From 7cf19d055929bbaa37b7195a0abe442a7f20b512 Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Fri, 22 Aug 2025 14:43:48 +0200
Subject: common: Add a wrapper around the W32 OutputDebugString function.

* common/sysutils.c (output_debug_string): New.
---
 common/sysutils.c | 22 ++++++++++++++++++++++
 common/sysutils.h |  2 ++
 2 files changed, 24 insertions(+)

diff --git a/common/sysutils.c b/common/sysutils.c
index 2bacae2ea..2e39d4737 100644
--- a/common/sysutils.c
+++ b/common/sysutils.c
@@ -2007,3 +2007,25 @@ open_stream_nc (gnupg_fd_t fd, const char *mode)
 
   return es_sysopen_nc (&syshd, mode);
 }
+
+
+/* Debug helper to track down problems with logging under Windows.  */
+void
+output_debug_string (const char *format, ...)
+{
+#ifdef HAVE_W32_SYSTEM
+  char *buf;
+  va_list arg_ptr;
+
+  va_start (arg_ptr, format);
+  buf = gpgrt_vbsprintf (format, arg_ptr);
+  va_end (arg_ptr);
+  if (buf)
+    OutputDebugStringA (buf);
+  else
+    OutputDebugStringA ("vbsprintf failed");
+  gpgrt_free (buf);
+#else
+  (void)format;
+#endif
+}
diff --git a/common/sysutils.h b/common/sysutils.h
index 9a90d1018..c832c7932 100644
--- a/common/sysutils.h
+++ b/common/sysutils.h
@@ -121,6 +121,8 @@ int gnupg_inotify_has_name (int fd, const char *name);
 
 estream_t open_stream_nc (gnupg_fd_t fd, const char *mode);
 
+void output_debug_string (const char *format, ...) GPGRT_ATTR_PRINTF(1,2);
+
 #ifdef HAVE_W32_SYSTEM
 int gnupg_w32_set_errno (int ec);
 void *w32_get_user_sid (void);
-- 
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