refactor: Remove strncpy/STRNCPY. (#6008)

Closes #731
References #851

Note: This does not remove some intentional legacy usages of strncpy.
      - memcpy isn't equivalent because it doesn't check the string
        length of `src`, and doesn't zero-out the remainder of `dst`.
      - xstrlcpy isn't equivalent because it doesn't zero-out the
        remainder of `dst`. Some Vim logic depends on that (e.g.
        ex_append which calls vim_strnsave).

Helped-by: Douglas Schneider <ds3@ualberta.ca>
Helped-by: oni-link <knil.ino@gmail.com>
Helped-by: James McCoy <jamessan@jamessan.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index dcd32acfb7..d964da371a 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -1608,7 +1608,7 @@ static void foldAddMarker(linenr_T lnum, char_u *marker, size_t markerlen)
       STRLCPY(newline + line_len, marker, markerlen + 1);
     else {
       STRCPY(newline + line_len, cms);
-      STRNCPY(newline + line_len + (p - cms), marker, markerlen);
+      memcpy(newline + line_len + (p - cms), marker, markerlen);
       STRCPY(newline + line_len + (p - cms) + markerlen, p + 2);
     }
 
@@ -1673,7 +1673,8 @@ static void foldDelMarker(linenr_T lnum, char_u *marker, size_t markerlen)
     if (u_save(lnum - 1, lnum + 1) == OK) {
       /* Make new line: text-before-marker + text-after-marker */
       newline = xmalloc(STRLEN(line) - len + 1);
-      STRNCPY(newline, line, p - line);
+      assert(p >= line);
+      memcpy(newline, line, (size_t)(p - line));
       STRCPY(newline + (p - line), p + len);
       ml_replace(lnum, newline, FALSE);
     }