vim-patch:8.2.3601: check for overflow in put count does not work well

Problem:    Check for overflow in put count does not work well.
Solution:   Improve the overflow check. (Ozaki Kiichi, closes vim/vim#9102)
fa53722367

Add some casts as Nvim uses size_t variables in some places.

We could technically adjust the logic to check for overflow outside of size_t's
range, but it's much easier to just port the patch exactly (also means we can
use the same tests).

v:sizeoflong is N/A, so convert the 64-bit tests to Lua and use the FFI to check
long's size.

test/functional/legacy/put_spec.lua

@@ -0,0 +1,45 @@
+local helpers = require('test.functional.helpers')(after_each)
+local clear = helpers.clear
+local exec_lua = helpers.exec_lua
+local meths = helpers.meths
+local source = helpers.source
+local eq = helpers.eq
+
+local function sizeoflong()
+  if not exec_lua('return pcall(require, "ffi")') then
+    pending('missing LuaJIT FFI')
+  end
+  return exec_lua('return require("ffi").sizeof(require("ffi").typeof("long"))')
+end
+
+describe('put', function()
+  before_each(clear)
+  after_each(function() eq({}, meths.get_vvar('errors')) end)
+
+  it('very large count 64-bit', function()
+    if sizeoflong() < 8 then
+      pending('Skipped: only works with 64 bit long ints')
+    end
+
+    source [[
+      new
+      let @" = 'x'
+      call assert_fails('norm 44444444444444p', 'E1240:')
+      bwipe!
+    ]]
+  end)
+
+  it('very large count (visual block) 64-bit', function()
+    if sizeoflong() < 8 then
+      pending('Skipped: only works with 64 bit long ints')
+    end
+
+    source [[
+      new
+      call setline(1, 'x')
+      exe "norm \<C-V>y"
+      call assert_fails('norm 44444444444444p', 'E1240:')
+      bwipe!
+    ]]
+  end)
+end)