+2012-04-12 Paul Eggert <eggert@cs.ucla.edu>
+
+ README: document pointer comparison assumption
+ * README (Portability guidelines): Document assumption about
+ pointer comparisons, in response to a recent bug-gnulib comment by
+ Jeffrey Kegler.
+
2012-04-12 Bruno Haible <bruno@clisp.org>
Tests for module 'getrusage'.
* There are no "holes" in integer values: all the bits of an integer
contribute to its value in the usual way.
- * If two nonoverlapping objects have sizes S and T represented as
- size_t values, then S + T cannot overflow. This assumption is true
- for all practical hosts with flat address spaces, but it is not
- always true for hosts with segmented address spaces.
-
- * If an existing object has size S, and if T is sufficiently small
- (e.g., 8 KiB), then S + T cannot overflow. Overflow in this case
- would mean that the rest of your program fits into T bytes, which
- can't happen in realistic flat-address-space hosts.
+ * Addresses and sizes behave as if objects reside in a flat address space.
+ In particular:
+
+ - If two nonoverlapping objects have sizes S and T represented as
+ size_t values, then S + T cannot overflow.
+
+ - A pointer P points within an object O if and only if
+ (char *) &O <= (char *) P && (char *) P < (char *) (&O + 1).
+
+ - If an existing object has size S, and if T is sufficiently small
+ (e.g., 8 KiB), then S + T cannot overflow. Overflow in this case
+ would mean that the rest of your program fits into T bytes, which
+ can't happen in realistic flat-address-space hosts.
* Objects with all bits zero are treated as 0 or NULL. For example,
memset (A, 0, sizeof A) initializes an array A of pointers to NULL.