vim-patch:8.2.3492: crash when pasting too many times

Problem:    Crash when pasting too many times.
Solution:   Limit the size to what fits in an int. (closes vim/vim#8962)
eeed1c7ae0

Note that this overflow check pretty bad.
It also doesn't work well on Windows (where sizeof(int) == sizeof(long)).
This is all temporary; everything here is rewritten in future patches anyway.

e_resulting_text_too_long was already cherry-picked.

totlen is size_t in Nvim, but is int in Vim. This means we'll need some casts.

We could technically adjust the logic in do_put to use the entire range of
size_t in stuff like totlen, but there's not much gain, and it's much easier to
just port the patch like Vim as was done before (also allows us to use the same
tests).

src/nvim/ops.c

@@ -3431,8 +3431,13 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
       }
 
       do {
-        totlen = (size_t)(count * yanklen);
-        if (totlen > 0) {
+        const long multlen = count * yanklen;
+
+        totlen = (size_t)(int)multlen;
+        if (totlen != (size_t)multlen) {
+          emsg(_(e_resulting_text_too_long));
+          break;
+        } else if (totlen > 0) {
           oldp = ml_get(lnum);
           if (lnum > start_lnum) {
             pos_T pos = {

src/nvim/testdir/test_put.vim

@@ -138,6 +138,13 @@ func Test_p_with_count_leaves_mark_at_end()
   bwipe!
 endfunc
 
+func Test_very_larg_count()
+  new
+  let @" = 'x'
+  call assert_fails('norm 44444444444444p', 'E1240:')
+  bwipe!
+endfunc
+
 func Test_put_above_first_line()
   new
   let @" = 'text'