From 887d3a1bbcf79c692923d98f8b584b32a50daebd Mon Sep 17 00:00:00 2001
From: Evan Miller <emmiller@gmail.com>
Date: Sun, 18 Feb 2024 14:44:23 -0500
Subject: [PATCH] [SAV reader] force parse error if attempting to decrement
 zero

---
 src/spss/readstat_sav_read.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/spss/readstat_sav_read.c b/src/spss/readstat_sav_read.c
index 460bf07..d36bab9 100644
--- a/src/spss/readstat_sav_read.c
+++ b/src/spss/readstat_sav_read.c
@@ -717,7 +717,11 @@ static readstat_error_t sav_process_row(unsigned char *buffer, size_t buffer_len
             }
             if (++offset == col_info->width) {
                 if (++segment_offset < var_info->n_segments) {
-                    if (raw_str_used > 0) raw_str_used--;
+                    if (raw_str_used == 0) {
+                        retval = READSTAT_ERROR_PARSE;
+                        goto done;
+                    }
+                    raw_str_used--;
                 }
                 offset = 0;
                 col++;