This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Bit-field patch, part 1
- From: "Joseph S. Myers" <jsm at polyomino dot org dot uk>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 17 Dec 2003 00:26:14 +0000 (UTC)
- Subject: Bit-field patch, part 1
The following patch is the easy part of resurrecting the bit-field
patch: moving the validation of bit-field types and widths to a
separate function. This fixes one of the underlying bug reports (PR
c/3347, bit-fields that are too wide should be hard errors), and as it
doesn't include the part giving bit-fields their correct types it
should be less problematic than the rest of the patch. It should also
be sufficient for RTH's patch (always warning for enum bit-fields with
-pedantic) not to require additional complexity to save the pedantic
setting.
(Neil's original patch combined checking type and width with
generating the correct type for the bit-field. I've found it
necessary to separate these - preserving the separate width and
original type until finish_struct - to get the correct layout in
various cases.)
Bootstrapped with no regressions on i686-pc-linux-gnu. Applied to
mainline.
2003-12-17 Neil Booth <neil@daikokuya.co.uk>
Joseph S. Myers <jsm@polyomino.org.uk>
PR c/3347
* c-decl.c (enum_decl_context): Remove BITFIELD.
(grokdeclarator): Take bit-field width as an input.
Perform bit-field width validation with
check_bitfield_type_and_width rather than waiting for
finish_struct.
(groktypename, groktypename_in_parm_context, start_decl,
push_parm_decl, grokfield, start_function): Update calls to
grokdeclarator.
(check_bitfield_type_and_width): New function.
(finish_struct): Move bit-field validation to grokdeclarator
and check_bitfield_type_and_width.
2003-12-17 Joseph S. Myers <jsm@polyomino.org.uk>
PR c/3347
* gcc.dg/bitfld-8.c: New test.
diff -rupN GCC.orig/gcc/c-decl.c GCC-part1/gcc/c-decl.c
--- GCC.orig/gcc/c-decl.c 2003-11-26 13:49:04.000000000 +0000
+++ GCC-part1/gcc/c-decl.c 2003-12-16 10:17:33.000000000 +0000
@@ -61,7 +61,6 @@ enum decl_context
FUNCDEF, /* Function definition */
PARM, /* Declaration of parm before function body */
FIELD, /* Declaration inside struct or union */
- BITFIELD, /* Likewise but with specified width */
TYPENAME}; /* Typename (inside cast or sizeof) */
@@ -315,7 +314,7 @@ static void bind_label (tree, tree, stru
static void implicit_decl_warning (tree);
static tree lookup_tag (enum tree_code, tree, int);
static tree lookup_name_current_level (tree);
-static tree grokdeclarator (tree, tree, enum decl_context, int);
+static tree grokdeclarator (tree, tree, enum decl_context, int, tree *);
static tree grokparms (tree, int);
static void layout_array_type (tree);
static void store_parm_decls_newstyle (void);
@@ -325,6 +324,7 @@ static void c_expand_body_1 (tree, int);
static tree any_external_decl (tree);
static void record_external_decl (tree);
static void warn_if_shadowing (tree, tree);
+static void check_bitfield_type_and_width (tree *, tree *, const char *);
static void clone_underlying_type (tree);
static bool flexible_array_type_p (tree);
static hashval_t link_hash_hash (const void *);
@@ -2527,7 +2527,8 @@ groktypename (tree typename)
split_specs_attrs (TREE_PURPOSE (typename), &specs, &attrs);
- typename = grokdeclarator (TREE_VALUE (typename), specs, TYPENAME, 0);
+ typename = grokdeclarator (TREE_VALUE (typename), specs, TYPENAME, 0,
+ NULL);
/* Apply attributes. */
decl_attributes (&typename, attrs, 0);
@@ -2544,7 +2545,7 @@ groktypename_in_parm_context (tree typen
return typename;
return grokdeclarator (TREE_VALUE (typename),
TREE_PURPOSE (typename),
- PARM, 0);
+ PARM, 0, NULL);
}
/* Decode a declarator in an ordinary declaration or data definition.
