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c-decl.c (flexible_array_type_p): New function. 

* c-decl.c (flexible_array_type_p): New function.
	(grokdeclarator, finish_struct): Use it.
	* doc/extend.texi: Document constraints on use of structures with
	flexible array members.

testsuite:
	* gcc.dg/c90-flex-array-1.c, gcc.dg/c99-flex-array-3.c,
	gcc.dg/c99-flex-array-4.c: New tests.

From-SVN: r56411
This commit is contained in:
Joseph Myers 2002-08-17 15:48:28 +01:00 committed by Joseph Myers
parent fded6d781c
commit 2984fe6496
7 changed files with 140 additions and 0 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2002-08-17 Joseph S. Myers <jsm@polyomino.org.uk>
* c-decl.c (flexible_array_type_p): New function.
(grokdeclarator, finish_struct): Use it.
* doc/extend.texi: Document constraints on use of structures with
flexible array members.
2002-08-17 Richard Sandiford <rsandifo@redhat.com>
* config/mips/t-coff, config/mips/t-elf, config/mips/t-isa3264,

43
gcc/c-decl.c
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@ -282,6 +282,7 @@ static void layout_array_type PARAMS ((tree));
static tree c_make_fname_decl PARAMS ((tree, int));
static void c_expand_body PARAMS ((tree, int, int));
static void warn_if_shadowing PARAMS ((tree, tree));
static bool flexible_array_type_p PARAMS ((tree));
/* States indicating how grokdeclarator() should handle declspecs marked
with __attribute__((deprecated)). An object declared as
@ -3357,6 +3358,40 @@ complete_array_type (type, initial_value, do_default)
return value;
}
/* Determine whether TYPE is a structure with a flexible array member,
or a union containing such a structure (possibly recursively). */
static bool
flexible_array_type_p (type)
tree type;
{
tree x;
switch (TREE_CODE (type))
{
case RECORD_TYPE:
x = TYPE_FIELDS (type);
if (x == NULL_TREE)
return false;
while (TREE_CHAIN (x) != NULL_TREE)
x = TREE_CHAIN (x);
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)
return true;
return false;
case UNION_TYPE:
for (x = TYPE_FIELDS (type); x != NULL_TREE; x = TREE_CHAIN (x))
{
if (flexible_array_type_p (TREE_TYPE (x)))
return true;
}
return false;
default:
return false;
}
}
/* Given declspecs and a declarator,
determine the name and type of the object declared
and construct a ..._DECL node for it.
@ -3953,6 +3988,9 @@ grokdeclarator (declarator, declspecs, decl_context, initialized)
type = error_mark_node;
}
if (pedantic && flexible_array_type_p (type))
pedwarn ("invalid use of structure with flexible array member");
if (size == error_mark_node)
type = error_mark_node;
@ -5216,6 +5254,11 @@ finish_struct (t, fieldlist, attributes)
else if (! saw_named_field)
error_with_decl (x, "flexible array member in otherwise empty struct");
}
if (pedantic && TREE_CODE (t) == RECORD_TYPE
&& flexible_array_type_p (TREE_TYPE (x)))
pedwarn_with_decl (x, "invalid use of structure with flexible array member");
if (DECL_NAME (x))
saw_named_field = 1;
}

6
gcc/doc/extend.texi
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@ -1293,6 +1293,12 @@ of zero-length arrays, @code{sizeof} evaluates to zero.
@item
Flexible array members may only appear as the last member of a
@code{struct} that is otherwise non-empty.
@item
A structure containing a flexible array member, or a union containing
such a structure (possibly recursively), may not be a member of a
structure or an element of an array. (However, these uses are
permitted by GCC as extensions.)
@end itemize
GCC versions before 3.0 allowed zero-length arrays to be statically

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2002-08-17 Joseph S. Myers <jsm@polyomino.org.uk>
* gcc.dg/c90-flex-array-1.c, gcc.dg/c99-flex-array-3.c,
gcc.dg/c99-flex-array-4.c: New tests.
2002-08-16 Stan Shebs <shebs@apple.com>
* objc/execute/selector-1.m: Add __NEXT_RUNTIME__ case.

