[Emacs-diffs] Changes to emacs/src/lisp.h,v

[Ken Raeburn]

CVSROOT:        /cvsroot/emacs
Module name:    emacs
Changes by:     Ken Raeburn <raeburn>   07/10/29 18:15:03

Index: lisp.h
===================================================================
RCS file: /cvsroot/emacs/emacs/src/lisp.h,v
retrieving revision 1.598
retrieving revision 1.599
diff -u -b -r1.598 -r1.599
--- lisp.h      23 Oct 2007 21:17:06 -0000      1.598
+++ lisp.h      29 Oct 2007 18:15:02 -0000      1.599
@@ -84,6 +84,20 @@
 
 #ifdef ENABLE_CHECKING
 
+/* The suppress_checking variable is initialized to 0 in alloc.c.  Set
+   it to 1 using a debugger to temporarily disable aborting on
+   detected internal inconsistencies or error conditions.
+
+   Testing suppress_checking after the supplied condition ensures that
+   the side effects produced by CHECK will be consistent, independent
+   of whether ENABLE_CHECKING is defined, or whether the checks are
+   suppressed at run time.
+
+   In some cases, a good compiler may be able to optimize away the
+   CHECK macro altogether, e.g., if XSTRING (x) uses CHECK to test
+   STRINGP (x), but a particular use of XSTRING is invoked only after
+   testing that STRINGP (x) is true, making the test redundant.  */
+
 #define CHECK(check,msg) (((check) || suppress_checking                \
                           ? (void) 0                           \
                           : die ((msg), __FILE__, __LINE__)),  \