a nested macro expansion, additional case

    fixed segfaul for the case
    #define A B;
    #define B A
    return A + B;

    But fix is not perfect. tcc and gcc outputs differs for
    #define A B + 1;
    #define B A
    return A + B;

tccpp.c

@@ -3702,11 +3702,17 @@ static void macro_subst(
 
             /* if nested substitution, do nothing */
             s2 = sym_find2(*nested_list, t);
-            if (s2 && s2->c) {
-                /* and mark it as TOK_NOSUBST, so it doesn't get subst'd again */
-                tok_str_add2(tok_str, TOK_NOSUBST, NULL);
-                goto no_subst;
+            if (s2) {
+                if (s2->c || s->asm_label) {
+                    /* and mark it as TOK_NOSUBST, so it doesn't get subst'd again */
+                    s->asm_label = 0;
+                    tok_str_add2(tok_str, TOK_NOSUBST, NULL);
+                    goto no_subst;
+                }
+                s->asm_label++;
             }
+            else
+                s->asm_label = 0;
 
             {
                 TokenString str;

tests/pp/15.c

@@ -1,3 +1,17 @@
 #define Y(x) Z(x)
 #define X Y
 X(X(1))
+
+#define A B
+#define B A
+return A + B;
+
+#if 0
+#undef A
+#undef B
+
+#define A 1 + B
+#define B A
+return A + B;
+// currently output of the gcc and tcc differs
+#endif

tests/pp/15.expect

@@ -1 +1,2 @@
 Z(Z(1))
+return A + B;