[nasm:master] preproc: an empty %[] construct generates a null token, drop

[nasm-bot for H. Peter Anvin]

Commit-ID:  baae422e6124000616499629b88cecf9e69dfc55
Gitweb:     http://repo.or.cz/w/nasm.git?a=commitdiff;h=baae422e6124000616499629b88cecf9e69dfc55
Author:     H. Peter Anvin <hpa at zytor.com>
AuthorDate: Mon, 7 Nov 2022 11:47:22 -0800
Committer:  H. Peter Anvin <hpa at zytor.com>
CommitDate: Mon, 7 Nov 2022 11:47:22 -0800

preproc: an empty %[] construct generates a null token, drop

%[] amounts to an empty token; this needs to be handled specially so
that it gets properly dropped.

Fixes: https://bugzilla.nasm.us/show_bug.cgi?id=3392806
Reported-by: C. Masloch <pushbx at ulukai.org>
Signed-off-by: H. Peter Anvin <hpa at zytor.com>


---
 asm/preproc.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/asm/preproc.c b/asm/preproc.c
index cb1669da..a016fda4 100644
--- a/asm/preproc.c
+++ b/asm/preproc.c
@@ -1677,9 +1677,13 @@ static Token *tokenize(const char *line)
 
         if (!ep)
             ep = p;
-        *tail = t = new_Token(NULL, type, line, ep - line);
-        *tok_text_buf(t) = firstchar; /* E.g. %{foo} -> {foo -> %foo */
-        tail = &t->next;
+        toklen = ep - line;
+
+        if (toklen) {
+            *tail = t = new_Token(NULL, type, line, toklen);
+            *tok_text_buf(t) = firstchar; /* E.g. %{foo} -> {foo -> %foo */
+            tail = &t->next;
+        }
 
         line = p;
     }