Implement %m in src/port/snprintf.c, and teach elog.c to rely on that.

I started out with the idea that we needed to detect use of %m format specs
in contexts other than elog/ereport calls, because we couldn't rely on that
working in *printf calls.  But a better answer is to fix things so that it
does work.  Now that we're using snprintf.c all the time, we can implement
%m in that and we've fixed the problem.

This requires also adjusting our various printf-wrapping functions so that
they ensure "errno" is preserved when they call snprintf.c.

Remove elog.c's handmade implementation of %m, and let it rely on
snprintf to support the feature.  That should provide some performance
gain, though I've not attempted to measure it.

There are a lot of places where we could now simplify 'printf("%s",
strerror(errno))' into 'printf("%m")', but I'm not in any big hurry
to make that happen.

Patch by me, reviewed by Michael Paquier

Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us

1 files changed, 2 insertions, 0 deletions

diff --git a/src/pl/plpython/plpy_elog.c b/src/pl/plpython/plpy_elog.c
index e244104fed..3814a6c32d 100644
--- a/src/pl/plpython/plpy_elog.c
+++ b/src/pl/plpython/plpy_elog.c
@@ -46,6 +46,7 @@ static bool set_string_attr(PyObject *obj, char *attrname, char *str);
 void
 PLy_elog_impl(int elevel, const char *fmt,...)
 {
+	int			save_errno = errno;
 	char	   *xmsg;
 	char	   *tbmsg;
 	int			tb_depth;
@@ -96,6 +97,7 @@ PLy_elog_impl(int elevel, const char *fmt,...)
 			va_list		ap;
 			int			needed;
 
+			errno = save_errno;
 			va_start(ap, fmt);
 			needed = appendStringInfoVA(&emsg, dgettext(TEXTDOMAIN, fmt), ap);
 			va_end(ap);