From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 13 Oct 2025 21:56:45 +0000 (-0400)
Subject: Fix incorrect message-printing in win32security.c.
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=03bf7a12c5a44ced377352c8f9bf6e9f4b863885;p=postgresql.git

Fix incorrect message-printing in win32security.c.

log_error() would probably fail completely if used, and would
certainly print garbage for anything that needed to be interpolated
into the message, because it was failing to use the correct printing
subroutine for a va_list argument.

This bug likely went undetected because the error cases this code
is used for are rarely exercised - they only occur when Windows
security API calls fail catastrophically (out of memory, security
subsystem corruption, etc).

The FRONTEND variant can be fixed just by calling vfprintf()
instead of fprintf().  However, there was no va_list variant
of write_stderr(), so create one by refactoring that function.
Following the usual naming convention for such things, call
it vwrite_stderr().

Author: Bryan Green <dbryan.green@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAF+pBj8goe4fRmZ0V3Cs6eyWzYLvK+HvFLYEYWG=TzaM+tWPnw@mail.gmail.com
Backpatch-through: 13
---

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 648d2d2e70c..29643c51439 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -3795,13 +3795,24 @@ write_stderr(const char *fmt,...)
 {
 	va_list		ap;
 
+	va_start(ap, fmt);
+	vwrite_stderr(fmt, ap);
+	va_end(ap);
+}
+
+
+/*
+ * Write errors to stderr (or by equal means when stderr is
+ * not available) - va_list version
+ */
+void
+vwrite_stderr(const char *fmt, va_list ap)
+{
 #ifdef WIN32
 	char		errbuf[2048];	/* Arbitrary size? */
 #endif
 
 	fmt = _(fmt);
-
-	va_start(ap, fmt);
 #ifndef WIN32
 	/* On Unix, we just fprintf to stderr */
 	vfprintf(stderr, fmt, ap);
@@ -3824,5 +3835,4 @@ write_stderr(const char *fmt,...)
 		fflush(stderr);
 	}
 #endif
-	va_end(ap);
 }
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 348dafbf906..001ab93ae6c 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -528,5 +528,6 @@ extern void write_jsonlog(ErrorData *edata);
  * safely (memory context, GUC load etc)
  */
 extern void write_stderr(const char *fmt,...) pg_attribute_printf(1, 2);
+extern void vwrite_stderr(const char *fmt, va_list ap) pg_attribute_printf(1, 0);
 
 #endif							/* ELOG_H */
diff --git a/src/port/win32security.c b/src/port/win32security.c
index a46b82dd048..b7608ab1706 100644
--- a/src/port/win32security.c
+++ b/src/port/win32security.c
@@ -31,9 +31,9 @@ log_error(const char *fmt,...)
 
 	va_start(ap, fmt);
 #ifndef FRONTEND
-	write_stderr(fmt, ap);
+	vwrite_stderr(fmt, ap);
 #else
-	fprintf(stderr, fmt, ap);
+	vfprintf(stderr, fmt, ap);
 #endif
 	va_end(ap);
 }