bug#20258: 24.5; format-time-string miscounting of multibyte characters

[Lars Ingebrigtsen <larsi@gnus.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> The POSIX descriptions says bytes.
>
> Right.  So it might be a glibc documentation bug (or maybe the glibc
> manual I have here is outdated).
>
> And there is the issue with non-glibc implementations.

What about something appropriately vague like the following patch to
draw attention to the issue:

diff --git a/src/timefns.c b/src/timefns.c
index 330d5623f0..20f7ccb7d7 100644
--- a/src/timefns.c
+++ b/src/timefns.c
@@ -1437,8 +1437,11 @@ DEFUN ("format-time-string", Fformat_time_string, Sformat_time_string, 1, 3, 0,
 `^' Use upper case characters if possible.
 `#' Use opposite case characters if possible.
 
-A field width N is an unsigned decimal integer with a leading digit nonzero.
-%NX is like %X, but takes up at least N positions.
+A field width N is an unsigned decimal integer with a leading digit
+nonzero.  %NX is like %X, but takes up at least N positions.  The
+field width is (on most systems) in bytes, not characters, so it
+depends on the locale what the width (in characters) %NX will end up
+being.
 
 The modifiers are:
 


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