Don't re-expand macro if current macro is unnamed

pnut.c

@@ -1660,8 +1660,11 @@ void begin_macro_expansion(int ident, int tokens, int args) {
 // Search the macro stack to see if the macro is already expanding.
 bool macro_is_already_expanding(int ident) {
   int i = macro_stack_ix;
-  if (ident == 0 || macro_ident == 0) return false; // Unnamed macro or no macro is expanding
-  if (ident == macro_ident)           return true;  // The same macro is already expanding
+  // Unnamed macro (i.e. replaying tokens or playing a macro argument)
+  if (ident == 0)           return false;
+
+  // The macro is currently expanding
+  if (ident == macro_ident) return true;
 
   // Traverse the stack to see if the macro is already expanding
   while (i > 0) {

tests/_all/preprocessor/macro/self-reference.c

@@ -1,7 +1,7 @@
 // tests for recursion depth of macros
 
-// putchar
 #include <stdio.h>
+#include <stdlib.h>
 
 int test1 = 1;
 int test2 = 2;
@@ -33,7 +33,21 @@ void B(int a, int b) {
 #define B(a1, a2) C(a1, a2)
 #define C(a1, a2) B(a1, a2)
 
+struct STATE {
+  int regA;
+  int regB;
+};
+
+struct STATE *global_state;
+
+#define struct_field(sym) global_state->sym
+#define regA              struct_field(regA)
+
 void main() {
+  global_state = malloc(sizeof (struct STATE));
+  regA = 'A';
+  putchar(regA); putchar('\n');
+
   putdigit(test1);
   putdigit(test2);
   putdigit(test3);

tests/_all/preprocessor/macro/self-reference.golden

@@ -1,3 +1,4 @@
+A
 1
 2
 3