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/interfaces/libpq/pqexpbuffer.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'src/interfaces/libpq/pqexpbuffer.c') diff --git a/src/interfaces/libpq/pqexpbuffer.c b/src/interfaces/libpq/pqexpbuffer.c index 0814ec6dbe0..43c36c3bff8 100644 --- a/src/interfaces/libpq/pqexpbuffer.c +++ b/src/interfaces/libpq/pqexpbuffer.c @@ -233,6 +233,7 @@ enlargePQExpBuffer(PQExpBuffer str, size_t needed) void printfPQExpBuffer(PQExpBuffer str, const char *fmt,...) { + int save_errno = errno; va_list args; bool done; @@ -244,6 +245,7 @@ printfPQExpBuffer(PQExpBuffer str, const char *fmt,...) /* Loop in case we have to retry after enlarging the buffer. */ do { + errno = save_errno; va_start(args, fmt); done = appendPQExpBufferVA(str, fmt, args); va_end(args); @@ -261,6 +263,7 @@ printfPQExpBuffer(PQExpBuffer str, const char *fmt,...) void appendPQExpBuffer(PQExpBuffer str, const char *fmt,...) { + int save_errno = errno; va_list args; bool done; @@ -270,6 +273,7 @@ appendPQExpBuffer(PQExpBuffer str, const char *fmt,...) /* Loop in case we have to retry after enlarging the buffer. */ do { + errno = save_errno; va_start(args, fmt); done = appendPQExpBufferVA(str, fmt, args); va_end(args); @@ -281,6 +285,9 @@ appendPQExpBuffer(PQExpBuffer str, const char *fmt,...) * Shared guts of printfPQExpBuffer/appendPQExpBuffer. * Attempt to format data and append it to str. Returns true if done * (either successful or hard failure), false if need to retry. + * + * Caution: callers must be sure to preserve their entry-time errno + * when looping, in case the fmt contains "%m". */ static bool appendPQExpBufferVA(PQExpBuffer str, const char *fmt, va_list args) -- cgit v1.2.3