From 3c083484a3594f3c4e72fc06c001418a67dfe71a Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Mon, 2 Jan 2006 22:20:21 +0300
Subject: [PATCH] implement #strong_define

Example

	#strong_define FOO 1

	#undef	FOO	// silently ignored
	#define	FOO 2	// silently ignored

This allows (for example) to override CONFIG_XXX values without
editing include/linux/autoconf.h

I think this is useful. If you think differently, I will appreciate
your comments on this patch correctness.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
---
 pre-process.c | 28 +++++++++++++++++-----------
 symbol.h      |  7 ++++---
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/pre-process.c b/pre-process.c
index 604b101a..0fb7831d 100644
--- a/pre-process.c
+++ b/pre-process.c
@@ -1092,7 +1092,7 @@ static int do_handle_define(struct stream *stream, struct token **line, struct t
 	if (sym) {
 		int clean;
 
-		if (attr > sym->attr)
+		if (attr < sym->attr)
 			goto out;
 
 		clean = (attr == sym->attr);
@@ -1138,6 +1138,11 @@ static int handle_weak_define(struct stream *stream, struct token **line, struct
 	return do_handle_define(stream, line, token, SYM_ATTR_WEAK);
 }
 
+static int handle_strong_define(struct stream *stream, struct token **line, struct token *token)
+{
+	return do_handle_define(stream, line, token, SYM_ATTR_STRONG);
+}
+
 static int handle_undef(struct stream *stream, struct token **line, struct token *token)
 {
 	struct token *left = token->next;
@@ -1149,7 +1154,7 @@ static int handle_undef(struct stream *stream, struct token **line, struct token
 	}
 
 	sym = lookup_macro(left->ident);
-	if (!sym)
+	if (!sym || sym->attr > SYM_ATTR_NORMAL)
 		return 1;
 
 	if (sym->scope != file_scope) {
@@ -1569,15 +1574,16 @@ static void init_preprocessor(void)
 		const char *name;
 		int (*handler)(struct stream *, struct token **, struct token *);
 	} normal[] = {
-		{ "define",	handle_define },
-		{ "weak_define",handle_weak_define },
-		{ "undef",	handle_undef },
-		{ "warning",	handle_warning },
-		{ "error",	handle_error },
-		{ "include",	handle_include },
-		{ "include_next",handle_include_next },
-		{ "pragma",	handle_pragma },
-		{ "line",	handle_line },
+		{ "define",		handle_define },
+		{ "weak_define",	handle_weak_define },
+		{ "strong_define",	handle_strong_define },
+		{ "undef",		handle_undef },
+		{ "warning",		handle_warning },
+		{ "error",		handle_error },
+		{ "include",		handle_include },
+		{ "include_next",	handle_include_next },
+		{ "pragma",		handle_pragma },
+		{ "line",		handle_line },
 
 		// our internal preprocessor tokens
 		{ "nostdinc",	   handle_nostdinc },
diff --git a/symbol.h b/symbol.h
index 0803710d..91cc06ac 100644
--- a/symbol.h
+++ b/symbol.h
@@ -82,13 +82,14 @@ struct symbol_op {
 extern int expand_safe_p(struct expression *expr, int cost);
 extern int expand_constant_p(struct expression *expr, int cost);
 
-#define SYM_ATTR_WEAK		1
-#define SYM_ATTR_NORMAL		0
+#define SYM_ATTR_WEAK		0
+#define SYM_ATTR_NORMAL		1
+#define SYM_ATTR_STRONG		2
 
 struct symbol {
 	enum namespace namespace:8;
 	enum type type:8;
-	unsigned char used:1, attr:1;
+	unsigned char used:1, attr:2;
 	struct position pos;		/* Where this symbol was declared */
 	struct ident *ident;		/* What identifier this symbol is associated with */
 	struct symbol *next_id;		/* Next semantic symbol that shares this identifier */
-- 
2.11.4.GIT