try to use C99 variadic macros first:
AIX 5.3's XL C has problems with GCC style variadic macros
diff --git a/auto/cc/conf b/auto/cc/conf
index 09ab9d3..bdcce2c 100644
--- a/auto/cc/conf
+++ b/auto/cc/conf
@@ -143,19 +143,6 @@
     . 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 @@
      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
diff --git a/src/core/ngx_log.h b/src/core/ngx_log.h
index b736aa2..1054836 100644
--- a/src/core/ngx_log.h
+++ b/src/core/ngx_log.h
@@ -68,23 +68,7 @@
 
 /*********************************/
 
-#if (NGX_HAVE_GCC_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)
-
-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...)                                    \
-    if ((log)->log_level & level)                                             \
-        ngx_log_error_core(NGX_LOG_DEBUG, log, args)
-
-/*********************************/
-
-#elif (NGX_HAVE_C99_VARIADIC_MACROS)
+#if (NGX_HAVE_C99_VARIADIC_MACROS)
 
 #define NGX_HAVE_VARIADIC_MACROS  1
 
@@ -100,6 +84,22 @@
 
 /*********************************/
 
+#elif (NGX_HAVE_GCC_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)
+
+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...)                                    \
+    if ((log)->log_level & level)                                             \
+        ngx_log_error_core(NGX_LOG_DEBUG, log, args)
+
+/*********************************/
+
 #else /* NO VARIADIC MACROS */
 
 #define NGX_HAVE_VARIADIC_MACROS  0