vim-patch:9.0.0733: use of strftime() is not safe (#21228)

Problem:    Use of strftime() is not safe.
Solution:   Check the return value of strftime().  Use a larger buffer and
            correctly pass the available space. (Dominique Pellé, closes
            vim/vim#11348)

https://github.com/vim/vim/commit/84d14ccdb50dc9f362066a2c83bfaf331314e5ea

Co-authored-by: Dominique Pelle <dominique.pelle@gmail.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/nvim/undo.c b/src/nvim/undo.c
index 0b86a82619..05adc3c6d3 100644
--- a/src/nvim/undo.c
+++ b/src/nvim/undo.c
@@ -2600,12 +2600,16 @@ void undo_fmt_time(char_u *buf, size_t buflen, time_t tt)
   if (time(NULL) - tt >= 100) {
     struct tm curtime;
     os_localtime_r(&tt, &curtime);
+    size_t n;
     if (time(NULL) - tt < (60L * 60L * 12L)) {
       // within 12 hours
-      (void)strftime((char *)buf, buflen, "%H:%M:%S", &curtime);
+      n = strftime((char *)buf, buflen, "%H:%M:%S", &curtime);
     } else {
       // longer ago
-      (void)strftime((char *)buf, buflen, "%Y/%m/%d %H:%M:%S", &curtime);
+      n = strftime((char *)buf, buflen, "%Y/%m/%d %H:%M:%S", &curtime);
+    }
+    if (n == 0) {
+      buf[0] = NUL;
     }
   } else {
     int64_t seconds = time(NULL) - tt;