Add check for compiler variadic macro support in configuration script

acinclude.m4

@@ -1963,3 +1963,67 @@ main()
     dnl if this test fails, configure has already stopped
   fi
 ])
+
+
+dnl CURL_CHECK_VARIADIC_MACROS
+dnl -------------------------------------------------
+dnl Check compiler support of variadic macros
+
+AC_DEFUN([CURL_CHECK_VARIADIC_MACROS], [
+  AC_CACHE_CHECK([for compiler support of C99 variadic macro style],
+    [curl_cv_variadic_macros_c99], [
+    AC_COMPILE_IFELSE([
+      AC_LANG_PROGRAM([
+#define c99_vmacro3(first, ...) fun3(first, __VA_ARGS__)
+#define c99_vmacro2(first, ...) fun2(first, __VA_ARGS__)
+        int fun3(int arg1, int arg2, int arg3);
+        int fun2(int arg1, int arg2);
+        int fun3(int arg1, int arg2, int arg3)
+        { return arg1 + arg2 + arg3; }
+        int fun2(int arg1, int arg2)
+        { return arg1 + arg2; }
+      ],[
+        int res3 = c99_vmacro3(1, 2, 3);
+        int res2 = c99_vmacro2(1, 2);
+      ])
+    ],[
+      curl_cv_variadic_macros_c99="yes"
+    ],[
+      curl_cv_variadic_macros_c99="no"
+    ])
+  ])
+  case "$curl_cv_variadic_macros_c99" in
+    yes)
+      AC_DEFINE_UNQUOTED(HAVE_VARIADIC_MACROS_C99, 1,
+        [Define to 1 if compiler supports C99 variadic macro style.])
+      ;;
+  esac
+  AC_CACHE_CHECK([for compiler support of old gcc variadic macro style],
+    [curl_cv_variadic_macros_gcc], [
+    AC_COMPILE_IFELSE([
+      AC_LANG_PROGRAM([
+#define gcc_vmacro3(first, args...) fun3(first, args)
+#define gcc_vmacro2(first, args...) fun2(first, args)
+        int fun3(int arg1, int arg2, int arg3);
+        int fun2(int arg1, int arg2);
+        int fun3(int arg1, int arg2, int arg3)
+        { return arg1 + arg2 + arg3; }
+        int fun2(int arg1, int arg2)
+        { return arg1 + arg2; }
+      ],[
+        int res3 = c99_vmacro3(1, 2, 3);
+        int res2 = c99_vmacro2(1, 2);
+      ])
+    ],[
+      curl_cv_variadic_macros_gcc="yes"
+    ],[
+      curl_cv_variadic_macros_gcc="no"
+    ])
+  ])
+  case "$curl_cv_variadic_macros_gcc" in
+    yes)
+      AC_DEFINE_UNQUOTED(HAVE_VARIADIC_MACROS_GCC, 1,
+        [Define to 1 if compiler supports old gcc variadic macro style.])
+      ;;
+  esac
+])

configure.ac

@@ -1739,6 +1739,7 @@ dnl default includes
 
 dnl Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST
+CURL_CHECK_VARIADIC_MACROS
 AC_TYPE_SIZE_T
 AC_HEADER_TIME
 CURL_CHECK_STRUCT_TIMEVAL