From d6c55de1f99a9028540516316b95321a7b12a540 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 26 Sep 2018 13:31:56 -0400 Subject: 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 --- src/backend/lib/stringinfo.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'src/backend/lib/stringinfo.c') diff --git a/src/backend/lib/stringinfo.c b/src/backend/lib/stringinfo.c index 798a823ac9f..df7e01f76d9 100644 --- a/src/backend/lib/stringinfo.c +++ b/src/backend/lib/stringinfo.c @@ -77,12 +77,15 @@ resetStringInfo(StringInfo str) void appendStringInfo(StringInfo str, const char *fmt,...) { + int save_errno = errno; + for (;;) { va_list args; int needed; /* Try to format the data. */ + errno = save_errno; va_start(args, fmt); needed = appendStringInfoVA(str, fmt, args); va_end(args); @@ -105,6 +108,9 @@ appendStringInfo(StringInfo str, const char *fmt,...) * pass the return value to enlargeStringInfo() before trying again; see * appendStringInfo for standard usage pattern. * + * Caution: callers must be sure to preserve their entry-time errno + * when looping, in case the fmt contains "%m". + * * XXX This API is ugly, but there seems no alternative given the C spec's * restrictions on what can portably be done with va_list arguments: you have * to redo va_start before you can rescan the argument list, and we can't do -- cgit v1.2.3