@@ -2574,7 +2575,7 @@ start_decl (tree declarator, tree declsp
deprecated_state = DEPRECATED_SUPPRESS;
decl = grokdeclarator (declarator, declspecs,
- NORMAL, initialized);
+ NORMAL, initialized, NULL);
deprecated_state = DEPRECATED_NORMAL;
@@ -3010,7 +3011,8 @@ push_parm_decl (tree parm)
immediate_size_expand = 0;
decl = grokdeclarator (TREE_VALUE (TREE_PURPOSE (parm)),
- TREE_PURPOSE (TREE_PURPOSE (parm)), PARM, 0);
+ TREE_PURPOSE (TREE_PURPOSE (parm)),
+ PARM, 0, NULL);
decl_attributes (&decl, TREE_VALUE (parm), 0);
decl = pushdecl (decl);
@@ -3205,6 +3207,80 @@ flexible_array_type_p (tree type)
}
}
+/* Performs sanity checks on the TYPE and WIDTH of the bit-field NAME,
+ replacing with appropriate values if they are invalid. */
+static void
+check_bitfield_type_and_width (tree *type, tree *width, const char *orig_name)
+{
+ tree type_mv;
+ unsigned int max_width;
+ unsigned HOST_WIDE_INT w;
+ const char *name = orig_name ? orig_name: _("<anonymous>");
+
+ /* Necessary? */
+ STRIP_NOPS (*width);
+
+ /* Detect and ignore out of range field width and process valid
+ field widths. */
+ if (TREE_CODE (*width) != INTEGER_CST)
+ {
+ error ("bit-field `%s' width not an integer constant", name);
+ *width = integer_one_node;
+ }
+ else
+ {
+ constant_expression_warning (*width);
+ if (tree_int_cst_sgn (*width) < 0)
+ {
+ error ("negative width in bit-field `%s'", name);
+ *width = integer_one_node;
+ }
+ else if (integer_zerop (*width) && orig_name)
+ {
+ error ("zero width for bit-field `%s'", name);
+ *width = integer_one_node;
+ }
+ }
+
+ /* Detect invalid bit-field type. */
+ if (TREE_CODE (*type) != INTEGER_TYPE
+ && TREE_CODE (*type) != BOOLEAN_TYPE
+ && TREE_CODE (*type) != ENUMERAL_TYPE)
+ {
+ error ("bit-field `%s' has invalid type", name);
+ *type = unsigned_type_node;
+ }
+
+ type_mv = TYPE_MAIN_VARIANT (*type);
+ if (pedantic
+ && type_mv != integer_type_node
+ && type_mv != unsigned_type_node
+ && type_mv != boolean_type_node
+ /* Accept an enum that's equivalent to int or unsigned int. */
+ && (TREE_CODE (*type) != ENUMERAL_TYPE
+ || TYPE_PRECISION (*type) != TYPE_PRECISION (integer_type_node)))
+ pedwarn ("type of bit-field `%s' is a GCC extension", name);
+
+ if (type_mv == boolean_type_node)
+ max_width = CHAR_TYPE_SIZE;
+ else
+ max_width = TYPE_PRECISION (*type);
+
+ if (0 < compare_tree_int (*width, max_width))
+ {
+ error ("width of `%s' exceeds its type", name);
+ w = max_width;
+ *width = build_int_2 (w, 0);
+ }
+ else
+ w = tree_low_cst (*width, 1);
+
+ if (TREE_CODE (*type) == ENUMERAL_TYPE
+ && (w < min_precision (TYPE_MIN_VALUE (*type), TREE_UNSIGNED (*type))
+ || w < min_precision (TYPE_MAX_VALUE (*type), TREE_UNSIGNED (*type))))
+ warning ("`%s' is narrower than values of its type", name);
+}
+
/* Given declspecs and a declarator,
determine the name and type of the object declared
and construct a ..._DECL node for it.
@@ -3224,8 +3300,9 @@ flexible_array_type_p (tree type)
TYPENAME if for a typename (in a cast or sizeof).
Don't make a DECL node; just return the ..._TYPE node.
FIELD for a struct or union field; make a FIELD_DECL.
- BITFIELD for a field with specified width.
INITIALIZED is 1 if the decl has an initializer.
+ WIDTH is non-NULL for bit-fields, and is a pointer to an INTEGER_CST node
+ representing the width of the bit-field.
