rest-private.h: Use ISO varargs for REST_DEBUG

This way, the code won't be tied to GCC-compatible compilers.  We do, however,
need to enable the more C99-compliant preprocessor that is provided with Visual
Studio 2019 16.8.x or later if we want to build the debugging logging code.

2 files changed, 11 insertions, 2 deletions

diff --git a/meson.build b/meson.build
index 5fb5956..b090c56 100644
--- a/meson.build
+++ b/meson.build
@@ -4,6 +4,15 @@ project('rest', 'c',
   meson_version: '>= 0.56',
 )
 
+cc = meson.get_compiler('c')
+check_cc_args = []
+
+if cc.get_id() == 'msvc'
+  check_cc_args += ['-Zc:preprocessor'] # Use the more C99-compliant preprocessor
+endif
+
+add_project_arguments(cc.get_supported_arguments(check_cc_args), language: ['c'])
+
 # Versioning
 librest_module_version = '0.0.0'
 librest_soversion = '0'
diff --git a/rest/rest-private.h b/rest/rest-private.h
index 6e71322..6a1a716 100644
--- a/rest/rest-private.h
+++ b/rest/rest-private.h
@@ -47,9 +47,9 @@ extern guint rest_debug_flags;
 
 #define REST_DEBUG_ENABLED(category) (rest_debug_flags & REST_DEBUG_##category)
 
-#define REST_DEBUG(category,x,a...)             G_STMT_START {      \
+#define REST_DEBUG(category,x,...)              G_STMT_START {      \
     if (REST_DEBUG_ENABLED(category))                               \
-          { g_message ("[" #category "] " G_STRLOC ": " x, ##a); }  \
+          { g_message ("[" #category "] " G_STRLOC ": " x, ##__VA_ARGS__); }  \
                                                 } G_STMT_END
 
 void _rest_setup_debugging (void);