Fix macro expansion of empty args.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

tccpp.c

@@ -2640,7 +2640,7 @@ static int *macro_arg_subst(Sym **nested_list, const int *macro_str, Sym *args)
                             tok_str_add2(&str, t1, &cval);
                         }
                     }
-                } else {
+                } else if (*st != TOK_PLCHLDR) {
                     /* NOTE: the stream cannot be read when macro
                        substituing an argument */
                     macro_subst(&str, nested_list, st, NULL);

tests/tests2/71_macro_empty_arg.c

@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+#define T(a,b,c) a b c
+
+int main(void)
+{
+    printf("%d", T(1,+,2) T(+,,) T(,2,*) T(,7,) T(,,));
+    return 0;
+}

tests/tests2/71_macro_empty_arg.expect

@@ -0,0 +1 @@
+17

tests/tests2/Makefile

@@ -89,7 +89,9 @@ TESTS =	\
  67_macro_concat.test \
  68_macro_param_list_err_1.test \
  69_macro_param_list_err_2.test \
- 70_floating_point_literals.test
+ 70_floating_point_literals.test \
+ 71_macro_empty_arg.test \
+
 
 # 34_array_assignment.test -- array assignment is not in C standard