[nasm:master] preproc: add warning for empty %{} construct

[nasm-bot for H. Peter Anvin]

Commit-ID:  7b8cd67d5165320cf95fa6906654751a30817c96
Gitweb:     http://repo.or.cz/w/nasm.git?a=commitdiff;h=7b8cd67d5165320cf95fa6906654751a30817c96
Author:     H. Peter Anvin <hpa at zytor.com>
AuthorDate: Mon, 7 Nov 2022 12:01:00 -0800
Committer:  H. Peter Anvin <hpa at zytor.com>
CommitDate: Mon, 7 Nov 2022 12:01:00 -0800

preproc: add warning for empty %{} construct

An empty %{} becomes % which is simply the arithmetic
operator. Although that is consistent, it might be surprising for
users, to issue a warning.

Signed-off-by: H. Peter Anvin <hpa at zytor.com>


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

diff --git a/asm/preproc.c b/asm/preproc.c
index a016fda4..99218250 100644
--- a/asm/preproc.c
+++ b/asm/preproc.c
@@ -1397,6 +1397,9 @@ static Token *tokenize(const char *line)
             /* Classify here, to handle %{...} correctly */
             if (toklen < 2) {
                 type = '%';     /* % operator */
+                if (unlikely(*line == '{')) {
+                    nasm_warn(WARN_OTHER, "empty %%{} construct treated like the %% arithmetric operator");
+                }
             } else {
                 char c0 = line[1];