From 2651448084a56dd0b960989798772e71e12e6c30 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Thu, 20 Aug 2020 19:36:49 +0900
Subject: [PATCH] Expand macros in the #if and #elif argument context

---
 preprocess.c |  3 +++
 test/macro.c | 16 ++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/preprocess.c b/preprocess.c
index ba6985a..e67f324 100644
--- a/preprocess.c
+++ b/preprocess.c
@@ -20,6 +20,8 @@ struct CondIncl {
 static Macro *macros;
 static CondIncl *cond_incl;
 
+static Token *preprocess2(Token *tok);
+
 static bool is_hash(Token *tok) {
   return tok->at_bol && equal(tok, "#");
 }
@@ -113,6 +115,7 @@ static Token *copy_line(Token **rest, Token *tok) {
 static long eval_const_expr(Token **rest, Token *tok) {
   Token *start = tok;
   Token *expr = copy_line(rest, tok->next);
+  expr = preprocess2(expr);
 
   if (expr->kind == TK_EOF)
     error_tok(start, "no expression");
diff --git a/test/macro.c b/test/macro.c
index 6481464..61447f6 100644
--- a/test/macro.c
+++ b/test/macro.c
@@ -128,6 +128,22 @@ int main() {
 
   if (0);
 
+#define M 5
+#if M
+  m = 5;
+#else
+  m = 6;
+#endif
+  assert(5, m, "m");
+
+#define M 5
+#if M-5
+  m = 6;
+#elif M
+  m = 5;
+#endif
+  assert(5, m, "m");
+
   printf("OK\n");
   return 0;
 }