In the TYPENAME case, DECLARATOR is really an absolute declarator.
It may also be so in the PARM case, for a prototype where the
@@ -3236,7 +3313,7 @@ flexible_array_type_p (tree type)
static tree
grokdeclarator (tree declarator, tree declspecs,
- enum decl_context decl_context, int initialized)
+ enum decl_context decl_context, int initialized, tree *width)
{
int specbits = 0;
tree spec;
@@ -3251,19 +3328,16 @@ grokdeclarator (tree declarator, tree de
int explicit_char = 0;
int defaulted_int = 0;
tree typedef_decl = 0;
- const char *name;
+ const char *name, *orig_name;
tree typedef_type = 0;
int funcdef_flag = 0;
enum tree_code innermost_code = ERROR_MARK;
- int bitfield = 0;
int size_varies = 0;
tree decl_attr = NULL_TREE;
tree array_ptr_quals = NULL_TREE;
int array_parm_static = 0;
tree returned_attrs = NULL_TREE;
-
- if (decl_context == BITFIELD)
- bitfield = 1, decl_context = FIELD;
+ bool bitfield = width != NULL;
if (decl_context == FUNCDEF)
funcdef_flag = 1, decl_context = NORMAL;
@@ -3296,6 +3370,7 @@ grokdeclarator (tree declarator, tree de
default:
abort ();
}
+ orig_name = name;
if (name == 0)
name = "type name";
}
@@ -3528,7 +3603,7 @@ grokdeclarator (tree declarator, tree de
}
/* Decide whether an integer type is signed or not.
- Optionally treat bitfields as signed by default. */
+ Optionally treat bit-fields as signed by default. */
if (specbits & 1 << (int) RID_UNSIGNED
|| (bitfield && ! flag_signed_bitfields
&& (explicit_int || defaulted_int || explicit_char
@@ -3600,6 +3675,10 @@ grokdeclarator (tree declarator, tree de
}
}
+ /* Check the type and width of a bit-field. */
+ if (bitfield)
+ check_bitfield_type_and_width (&type, width, orig_name);
+
/* Figure out the type qualifiers for the declaration. There are
two ways a declaration can become qualified. One is something
like `const int i' where the `const' is explicit. Another is
@@ -4756,7 +4835,7 @@ start_struct (enum tree_code code, tree
/* Process the specs, declarator (NULL if omitted) and width (NULL if omitted)
of a structure component, returning a FIELD_DECL node.
- WIDTH is non-NULL for bit fields only, and is an INTEGER_CST node.
+ WIDTH is non-NULL for bit-fields only, and is an INTEGER_CST node.
This is done during the parsing of the struct declaration.
The FIELD_DECL nodes are chained together and the lot of them
@@ -4811,7 +4890,8 @@ grokfield (tree declarator, tree declspe
}
}
- value = grokdeclarator (declarator, declspecs, width ? BITFIELD : FIELD, 0);
+ value = grokdeclarator (declarator, declspecs, FIELD, 0,
+ width ? &width : NULL);
finish_decl (value, NULL_TREE, NULL_TREE);
DECL_INITIAL (value) = width;
@@ -4958,72 +5038,12 @@ finish_struct (tree t, tree fieldlist, t
error ("nested redefinition of `%s'",
IDENTIFIER_POINTER (TYPE_NAME (t)));
- /* Detect invalid bit-field size. */
- if (DECL_INITIAL (x))
- STRIP_NOPS (DECL_INITIAL (x));
if (DECL_INITIAL (x))
{
- if (TREE_CODE (DECL_INITIAL (x)) == INTEGER_CST)
- constant_expression_warning (DECL_INITIAL (x));
- else
- {
- error ("%Jbit-field '%D' width not an integer constant", x, x);
- DECL_INITIAL (x) = NULL;
- }
- }
