From 1879e48f3d8595bc9e7f583bbd12df3c6f5c42dc Mon Sep 17 00:00:00 2001 From: Qing Zhao Date: Fri, 7 Oct 2022 14:58:20 +0000 Subject: Add a new option -fstrict-flex-arrays[=n] and new attribute strict_flex_array Add the following new option -fstrict-flex-arrays[=n] and a corresponding attribute strict_flex_array to GCC: '-fstrict-flex-arrays' Control when to treat the trailing array of a structure as a flexible array member for the purpose of accessing the elements of such an array. The positive form is equivalent to '-fstrict-flex-arrays=3', which is the strictest. A trailing array is treated as a flexible array member only when it declared as a flexible array member per C99 standard onwards. The negative form is equivalent to '-fstrict-flex-arrays=0', which is the least strict. All trailing arrays of structures are treated as flexible array members. '-fstrict-flex-arrays=LEVEL' Control when to treat the trailing array of a structure as a flexible array member for the purpose of accessing the elements of such an array. The value of LEVEL controls the level of strictness The possible values of LEVEL are the same as for the 'strict_flex_array' attribute (*note Variable Attributes::). You can control this behavior for a specific trailing array field of a structure by using the variable attribute 'strict_flex_array' attribute (*note Variable Attributes::). 'strict_flex_array (LEVEL)' The 'strict_flex_array' attribute should be attached to the trailing array field of a structure. It controls when to treat the trailing array field of a structure as a flexible array member for the purposes of accessing the elements of such an array. LEVEL must be an integer betwen 0 to 3. 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-element array as flexible array members('[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_array_attribute): New function. (c_common_attribute_table): New item for strict_flex_array. * 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_array 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/tree.h | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'gcc/tree.h') diff --git a/gcc/tree.h b/gcc/tree.h index 95285e4..142e9c9 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. */ @@ -5547,10 +5553,10 @@ 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 -- cgit v1.1