Warn about undefined preprocessor symbols at expansion time, not parse time

This means that we can do

	#if defined(TOKEN) && TOKEN > 1

and we will _not_ warn even with -Wundef, since the "TOKEN > 1" test
will never even be expanded if TOKEN isn't defined.

Al Viro gets credit for the algorithm changes, I just did the actual coding.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/expression.c b/expression.c
index 310aa17..0a79581 100644
--- a/expression.c
+++ b/expression.c
@@ -301,6 +301,15 @@ struct token *primary_expression(struct token *token, struct expression **tree)
 		token = token->next;
 		break;
 
+	case TOKEN_ZERO_IDENT: {
+		expr = alloc_expression(token->pos, EXPR_SYMBOL);
+		expr->ctype = &int_ctype;
+		expr->symbol = &zero_int;
+		expr->symbol_name = token->ident;
+		token = token->next;
+		break;
+	}
+
 	case TOKEN_IDENT: {
 		struct symbol *sym = lookup_symbol(token->ident, NS_SYMBOL | NS_TYPEDEF);
 		struct token *next = token->next;