# HG changeset patch
# User Christian Brabandt <cb@256bit.org>
# Date 1696613407 -7200
# Node ID 0081ca43bee9dae8b3b8b70ddc981b31e111ffc4
# Parent  0864a58c7a4ac4bd16f3adbb1e1603fe808cef48
patch 9.0.1995: Invalid memory access with empty 'foldexpr'

Commit: https://github.com/vim/vim/commit/a991ce9c083bb8c02b1b1ec34ed35728197050f3
Author: zeertzjq <zeertzjq@outlook.com>
Date:   Fri Oct 6 19:16:36 2023 +0200

    patch 9.0.1995: Invalid memory access with empty 'foldexpr'

    Problem:  Invalid memory access when 'foldexpr' returns empty string.
    Solution: Check for NUL.

    closes: #13293

    Signed-off-by: Christian Brabandt <cb@256bit.org>
    Co-authored-by: zeertzjq <zeertzjq@outlook.com>

diff --git a/src/eval.c b/src/eval.c
--- a/src/eval.c
+++ b/src/eval.c
@@ -968,7 +968,7 @@ eval_foldexpr(win_T *wp, int *cp)
 	    // If the result is a string, check if there is a non-digit before
 	    // the number.
 	    s = tv.vval.v_string;
-	    if (!VIM_ISDIGIT(*s) && *s != '-')
+	    if (*s != NUL && !VIM_ISDIGIT(*s) && *s != '-')
 		*cp = *s++;
 	    retval = atol((char *)s);
 	}
diff --git a/src/testdir/test_fold.vim b/src/testdir/test_fold.vim
--- a/src/testdir/test_fold.vim
+++ b/src/testdir/test_fold.vim
@@ -1769,4 +1769,13 @@ func Test_foldcolumn_linebreak_control_c
   bwipe!
 endfunc
 
+" This used to cause invalid memory access
+func Test_foldexpr_return_empty_string()
+  new
+  setlocal foldexpr='' foldmethod=expr
+  redraw
+
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1995,
+/**/
     1994,
 /**/
     1993,