From 533aeb1dfa508e00ccc9acc375140e9f9b81eb41 Mon Sep 17 00:00:00 2001
From: Jeremiah Orians <jeremiah@pdp10.guru>
Date: Thu, 20 Jan 2022 07:38:01 -0500
Subject: [PATCH] nested #if blocks now behave correctly

---
 cc_macro.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/cc_macro.c b/cc_macro.c
index 6e44139..4f493ca 100644
--- a/cc_macro.c
+++ b/cc_macro.c
@@ -808,6 +808,38 @@ struct token_list* expand_macro_functions(struct token_list* expansion, struct t
 	return hold;
 }
 
+void eat_until_endif()
+{
+	/* This #if block is nested inside of an #if block that needs to be dropped, lose EVERYTHING */
+	do
+	{
+		if(match("#if", macro_token->s) || match("#ifdef", macro_token->s) || match("#ifndef", macro_token->s))
+		{
+			eat_current_token();
+			eat_until_endif();
+		}
+
+		eat_current_token();
+		require(NULL != macro_token, "Unterminated #if block\n");
+	} while(!match("#endif", macro_token->s));
+}
+
+void eat_block()
+{
+	/* This conditional #if block is wrong, drop everything until the #elif/#else/#endif */
+	do
+	{
+		if(match("#if", macro_token->s) || match("#ifdef", macro_token->s) || match("#ifndef", macro_token->s))
+		{
+			eat_current_token();
+			eat_until_endif();
+		}
+
+		eat_current_token();
+		require(NULL != macro_token, "Unterminated #if block\n");
+	} while(!match("#elif", macro_token->s) && !match("#else", macro_token->s) && !match("#endif", macro_token->s));
+}
+
 struct token_list* maybe_expand(struct token_list* token)
 {
 	if(NULL == token)
@@ -919,7 +951,8 @@ void preprocess()
 			else if(!conditional_inclusion_top->include)
 			{
 				/* rewrite the token stream to exclude the current token */
-				eat_current_token();
+				eat_block();
+				start_of_line = TRUE;
 			}
 			else
 			{