From 103c29e634d822e0affd7d3ae16a7d8a80c038d3 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Thu, 13 Jan 2022 15:38:56 +0100
Subject: Fix tonumber("-0") in dual-number mode.

Reported by Sergey Kaplun.
---
 src/lj_strscan.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/lj_strscan.c b/src/lj_strscan.c
index ccf74860..d18fab8c 100644
--- a/src/lj_strscan.c
+++ b/src/lj_strscan.c
@@ -121,7 +121,8 @@ static StrScanFmt strscan_hex(const uint8_t *p, TValue *o,
   /* Format-specific handling. */
   switch (fmt) {
   case STRSCAN_INT:
-    if (!(opt & STRSCAN_OPT_TONUM) && x < 0x80000000u+neg) {
+    if (!(opt & STRSCAN_OPT_TONUM) && x < 0x80000000u+neg &&
+	!(x == 0 && neg)) {
       o->i = neg ? -(int32_t)x : (int32_t)x;
       return STRSCAN_INT;  /* Fast path for 32 bit integers. */
     }
@@ -448,6 +449,9 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
       if ((opt & STRSCAN_OPT_TONUM)) {
 	o->n = neg ? -(double)x : (double)x;
 	return STRSCAN_NUM;
+      } else if (x == 0 && neg) {
+	o->n = -0.0;
+	return STRSCAN_NUM;
       } else {
 	o->i = neg ? -(int32_t)x : (int32_t)x;
 	return STRSCAN_INT;
@@ -463,7 +467,7 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
       fmt = strscan_dec(sp, o, fmt, opt, ex, neg, dig);
 
     /* Try to convert number to integer, if requested. */
-    if (fmt == STRSCAN_NUM && (opt & STRSCAN_OPT_TOINT)) {
+    if (fmt == STRSCAN_NUM && (opt & STRSCAN_OPT_TOINT) && !tvismzero(o)) {
       double n = o->n;
       int32_t i = lj_num2int(n);
       if (n == (lua_Number)i) { o->i = i; return STRSCAN_INT; }
-- 
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