7
gcc/testsuite/gcc.dg/c90-flex-array-1.c Normal file
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@ -0,0 +1,7 @@
/* Test for flexible array members. Test for rejection in C90 mode. */
/* Origin: Joseph Myers <jsm28@cam.ac.uk> */
/* { dg-do compile } */
/* { dg-options "-std=iso9899:1990 -pedantic-errors" } */
struct flex { int a; int b[]; }; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "ISO C90" "flexible array members not in C90" { target *-*-* } 6 } */

47
gcc/testsuite/gcc.dg/c99-flex-array-3.c Normal file
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@ -0,0 +1,47 @@
/* Test for flexible array members. Test for where structures with
such members may not occur. */
/* Origin: Joseph Myers <jsm28@cam.ac.uk> */
/* { dg-do compile } */
/* { dg-options "-std=iso9899:1999 -pedantic-errors" } */
struct flex { int a; int b[]; };
union rf1 { struct flex a; int b; };
union rf2 { int a; struct flex b; };
union rf3 { int a; union rf1 b; };
union rf4 { union rf2 a; int b; };
/* The above structure and unions may not be members of structures or
elements of arrays (6.7.2.1#2). */
struct t0 { struct flex a; }; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "struct in struct" { target *-*-* } 16 } */
struct t1 { union rf1 a; }; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "union in struct" { target *-*-* } 18 } */
struct t2 { union rf2 a; }; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "union in struct" { target *-*-* } 20 } */
struct t3 { union rf3 a; }; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "recursive union in struct" { target *-*-* } 22 } */
struct t4 { union rf4 a; }; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "recursive union in struct" { target *-*-* } 24 } */
void f0 (struct flex[]); /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "struct in array" { target *-*-* } 27 } */
void f1 (union rf1[]); /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "union in array" { target *-*-* } 29 } */
void f2 (union rf2[]); /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "union in array" { target *-*-* } 31 } */
void f3 (union rf3[]); /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "recursive union in array" { target *-*-* } 33 } */
void f4 (union rf4[]); /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "recursive union in array" { target *-*-* } 35 } */
struct flex a0[1]; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "struct in array" { target *-*-* } 38 } */
union rf1 a1[1]; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "union in array" { target *-*-* } 40 } */
union rf2 a2[1]; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "union in array" { target *-*-* } 42 } */
union rf3 a3[1]; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "recursive union in array" { target *-*-* } 44 } */
union rf4 a4[1]; /* { dg-bogus "warning" "warning in place of error" } */
/* { dg-error "invalid use of structure" "recursive union in array" { target *-*-* } 46 } */

25
gcc/testsuite/gcc.dg/c99-flex-array-4.c Normal file
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@ -0,0 +1,25 @@
/* Test for flexible array members. Test for agreement of offset and
structure size. This is expected to fail, because of a possible
defect in the standard. */
/* Origin: http://gcc.gnu.org/ml/gcc/2002-05/msg02844.html
from Tony Finch <dot@dotat.at>, adapted to a testcase by Joseph Myers
<jsm28@cam.ac.uk>. See also WG14 reflector messages 9571-3. */
/* { dg-do compile } */
/* { dg-options "-std=iso9899:1999 -pedantic-errors" } */
#include <stddef.h>
struct foo {
int a;
short b;
char pad[];
};
struct bar {
int a;
short b;
char pad[1024];
};
char x[(sizeof(struct foo) == offsetof(struct foo, pad)) ? 1 : -1]; /* { dg-bogus "negative" "sizeof != offsetof" { xfail *-*-* } } */
char y[(offsetof(struct foo, pad) == offsetof(struct bar, pad)) ? 1 : -1];