doc: update re. ISO C23 printf changes

The new `%w99d` fixed-width modifier still needs work in `frr-format`, which unfortunately is not as trivial as `%b` was. Signed-off-by: David Lamparter <[email protected]>
FRRouting · Mar 10, 2024 · 9ae4dd3 · 9ae4dd3
1 parent f436dc0
commit 9ae4dd3
Showing 1 changed file with 11 additions and 3 deletions.
diff --git a/doc/developer/logging.rst b/doc/developer/logging.rst
@@ -77,7 +77,14 @@ are available:
 
 .. note::
 
-   ``printfrr()`` does not support the ``%n`` format.
+   ``printfrr()`` does not support the ``%n`` format.  It does support ISO C23
+   ``%b``, ``%w99d`` and ``%wf99d`` additions, but the latter two are not
+   supported by the ``frr-format`` plugin yet, and all 3 aren't supported by
+   the older compilers still in use on some supported platforms.
+
+   ``%b`` can be used with ``FMT_NSTD``, but ``%w99d`` and ``%wf99d`` require
+   work in the ``frr-format`` plugin before they are really usable.
+
 
 AS-Safety
 ^^^^^^^^^
@@ -557,8 +564,9 @@ Integer formats
    cause compiler warnings when used without the plugin.  Use with
    :c:macro:`FMT_NSTD` if necessary.
 
-   It is possible ISO C23 may introduce another format for these, possibly
-   ``%w64d`` discussed in `JTC 1/SC 22/WG 14/N2680 <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2680.pdf>`_.
+   As anticipated, ISO C23 has introduced new modifiers for this, specifically
+   ``%w64d`` (= ``%Ld``) and ``%w64u`` (= ``%Lu``).  Unfortunately, these new
+   modifiers are not supported by ``frr-format`` yet.
 
 .. frrfmt:: %Lu (uint64_t)