QGA VSS: Add wrapper to send log to debugger and stderr

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>

qga/vss-win32/meson.build

@@ -7,7 +7,7 @@ link_args = cc.get_supported_link_arguments([
 
 qga_vss = shared_module(
   'qga-vss',
-  ['requester.cpp', 'provider.cpp', 'install.cpp', genh],
+  ['requester.cpp', 'provider.cpp', 'install.cpp', 'vss-debug.cpp', genh],
   name_prefix: '',
   cpp_args: ['-Wno-unknown-pragmas', '-Wno-delete-non-virtual-dtor', '-Wno-non-virtual-dtor'],
   link_args: link_args,

qga/vss-win32/vss-debug.cpp

@@ -0,0 +1,39 @@
+/*
+ * QEMU Guest Agent VSS debug declarations
+ *
+ * Copyright (C) 2023 Red Hat Inc
+ *
+ * Authors:
+ *  Konstantin Kostiuk <kkostiuk@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "vss-debug.h"
+#include "vss-common.h"
+
+void qga_debug_internal(const char *funcname, const char *fmt, ...)
+{
+    char user_string[512] = {0};
+    char full_string[640] = {0};
+
+    va_list args;
+    va_start(args, fmt);
+    if (vsnprintf(user_string, _countof(user_string), fmt, args) <= 0) {
+        va_end(args);
+        return;
+    }
+
+    va_end(args);
+
+    if (snprintf(full_string, _countof(full_string),
+                 QGA_PROVIDER_NAME "[%lu]: %s %s\n",
+                 GetCurrentThreadId(), funcname, user_string) <= 0) {
+        return;
+    }
+
+    OutputDebugString(full_string);
+    fputs(full_string, stderr);
+}

qga/vss-win32/vss-debug.h

@@ -0,0 +1,25 @@
+/*
+ * QEMU Guest Agent VSS debug declarations
+ *
+ * Copyright (C) 2023 Red Hat Inc
+ *
+ * Authors:
+ *  Konstantin Kostiuk <kkostiuk@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include <vss-handles.h>
+
+#ifndef VSS_DEBUG_H
+#define VSS_DEBUG_H
+
+void qga_debug_internal(const char *funcname, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
+
+#define qga_debug(fmt, ...) qga_debug_internal(__func__, fmt, ## __VA_ARGS__)
+#define qga_debug_begin qga_debug("begin")
+#define qga_debug_end qga_debug("end")
+
+#endif