vim-patch:8.2.4734: getcharpos() may change a mark position (#18077)

Problem:    getcharpos() may change a mark position.
Solution:   Copy the mark position. (closes vim/vim#10148)
https://github.com/vim/vim/commit/3caf1cce2b85a8f24195d057f0ad63082543e99e

2 files changed, 22 insertions, 19 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index c1905b31d0..3e855ece15 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -7739,7 +7739,6 @@ pos_T *var2fpos(const typval_T *const tv, const bool dollar_lnum, int *const ret
   FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
 {
   static pos_T pos;
-  pos_T *pp;
 
   // Argument can be [lnum, col, coladd].
   if (tv->v_type == VAR_LIST) {
@@ -7799,33 +7798,31 @@ pos_T *var2fpos(const typval_T *const tv, const bool dollar_lnum, int *const ret
   if (name == NULL) {
     return NULL;
   }
-  if (name[0] == '.') {  // Cursor.
+
+  pos.lnum = 0;
+  if (name[0] == '.') {
+    // cursor
     pos = curwin->w_cursor;
-    if (charcol) {
-      pos.col = buf_byteidx_to_charidx(curbuf, pos.lnum, pos.col);
-    }
-    return &pos;
-  }
-  if (name[0] == 'v' && name[1] == NUL) {  // Visual start.
+  } else if (name[0] == 'v' && name[1] == NUL) {
+    // Visual start
     if (VIsual_active) {
       pos = VIsual;
     } else {
       pos = curwin->w_cursor;
     }
-    if (charcol) {
-      pos.col = buf_byteidx_to_charidx(curbuf, pos.lnum, pos.col);
-    }
-    return &pos;
-  }
-  if (name[0] == '\'') {  // Mark.
-    pp = getmark_buf_fnum(curbuf, (uint8_t)name[1], false, ret_fnum);
+  } else if (name[0] == '\'') {
+    // mark
+    const pos_T *const pp = getmark_buf_fnum(curbuf, (uint8_t)name[1], false, ret_fnum);
     if (pp == NULL || pp == (pos_T *)-1 || pp->lnum <= 0) {
       return NULL;
     }
+    pos = *pp;
+  }
+  if (pos.lnum != 0) {
     if (charcol) {
-      pp->col = buf_byteidx_to_charidx(curbuf, pp->lnum, pp->col);
+      pos.col = buf_byteidx_to_charidx(curbuf, pos.lnum, pos.col);
     }
-    return pp;
+    return &pos;
   }
 
   pos.coladd = 0;
diff --git a/src/nvim/testdir/test_cursor_func.vim b/src/nvim/testdir/test_cursor_func.vim
index 57825b4551..9ba82e3b70 100644
--- a/src/nvim/testdir/test_cursor_func.vim
+++ b/src/nvim/testdir/test_cursor_func.vim
@@ -140,12 +140,12 @@ func Test_getcharpos()
   call assert_fails('call getcharpos({})', 'E731:')
   call assert_equal([0, 0, 0, 0], getcharpos(0))
   new
-  call setline(1, ['', "01\tà4è678", 'Ⅵ', '012345678'])
+  call setline(1, ['', "01\tà4è678", 'Ⅵ', '012345678', ' │  x'])
 
   " Test for '.' and '$'
   normal 1G
   call assert_equal([0, 1, 1, 0], getcharpos('.'))
-  call assert_equal([0, 4, 1, 0], getcharpos('$'))
+  call assert_equal([0, 5, 1, 0], getcharpos('$'))
   normal 2G6l
   call assert_equal([0, 2, 7, 0], getcharpos('.'))
   normal 3G$
@@ -159,6 +159,12 @@ func Test_getcharpos()
   delmarks m
   call assert_equal([0, 0, 0, 0], getcharpos("'m"))
 
+  " Check mark does not move
+  normal 5Gfxma
+  call assert_equal([0, 5, 5, 0], getcharpos("'a"))
+  call assert_equal([0, 5, 5, 0], getcharpos("'a"))
+  call assert_equal([0, 5, 5, 0], getcharpos("'a"))
+
   " Test for the visual start column
   vnoremap <expr> <F3> SaveVisualStartCharPos()
   let g:VisualStartPos = []