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c-decl.c (grokdeclarator): Support flexible array members.

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* c-decl.c (grokdeclarator): Support flexible array members.
        Use open-ended ranges for these and zero-length arrays.
        * c-typeck.c (push_init_level): Validate the context of
        initialization of a zero-length array.
        * tree.c (int_fits_type_p): Be prepared for missing bounds.
        * varasm.c (array_size_for_constructor): New.
        (output_constructor): Use it for arrays of unspecified length.
        * extend.texi (Zero Length): Mention C99 flexible array members.
        Document initialization in a top-level struct as valid.

From-SVN: r37576
This commit is contained in:
Richard Henderson 2000-11-19 15:40:37 -08:00
parent 2650255a57
commit a25f12118f
6 changed files with 118 additions and 13 deletions
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15
gcc/ChangeLog
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@ -1,3 +1,15 @@
2000-11-19 Richard Henderson <rth@redhat.com>
* c-decl.c (grokdeclarator): Support flexible array members.
Use open-ended ranges for these and zero-length arrays.
* c-typeck.c (push_init_level): Validate the context of
initialization of a zero-length array.
* tree.c (int_fits_type_p): Be prepared for missing bounds.
* varasm.c (array_size_for_constructor): New.
(output_constructor): Use it for arrays of unspecified length.
* extend.texi (Zero Length): Mention C99 flexible array members.
Document initialization in a top-level struct as valid.
2000-11-19 Joseph S. Myers <jsm28@cam.ac.uk>
* config.gcc, invoke.texi: Fix errors in spelling of "deprecated".
@ -116,8 +128,7 @@
2000-11-17 Neil Booth <neilb@earthling.net>
* cpperror.c (print_file_and_line): Don't display line number
if 0.
* cpperror.c (print_file_and_line): Don't display line number if 0.
2000-11-17 Zack Weinberg <zack@wolery.stanford.edu>

18
gcc/c-decl.c
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@ -4498,9 +4498,8 @@ grokdeclarator (declarator, declspecs, decl_context, initialized)
{
/* A zero-length array cannot be represented with an
unsigned index type, which is what we'll get with
build_index_type. Create a signed range instead. */
itype = build_range_type (index_type, size,
build_int_2 (-1, -1));
build_index_type. Create an open-ended range instead. */
itype = build_range_type (sizetype, size, NULL_TREE);
}
else
{
@ -4530,6 +4529,19 @@ grokdeclarator (declarator, declspecs, decl_context, initialized)
itype = build_index_type (itype);
}
}
else if (decl_context == FIELD)
{
/* ??? Need to check somewhere that this is a structure
and not a union, that this field is last, and that
this structure has at least one other named member. */
if (pedantic && !flag_isoc99 && !in_system_header)
pedwarn ("ISO C89 does not support flexible array members");
/* ISO C99 Flexible array members are effectively identical
to GCC's zero-length array extension. */
itype = build_range_type (sizetype, size_zero_node, NULL_TREE);
}
#if 0
/* This had bad results for pointers to arrays, as in

10
gcc/c-typeck.c
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@ -5295,6 +5295,16 @@ push_init_level (implicit)
{
constructor_max_index
= TYPE_MAX_VALUE (TYPE_DOMAIN (constructor_type));
if (constructor_max_index == NULL_TREE)
{
/* This is a zero-length array or flexible array member. */
if (pedantic)
pedwarn_init ("ISO C does not support initialization of flexible array members");
if (constructor_depth != 2)
error_init ("initialization of zero-length array inside a nested structure");
}
constructor_index
= convert (bitsizetype,
TYPE_MIN_VALUE

21
gcc/extend.texi
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@ -886,12 +886,25 @@ struct line @{
@}
@end example
In standard C, you would have to give @code{contents} a length of 1, which
In ISO C89, you would have to give @code{contents} a length of 1, which
means either you waste space or complicate the argument to @code{malloc}.
Static initialization of the zero-length array is not allowed. A
warning will be generated for each initializer attempting to initialize
the zero-length array.
In ISO C99, you would use a @dfn{flexible array member}, which uses a
slightly different syntax: leave out the @code{0} and write
@code{contents[]}.
GCC allows static initialization of the zero-length array if
the structure is not nested inside another structure. I.e.
@example
/* Legal. */
struct line x = @{ 4, @{ 'g', 'o', 'o', 'd' @} @};
/* Illegal. */
struct bar @{
struct line a;
@} y = @{ @{ 3, @{ 'b', 'a', 'd' @} @} @};
@end example
@node Variable Length
@section Arrays of Variable Length

