PATCH for sanity checking of nesting code

[Jason Merrill]

I've had this in my tree for a few weeks, since I tracked down a bug
involving mismatched push/pops and EH.

Applied to trunk.

2001-06-08  Jason Merrill  <jason_merrill@redhat.com>

	* stmt.c (current_nesting_level): New fn.
	* tree.h: Declare it.
	* c-semantics.c (genrtl_compound_stmt): Use it.

*** c-semantics.c.~1~	Wed Jun  6 15:20:55 2001
--- c-semantics.c	Fri Jun  8 17:30:20 2001
*************** void
*** 666,672 ****
--- 666,682 ----
  genrtl_compound_stmt (t)
      tree t;
  {
+ #ifdef ENABLE_CHECKING
+   struct nesting *n = current_nesting_level ();
+ #endif
+ 
    expand_stmt (COMPOUND_BODY (t));
+ 
+ #ifdef ENABLE_CHECKING
+   /* Make sure that we've pushed and popped the same number of levels.  */
+   if (n != current_nesting_level ())
+     abort ();
+ #endif
  }
  
  /* Generate the RTL for an ASM_STMT. */
*** stmt.c.~1~	Wed Jun  6 15:20:55 2001
--- stmt.c	Mon May 21 17:04:43 2001
*************** conditional_context ()
*** 3395,3400 ****
--- 3395,3409 ----
    return block_stack && block_stack->data.block.conditional_code;
  }
  
+ /* Return an opaque pointer to the current nesting level, so frontend code
+    can check its own sanity.  */
+ 
+ struct nesting *
+ current_nesting_level ()
+ {
+   return cfun ? block_stack : 0;
+ }
+ 
  /* Emit a handler label for a nonlocal goto handler.
     Also emit code to store the handler label in SLOT before BEFORE_INSN.  */
  
*** tree.h.~1~	Wed Jun  6 15:20:55 2001
--- tree.h	Fri Jun  8 19:05:33 2001
*************** extern void end_cleanup_deferral		PARAMS
*** 2564,2569 ****
--- 2567,2573 ----
  extern int is_body_block			PARAMS ((tree));
  
  extern int conditional_context			PARAMS ((void));
+ extern struct nesting * current_nesting_level	PARAMS ((void));
  extern tree last_cleanup_this_contour		PARAMS ((void));
  extern void expand_start_case			PARAMS ((int, tree, tree,
  						       const char *));