null considered harmful considered harmful

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/stddef.h b/include/stddef.h
index 275e53c..0e10989 100644
--- a/include/stddef.h
+++ b/include/stddef.h
@@ -28,6 +28,18 @@
  * the same width and ISO C does not specify it this
  * way), use to indicate that a pointer does not point
  * to anything.
+ * 
+ * Note on considerations of `NULL` being harmful:
+ *   It is important to remember than `sizeof(NULL)`
+ *   does not equal `sizeof(int)` on all machines.
+ *   Therefore, in variadic arguments, it is important
+ *   not to substitute `x` for `x != NULL`. This
+ *   would cause horrible bugs. If you insist on not
+ *   using `NULL`, correct substitutions would be
+ *   `!!x` or `x != 0`.
+ * Note that `NULL` is genuinely harmful in C++,
+ * but excessive use of C++, and especially it
+ * features, is harmful too.
  */
 #ifndef NULL
 # define NULL  ((void*)0)