-
- /* Detect invalid bit-field type. */
- if (DECL_INITIAL (x)
- && TREE_CODE (TREE_TYPE (x)) != INTEGER_TYPE
- && TREE_CODE (TREE_TYPE (x)) != BOOLEAN_TYPE
- && TREE_CODE (TREE_TYPE (x)) != ENUMERAL_TYPE)
- {
- error ("%Jbit-field '%D' has invalid type", x, x);
- DECL_INITIAL (x) = NULL;
- }
-
- if (DECL_INITIAL (x) && pedantic
- && TYPE_MAIN_VARIANT (TREE_TYPE (x)) != integer_type_node
- && TYPE_MAIN_VARIANT (TREE_TYPE (x)) != unsigned_type_node
- && TYPE_MAIN_VARIANT (TREE_TYPE (x)) != boolean_type_node
- /* Accept an enum that's equivalent to int or unsigned int. */
- && !(TREE_CODE (TREE_TYPE (x)) == ENUMERAL_TYPE
- && (TYPE_PRECISION (TREE_TYPE (x))
- == TYPE_PRECISION (integer_type_node))))
- pedwarn ("%Jbit-field '%D' type invalid in ISO C", x, x);
-
- /* Detect and ignore out of range field width and process valid
- field widths. */
- if (DECL_INITIAL (x))
- {
- int max_width
- = (TYPE_MAIN_VARIANT (TREE_TYPE (x)) == boolean_type_node
- ? CHAR_TYPE_SIZE : TYPE_PRECISION (TREE_TYPE (x)));
-
- if (tree_int_cst_sgn (DECL_INITIAL (x)) < 0)
- error ("%Jnegative width in bit-field '%D'", x, x);
- else if (0 < compare_tree_int (DECL_INITIAL (x), max_width))
- pedwarn ("%Jwidth of '%D' exceeds its type", x, x);
- else if (integer_zerop (DECL_INITIAL (x)) && DECL_NAME (x) != 0)
- error ("%Jzero width for bit-field '%D'", x, x);
- else
- {
- /* The test above has assured us that TREE_INT_CST_HIGH is 0. */
- unsigned HOST_WIDE_INT width
- = tree_low_cst (DECL_INITIAL (x), 1);
-
- if (TREE_CODE (TREE_TYPE (x)) == ENUMERAL_TYPE
- && (width < min_precision (TYPE_MIN_VALUE (TREE_TYPE (x)),
- TREE_UNSIGNED (TREE_TYPE (x)))
- || (width
- < min_precision (TYPE_MAX_VALUE (TREE_TYPE (x)),
- TREE_UNSIGNED (TREE_TYPE (x))))))
- warning ("%J'%D' is narrower than values of its type", x, x);
-
- DECL_SIZE (x) = bitsize_int (width);
- DECL_BIT_FIELD (x) = 1;
- SET_DECL_C_BIT_FIELD (x);
- }
+ unsigned HOST_WIDE_INT width = tree_low_cst (DECL_INITIAL (x), 1);
+ DECL_SIZE (x) = bitsize_int (width);
+ DECL_BIT_FIELD (x) = 1;
+ SET_DECL_C_BIT_FIELD (x);
}
DECL_INITIAL (x) = 0;
@@ -5448,7 +5468,7 @@ start_function (tree declspecs, tree dec
/* Don't expand any sizes in the return type of the function. */
immediate_size_expand = 0;
- decl1 = grokdeclarator (declarator, declspecs, FUNCDEF, 1);
+ decl1 = grokdeclarator (declarator, declspecs, FUNCDEF, 1, NULL);
/* If the declarator is not suitable for a function definition,
cause a syntax error. */
diff -rupN GCC.orig/gcc/testsuite/gcc.dg/bitfld-8.c GCC-part1/gcc/testsuite/gcc.dg/bitfld-8.c
--- GCC.orig/gcc/testsuite/gcc.dg/bitfld-8.c 1970-01-01 00:00:00.000000000 +0000
+++ GCC-part1/gcc/testsuite/gcc.dg/bitfld-8.c 2003-12-16 10:21:01.000000000 +0000
@@ -0,0 +1,7 @@
+/* Test that too wide bit-fields are hard errors. PR c/3347. */
+/* Origin: Joseph Myers <jsm@polyomino.org.uk>, from PR c/3347 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+struct { int i : 1999; } x; /* { dg-bogus "warning" "warning in place of error" } */
+/* { dg-error "width" "bit-field too wide" { target *-*-* } 6 } */
--
Joseph S. Myers
jsm@polyomino.org.uk