re PR c/3259 (({ }) and -Wall)

	* c-common.c (verify_tree): Check for x being NULL.
	* doc/c-tree.texi: Document COMPOUND_BODY of an empty
	COMPOUND_STMT.
	Fixes PR c/3259.

testsuite:
	* gcc.dg/20010622-1.c: New test.

From-SVN: r43508

gcc/ChangeLog

+2001-06-22  Joseph S. Myers  <jsm28@cam.ac.uk>
+
+	* c-common.c (verify_tree): Check for x being NULL.
+	* doc/c-tree.texi: Document COMPOUND_BODY of an empty
+	COMPOUND_STMT.
+	Fixes PR c/3259.
+
 2001-06-22  DJ Delorie  <dj@redhat.com>
 
 	* config/arm/arm.h (struct machine_function): Remove ra_rtx.

gcc/c-common.c

@@ -1592,6 +1592,11 @@ verify_tree (x, pbefore_sp, pno_sp, writer)
   enum tree_code code;
   char class;
 
+  /* X may be NULL if it is the operand of an empty statement expression
+     ({ }).  */
+  if (x == NULL)
+    return;
+
  restart:
   code = TREE_CODE (x);
   class = TREE_CODE_CLASS (code);

gcc/doc/c-tree.texi

@@ -1473,6 +1473,8 @@ should be run in the reverse order of the order in which the associated
 Used to represent a brace-enclosed block.  The first substatement is
 given by @code{COMPOUND_BODY}.  Subsequent substatements are found by
 following the @code{TREE_CHAIN} link from one substatement to the next.
+The @code{COMPOUND_BODY} will be @code{NULL_TREE} if there are no
+substatements.
 
 @item CONTINUE_STMT
 

gcc/testsuite/ChangeLog

+2001-06-22  Joseph S. Myers  <jsm28@cam.ac.uk>
+
+	* gcc.dg/20010622-1.c: New test.
+
 2001-06-18  Stan Shebs  <shebs@apple.com>
 
 	* objc.dg: New directory.

gcc/testsuite/gcc.dg/20010622-1.c

+/* Test for segfault doing -Wsequence-point processing on an empty
+   statement expression.  */
+/* Origin: PR c/3259 from <David.Decotigny@irisa.fr>.  */
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+void
+f (void)
+{
+  ({ });
+}