+2021-08-30 Paul Eggert <eggert@cs.ucla.edu>
+
+ idx: add commentary
+ * lib/idx.h: Add comments about ssize_t and strlen, in
+ response to comments from Simon Josefsson in:
+ https://lists.gnu.org/r/bug-gnulib/2021-08/msg00196.html
+
2021-08-29 Paul Eggert <eggert@cs.ucla.edu>
attribute: keep up with gnulib-common.m4
* Because 'size_t' is an unsigned type, and a signed type is better.
See above.
+ Why not use 'ssize_t'?
+
+ * 'ptrdiff_t' is more portable; it is standardized by ISO C
+ whereas 'ssize_t' is standardized only by POSIX.
+
+ * 'ssize_t' is not required to be as wide as 'size_t', and some
+ now-obsolete POSIX platforms had 'size_t' wider than 'ssize_t'.
+
+ * Conversely, some now-obsolete platforms had 'ptrdiff_t' wider
+ than 'size_t', which can be a win and conforms to POSIX.
+
+ Won't this cause a problem with objects larger than PTRDIFF_MAX?
+
+ * Typical modern or large platforms do not allocate such objects,
+ so this is not much of a problem in practice; for example, you
+ can safely write 'idx_t len = strlen (s);'. To port to older
+ small platforms where allocations larger than PTRDIFF_MAX could
+ in theory be a problem, you can use Gnulib's ialloc module, or
+ functions like ximalloc in Gnulib's xalloc module.
+
Why not use 'ptrdiff_t' directly?
* Maintainability: When reading and modifying code, it helps to know that