[groff] 07/80: HACKING: Add guidance regarding `\]` in regexes.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit 256eef0bc0fa733cd10b6e10338617d30d712b71
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Fri Nov 22 13:49:02 2024 -0600

    HACKING: Add guidance regarding `\]` in regexes.
---
 HACKING | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/HACKING b/HACKING
index 172a80085..2702eed18 100644
--- a/HACKING
+++ b/HACKING
@@ -175,6 +175,9 @@ Here are some portability notes on writing automated tests.
   in Issue 7 (2018) appears unchanged.
     https://pubs.opengroup.org/onlinepubs/9699919799/utilities/od.html )
 
+* Prior to POSIX.1-2024, the meaning of the sequence `\]` in a basic or
+  extended regular expression is undefined.  Spell it as `]` instead.
+
 * macOS sed requires semicolons after commands even if they are followed
   immediately by a closing brace.