4
gcc/tree.c
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@ -4186,7 +4186,9 @@ int_fits_type_p (c, type)
{
/* If the bounds of the type are integers, we can check ourselves.
Otherwise,. use force_fit_type, which checks against the precision. */
if (TREE_CODE (TYPE_MAX_VALUE (type)) == INTEGER_CST
if (TYPE_MAX_VALUE (type) != NULL_TREE
&& TYPE_MIN_VALUE (type) != NULL_TREE
&& TREE_CODE (TYPE_MAX_VALUE (type)) == INTEGER_CST
&& TREE_CODE (TYPE_MIN_VALUE (type)) == INTEGER_CST)
{
if (TREE_UNSIGNED (type))

63
gcc/varasm.c
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@ -171,6 +171,7 @@ static void mark_constant_pool PARAMS ((void));
static void mark_constants PARAMS ((rtx));
static int output_addressed_constants PARAMS ((tree));
static void output_after_function_constants PARAMS ((void));
static int array_size_for_constructor PARAMS ((tree));
static void output_constructor PARAMS ((tree, int));
#ifdef ASM_WEAKEN_LABEL
static void remove_from_pending_weak_list PARAMS ((const char *));
@ -4413,8 +4414,53 @@ output_constant (exp, size)
}
/* Subroutine of output_constant, used for CONSTRUCTORs
(aggregate constants).
/* Subroutine of output_constructor, used for computing the size of
arrays of unspecified length. VAL must be a CONSTRUCTOR of an array
type with an unspecified upper bound. */
static int
array_size_for_constructor (val)
tree val;
{
tree max_index, i;
if (!val || TREE_CODE (val) != CONSTRUCTOR
|| TREE_CODE (TREE_TYPE (val)) != ARRAY_TYPE
|| TYPE_DOMAIN (TREE_TYPE (val)) == NULL_TREE
|| TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (val))) != NULL_TREE
|| TYPE_MIN_VALUE (TYPE_DOMAIN (TREE_TYPE (val))) == NULL_TREE)
abort ();
max_index = NULL_TREE;
for (i = CONSTRUCTOR_ELTS (val); i ; i = TREE_CHAIN (i))
{
tree index = TREE_PURPOSE (i);
if (TREE_CODE (index) == RANGE_EXPR)
index = TREE_OPERAND (index, 1);
if (max_index == NULL_TREE || tree_int_cst_lt (max_index, index))
max_index = index;
}
/* ??? I'm fairly certain if there were no elements, we shouldn't have
created the constructor in the first place. */
if (max_index == NULL_TREE)
abort ();
/* Compute the total number of array elements. */
i = fold (build (MINUS_EXPR, TREE_TYPE (max_index), max_index,
TYPE_MIN_VALUE (TYPE_DOMAIN (TREE_TYPE (val)))));
i = fold (build (PLUS_EXPR, TREE_TYPE (i), i,
convert (TREE_TYPE (i), integer_one_node)));
/* Multiply by the array element unit size to find number of bytes. */
i = fold (build (MULT_EXPR, TREE_TYPE (max_index), i,
TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (val)))));
return tree_low_cst (i, 1);
}
/* Subroutine of output_constant, used for CONSTRUCTORs (aggregate constants).
Generate at least SIZE bytes, padding if necessary. */
static void
@ -4532,7 +4578,18 @@ output_constructor (exp, size)
/* Determine size this element should occupy. */
if (field)
fieldsize = tree_low_cst (DECL_SIZE_UNIT (field), 1);
{
if (DECL_SIZE_UNIT (field))
fieldsize = tree_low_cst (DECL_SIZE_UNIT (field), 1);
else
{
/* If DECL_SIZE is not set, then this must be an array
of unspecified length. The initialized value must
be a CONSTRUCTOR, and we take the length from the
last initialized element. */
fieldsize = array_size_for_constructor (val);
}
}
else
fieldsize = int_size_in_bytes (TREE_TYPE (type));