[PATCH 08/20] pre-process: Avoid zero-length VLAs for parameterless macros

[Bart Van Assche <bvanassche@acm.org>]

Ensure at least one element when declaring the variable-length args[]
arrays in expand() and dump_macro() by using nargs ? nargs : 1 instead of
nargs.

Avoid undefined behavior in C from declaring zero-length variable-length
arrays on the stack when expanding or dumping function-like macros defined
with an empty parameter list (nargs == 0).

Fixes: 669244d22464 ("[PATCH] lazy-copy macro expansion in pre-processing")
Fixes: 9b4e30eb0baf ("teach sparse how to dump macro definitions")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 pre-process.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pre-process.c b/pre-process.c
index 4e322855d600..038e019b11c9 100644
--- a/pre-process.c
+++ b/pre-process.c
@@ -745,7 +745,7 @@ static int expand(struct token **list, struct symbol *sym)
 	struct token **tail;
 	struct token *expansion = sym->expansion;
 	int nargs = sym->arglist ? sym->arglist->count.normal : 0;
-	struct arg args[nargs];
+	struct arg args[nargs ? nargs : 1];
 
 	if (expanding->tainted) {
 		token->pos.noexpand = 1;
@@ -2285,7 +2285,7 @@ static int is_VA_ARGS_token(struct token *token)
 static void dump_macro(struct symbol *sym)
 {
 	int nargs = sym->arglist ? sym->arglist->count.normal : 0;
-	struct token *args[nargs];
+	struct token *args[nargs ? nargs : 1];
 	struct token *token;
 
 	printf("#define %s", show_ident(sym->ident));