[PATCH] sparse: add support for __VA_OPT__

The linux kernel has started using __VA_OPT__ so lets add support for it.

What it does is it adds an optional thing, normally a comma, if the
__VA_ARGS__ parameter is not empty.  So if you have at least one argument
but possibly more then you could create a macro like:

#define test_args(a, ...) printf(a __VA_OPT__(,) __VA_ARGS__)

If you call test_args("foo\n") it expands to:

printf("foo\n");

but if you pass two arguments test_args("foo %d\n", 2) it expands to:

printf("foo\n" , 2);

I guess if you wanted instead of a comma then you could have an empty
__VA_OPT__() or you could pass random things like __VA_OPT__(a b c).  I
don't know why you would do that.  In this case, "a" is a macro argument
so that has to be expanded out.

Signed-off-by: Dan Carpenter <[email protected]>
---
 ident-list.h  |  1 +
 pre-process.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/ident-list.h b/ident-list.h
index d65668108385..bffc4038a75d 100644
--- a/ident-list.h
+++ b/ident-list.h
@@ -66,6 +66,7 @@ IDENT(c_static_assert);
 __IDENT(pragma_ident, "__pragma__", 0);
 __IDENT(_Pragma_ident, "_Pragma", 0);
 __IDENT(__VA_ARGS___ident, "__VA_ARGS__", 0);
+__IDENT(__VA_OPT___ident, "__VA_OPT__", 0);
 __IDENT(__func___ident, "__func__", 0);
 __IDENT(__FUNCTION___ident, "__FUNCTION__", 0);
 __IDENT(__PRETTY_FUNCTION___ident, "__PRETTY_FUNCTION__", 0);
diff --git a/pre-process.c b/pre-process.c
index 05a5a79396a8..94710301ce17 100644
--- a/pre-process.c
+++ b/pre-process.c
@@ -643,11 +643,49 @@ static int handle_kludge(struct token **p, struct arg *args)
 	}
 }
 
+static struct token *get_VA_OPT(struct token **p, struct arg *args)
+{
+	struct token *t = (*p)->next;
+	const char *expected;
+	struct token *ret = NULL;
+	struct token *dup, *tail;
+
+	if (token_type(t) != TOKEN_SPECIAL || t->special != '(') {
+		expected = "(";
+		goto error;
+	}
+	while (true) {
+		t = t->next;
+		if (eof_token(t)) {
+			expected = ")";
+			goto error;
+		}
+		if (token_type(t) == TOKEN_SPECIAL &&
+		    t->special == ')')
+			break;
+		dup = dup_token(t, &(*p)->pos);
+		if (!ret)
+			ret = dup;
+		else
+			tail->next = dup;
+		tail = dup;
+	}
+
+	if (tail)
+		tail->next = &eof_token_entry;
+	*p = t;
+	return ret;
+error:
+	sparse_error(t->pos, "__VA_OPT__ error: expected '%s'", expected);
+	return NULL;
+}
+
 static struct token **substitute(struct token **list, struct token *body, struct arg *args)
 {
 	struct position *base_pos = &(*list)->pos;
 	int *count;
 	enum {Normal, Placeholder, Concat} state = Normal;
+	struct token *va_opt = NULL;
 
 	for (; !eof_token(body); body = body->next) {
 		struct token *added, *arg;
@@ -697,6 +735,10 @@ static struct token **substitute(struct token **list, struct token *body, struct
 
 		case TOKEN_MACRO_ARGUMENT:
 			arg = args[body->argnum].expanded;
+			if (va_opt && !eof_token(arg)) {
+				list = substitute(list, va_opt, args);
+				va_opt = NULL;
+			}
 			count = &args[body->argnum].n_normal;
 			if (eof_token(arg)) {
 				state = Normal;
@@ -716,6 +758,11 @@ static struct token **substitute(struct token **list, struct token *body, struct
 			continue;
 
 		case TOKEN_IDENT:
+			if (body->ident == &__VA_OPT___ident) {
+				va_opt = get_VA_OPT(&body, args);
+				continue;
+			}
+
 			added = dup_token(body, base_pos);
 			if (added->ident->tainted)
 				added->pos.noexpand = 1;
@@ -1234,6 +1281,8 @@ static struct token *parse_arguments(struct token *list)
 	while (token_type(arg) == TOKEN_IDENT) {
 		if (arg->ident == &__VA_ARGS___ident)
 			goto Eva_args;
+		if (arg->ident == &__VA_OPT___ident)
+			goto Eva_opt;
 		if (!++count->normal)
 			goto Eargs;
 		next = arg->next;
@@ -1312,6 +1361,9 @@ Enotclosed:
 Eva_args:
 	sparse_error(arg->pos, "__VA_ARGS__ can only appear in the expansion of a C99 variadic macro");
 	return NULL;
+Eva_opt:
+	sparse_error(arg->pos, "__VA_OPT__ can only appear in the expansion of a C99 variadic macro");
+	return NULL;
 Eargs:
 	sparse_error(arg->pos, "too many arguments in macro definition");
 	return NULL;
-- 
2.51.0