Add use of Windows Wide CRT API for env. vars (#20084)

* Add use of Windows Wide CRT API for env. vars

Replaces use of CRT API `getenv` and `putenv` with respectively
`_wgetenv` and `_wputenv`. Motivation is to reliably convert environment
variables to UTF-8, and the wide API is best there, because it's
reliably UTF-16.

Changed the hack in `lib/std/private/win_setenv.nim` by switching the
order of the Unicode and MBCS environment update; Unicode first, MBCS
second. Because `_wgetenv`/`_wputenv` is now used, the Unicode
environment will be initialized, so it should always be updated.

Stop updating MBCS environment with the name of `getEnv`. It's not
necessarily true that MBCS encoding and the `string` encoding is the
same. Instead convert UTF-16 to current Windows code page with
`wcstombs`, and use that string to update MBCS.

Fixes regression in `6b3c77e` that caused `std/envvars.getEnv` or
`std/os.getEnv` on Windows to return non-UTF-8 encoded strings.

Add tests that test environment variables with Unicode characters in
their name or value.

* Fix test issues

Fixes

* `nim cpp` didn't compile the tests
* Nimscript import of `tosenv.nim` from `test_nimscript.nims` failed
  with "cannot importc"

* Fix missing error check on `wcstombs`

* Fix ANSI testing errors

* Separate ANSI-related testing to their own tests, and only executing
  them if running process has a specific code page
  * Setting locale with `setlocale` was not reliable and didn't work on
    certain machines
* Add handling of a "no character representation" error in second
  `wcstombs` call

* tests/newruntime_misc: Increment allocCount

Increments overall allocations in `tnewruntime_misc` test. This is
because `getEnv` now does an additional allocation: allocation of the
UTF-16 string used as parameter to `c_wgetenv`.

* Revert "tests/newruntime_misc: Increment allocCount"

This reverts commit 4d4fe8bd3edb1bfc6d600f247af797c7552f5477.

* tests/newruntime_misc: Increment allocCount on Windows

Increments overall allocations in `tnewruntime_misc` test for Windows.
This is because `getEnv` on Windows now does an additional allocation:
allocation of the UTF-16 string used as parameter to `c_wgetenv`.

* Refactor, adding suggestions from code review

Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>

* Document, adding suggestions

Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>

Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>
Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/tests/destructor/tnewruntime_misc.nim b/tests/destructor/tnewruntime_misc.nim
index ac061f2f7..21c70557d 100644
--- a/tests/destructor/tnewruntime_misc.nim
+++ b/tests/destructor/tnewruntime_misc.nim
@@ -137,7 +137,16 @@ proc xx(xml: string): MyObject =
 
 
 discard xx("test")
-echo getAllocStats() - s1
+
+# Windows has 1 extra allocation in `getEnv` - there it allocates parameter to
+# `_wgetenv` (WideCString). Therefore subtract by 1 to match other OSes'
+# allocation.
+when defined(windows):
+  import std/importutils
+  privateAccess(AllocStats)
+  echo getAllocStats() - s1 - AllocStats(allocCount: 1, deallocCount: 1)
+else:
+  echo getAllocStats() - s1
 
 # bug #13457
 var s = "abcde"