try to use C99 variadic macros first:

AIX 5.3's XL C has problems with GCC style variadic macros

auto/cc/conf

@@ -143,19 +143,6 @@ if [ "$NGX_PLATFORM" != win32 ]; then
     . auto/feature
 
 
-    ngx_feature="gcc variadic macros"
-    ngx_feature_name="NGX_HAVE_GCC_VARIADIC_MACROS"
-    ngx_feature_run=yes
-    ngx_feature_incs="#include <stdio.h>
-#define var(dummy, args...)  sprintf(args)"
-    ngx_feature_path=
-    ngx_feature_libs=
-    ngx_feature_test="char  buf[30]; buf[0] = '0';
-                      var(0, buf, \"%d\", 1);
-                      if (buf[0] != '1') return 1"
-    . auto/feature
-
-
     if [ "$NGX_CC_NAME" = "ccc" ]; then
         echo "checking for C99 variadic macros ... disabled"
     else
@@ -173,6 +160,19 @@ if [ "$NGX_PLATFORM" != win32 ]; then
      fi
 
 
+    ngx_feature="gcc variadic macros"
+    ngx_feature_name="NGX_HAVE_GCC_VARIADIC_MACROS"
+    ngx_feature_run=yes
+    ngx_feature_incs="#include <stdio.h>
+#define var(dummy, args...)  sprintf(args)"
+    ngx_feature_path=
+    ngx_feature_libs=
+    ngx_feature_test="char  buf[30]; buf[0] = '0';
+                      var(0, buf, \"%d\", 1);
+                      if (buf[0] != '1') return 1"
+    . auto/feature
+
+
 #    ngx_feature="inline"
 #    ngx_feature_name=
 #    ngx_feature_run=no

src/core/ngx_log.h

@@ -68,35 +68,35 @@ struct ngx_log_s {
 
 /*********************************/
 
-#if (NGX_HAVE_GCC_VARIADIC_MACROS)
+#if (NGX_HAVE_C99_VARIADIC_MACROS)
 
 #define NGX_HAVE_VARIADIC_MACROS  1
 
-#define ngx_log_error(level, log, args...)                                    \
-    if ((log)->log_level >= level) ngx_log_error_core(level, log, args)
+#define ngx_log_error(level, log, ...)                                        \
+    if ((log)->log_level >= level) ngx_log_error_core(level, log, __VA_ARGS__)
 
 void ngx_log_error_core(ngx_uint_t level, ngx_log_t *log, ngx_err_t err,
     const char *fmt, ...);
 
-#define ngx_log_debug(level, log, args...)                                    \
+#define ngx_log_debug(level, log, ...)                                        \
     if ((log)->log_level & level)                                             \
-        ngx_log_error_core(NGX_LOG_DEBUG, log, args)
+        ngx_log_error_core(NGX_LOG_DEBUG, log, __VA_ARGS__)
 
 /*********************************/
 
-#elif (NGX_HAVE_C99_VARIADIC_MACROS)
+#elif (NGX_HAVE_GCC_VARIADIC_MACROS)
 
 #define NGX_HAVE_VARIADIC_MACROS  1
 
-#define ngx_log_error(level, log, ...)                                        \
-    if ((log)->log_level >= level) ngx_log_error_core(level, log, __VA_ARGS__)
+#define ngx_log_error(level, log, args...)                                    \
+    if ((log)->log_level >= level) ngx_log_error_core(level, log, args)
 
 void ngx_log_error_core(ngx_uint_t level, ngx_log_t *log, ngx_err_t err,
     const char *fmt, ...);
 
-#define ngx_log_debug(level, log, ...)                                        \
+#define ngx_log_debug(level, log, args...)                                    \
     if ((log)->log_level & level)                                             \
-        ngx_log_error_core(NGX_LOG_DEBUG, log, __VA_ARGS__)
+        ngx_log_error_core(NGX_LOG_DEBUG, log, args)
 
 /*********************************/