[Help] Add bounds checking to TREE_VEC_ELT

[Zack Weinberg <zack at codesourcery dot com>]

I noticed that we make no attempt to bounds-check TREE_VEC_ELT
accesses.  The appended patch adds this checking.  Unfortunately, it
breaks the compiler quite thoroughly:

crtstuff.c: In function `__do_global_dtors_aux':
crtstuff.c:280: internal compiler error: tree check:
  accessed elt 0 of tree_vec with 0 elts in optimize_inline_calls, 
  at tree-inline.c:1370

[note that TREE_VEC_ELT is 0-based - a TREE_VEC with 0 elts can't be
used at all]

I'm sure there are more bugs than just this one.  I need to go to bed
now; anyone interested in squishing all said bugs before I get up
tomorrow morning?  -_^

zw

	* tree.h (TREE_VEC_ELT_CHECK): New checking macro - applies
	array bounds check for TREE_VECs.
	(TREE_VEC_ELT): Use it.
	* tree.c (tree_vec_elt_check_failed): New function.

===================================================================
Index: tree.c
--- tree.c	23 Oct 2002 17:13:15 -0000	1.278
+++ tree.c	13 Nov 2002 09:22:13 -0000
@@ -4665,6 +4665,22 @@ tree_class_check_failed (node, cl, file,
      tree_code_name[TREE_CODE (node)], function, trim_filename (file), line);
 }
 
+/* Similar to above, except that the check is for the bounds of a TREE_VEC's
+   (dynamically sized) vector.  */
+
+void
+tree_vec_elt_check_failed (idx, len, file, line, function)
+     int idx;
+     int len;
+     const char *file;
+     int line;
+     const char *function;
+{
+  internal_error
+    ("tree check: accessed elt %d of tree_vec with %d elts in %s, at %s:%d",
+     idx, len, function, trim_filename (file), line);
+}
+
 #endif /* ENABLE_TREE_CHECKING */
 
 /* For a new vector type node T, build the information necessary for
===================================================================
Index: tree.h
--- tree.h	23 Oct 2002 17:13:15 -0000	1.360
+++ tree.h	13 Nov 2002 09:22:14 -0000
@@ -317,12 +317,26 @@ struct tree_common GTY(())
 			       __FUNCTION__);				\
     __t; })
 
+#define TREE_VEC_ELT_CHECK(t, i) __extension__				\
+(*({const tree __t = t;							\
+    const int __i = (i);						\
+    if (TREE_CODE (__t) != TREE_VEC)					\
+      tree_check_failed (__t, TREE_VEC,					\
+			 __FILE__, __LINE__, __FUNCTION__);		\
+    if (i < 0 || i >= __t->vec.length)					\
+      tree_vec_elt_check_failed (i, __t->vec.length,			\
+				 __FILE__, __LINE__, __FUNCTION__);	\
+    &__t->vec.a[__i]; }))
+
 extern void tree_check_failed PARAMS ((const tree, enum tree_code,
 				       const char *, int, const char *))
     ATTRIBUTE_NORETURN;
 extern void tree_class_check_failed PARAMS ((const tree, int,
 					     const char *, int, const char *))
     ATTRIBUTE_NORETURN;
+extern void tree_vec_elt_check_failed PARAMS ((int, int, const char *,
+					       int, const char *))
+    ATTRIBUTE_NORETURN;
 
 #else /* not ENABLE_TREE_CHECKING, or not gcc */
 
@@ -330,6 +344,7 @@ extern void tree_class_check_failed PARA
 #define TREE_CLASS_CHECK(t, code)	(t)
 #define CST_OR_CONSTRUCTOR_CHECK(t)	(t)
 #define EXPR_CHECK(t)			(t)
+#define TREE_VEC_ELT_CHECK(t, i)	((t)->vec.a[i])
 
 #endif
 
@@ -810,9 +825,10 @@ struct tree_list GTY(())
 
 /* In a TREE_VEC node.  */
 #define TREE_VEC_LENGTH(NODE) (TREE_VEC_CHECK (NODE)->vec.length)
-#define TREE_VEC_ELT(NODE,I) (TREE_VEC_CHECK (NODE)->vec.a[I])
 #define TREE_VEC_END(NODE) \
   ((void) TREE_VEC_CHECK (NODE), &((NODE)->vec.a[(NODE)->vec.length]))
+
+#define TREE_VEC_ELT(NODE,I) TREE_VEC_ELT_CHECK (NODE, I)
 
 struct tree_vec GTY(())
 {