GNU bug report logs - #32252
[PATCH] %o and %x now format signed numbers

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Helmut Eller <eller.helmut <at> gmail.com>
Cc: 32252 <at> debbugs.gnu.org
Subject: bug#32252: [PATCH] %o and %x now format signed numbers
Date: Mon, 23 Jul 2018 16:39:08 -0700

> Why breaking longstanding behavior instead of introducing this with a
> different format specifier.  Like %a.

Although it is indeed an incompatible change, I surveyed the existing 
Emacs source code and couldn't find anything that the change would 
break. Almost all uses of %x, %X, and %o were with nonnegative integers 
where the behavior would not change. In the few places I found where the 
integers could be negative, the resulting strings were things like 
nonces where the change didn't break anything. Of course I could have 
missed some uses, and there are uses outside of Emacs source code; 
still, it seems that this change would break very little user code (and 
the rare users who might run into a problem have a simple workaround).

%a has quite a different meaning in C11, so we'd need to use some other 
letter (or set of letters, if we want something for %x, %X, %o) if we 
went that route. This seems like overkill for such a small change to 
functionality that hardly ever matters; plus, %x, %X and %o would 
continue to have problematic machine-dependent semantics and would not 
be sensibly extensible to bignums.

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