
{
- none, /* Not a special array member. */
- int_0, /* Interior array member with size zero. */
- trail_0, /* Trailing array member with size zero. */
- trail_1 /* Trailing array member with one element. */
+ none, /* Not a special array member. */
+ int_0, /* Interior array member with size zero. */
+ trail_0, /* Trailing array member with size zero. */
+ trail_1 /* Trailing array member with one element. */
};
/* Return the size of the member referenced by the COMPONENT_REF, using
