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

7 files changed, 140 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4510a07..8ebb481 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -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,
diff --git a/gcc/c-decl.c b/gcc/c-decl.c
index 7a926cf..d61d955 100644
--- a/gcc/c-decl.c
+++ b/gcc/c-decl.c
@@ -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;
     }
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 4814b35..32fabae 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -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
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index bd0a52f..dad59ab 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -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.
diff --git a/gcc/testsuite/gcc.dg/c90-flex-array-1.c b/gcc/testsuite/gcc.dg/c90-flex-array-1.c
new file mode 100644
index 0000000..1eead19
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c90-flex-array-1.c
@@ -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 } */
diff --git a/gcc/testsuite/gcc.dg/c99-flex-array-3.c b/gcc/testsuite/gcc.dg/c99-flex-array-3.c
new file mode 100644
index 0000000..e8647f6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c99-flex-array-3.c
@@ -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 } */
diff --git a/gcc/testsuite/gcc.dg/c99-flex-array-4.c b/gcc/testsuite/gcc.dg/c99-flex-array-4.c
new file mode 100644
index 0000000..ab20cf0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c99-flex-array-4.c
@@ -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];