[libc++] [test] Fix portability issues for MSVC (#93259)

* Guard `std::__make_from_tuple_impl` tests with `#ifdef _LIBCPP_VERSION` and `LIBCPP_STATIC_ASSERT`.
* Change `_LIBCPP_CONSTEXPR_SINCE_CXX20` to `TEST_CONSTEXPR_CXX20`.
+ Other functions in `variant.swap/swap.pass.cpp` were already using the proper test macro.
* Mark `what` as `[[maybe_unused]]` when used by `TEST_LIBCPP_REQUIRE`.
  + This updates one occurrence in `libcxx/test/libcxx` for consistency.
* Windows `_putenv_s()` takes 2 arguments, not 3.
  + See MSVC documentation: https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/putenv-s-wputenv-s?view=msvc-170
+ POSIX `setenv()` takes `int overwrite`, but Windows `_putenv_s()` always overwrites.
* Avoid non-Standard zero-length arrays.
  + Followup to #74183 and #79792.
* Add `operator++()` to `unsized_it`.
+ The Standard requires this due to [N4981][] [move.iter.requirements]/1 "The template parameter `Iterator` shall
  either meet the *Cpp17InputIterator* requirements ([input.iterators])
  or model `input_iterator` ([iterator.concept.input])."
+ MSVC's STL requires this because it has a strengthened exception
  specification in `move_iterator` that inspects the underlying iterator's
  increment operator.
* `uniform_int_distribution` forbids `int8_t`/`uint8_t`.
  + See [N4981][] [rand.req.genl]/1.5. MSVC's STL enforces this.
+ Note that when changing the distribution's `IntType`, we need to be
  careful to preserve the original value range of `[0, max_input]`.
* fstreams are constructible from `const fs::path::value_type*` on wide systems.
  + See [ifstream.cons], [ofstream.cons], [fstream.cons].
* In `msvc_stdlib_force_include.h`, map `_HAS_CXX23` to `TEST_STD_VER` 23 instead of 99.
+ On 2023-05-23, 7140050
  started recognizing 23 as a distinct value.
* Fix test name typo: `destory_elements.pass.cpp` => `destroy_elements.pass.cpp`

[N4981]: https://wg21.link/N4981

Author: StephanTLavavej

libcxx/test/libcxx/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp

@@ -73,7 +73,7 @@ L link link_to_link
   TEST_VALIDATE_EXCEPTION(
       std::runtime_error,
       [&]([[maybe_unused]] const std::runtime_error& e) {
-        std::string_view what{"tzdb: requested time zone not found"};
+        [[maybe_unused]] std::string_view what{"tzdb: requested time zone not found"};
         TEST_LIBCPP_REQUIRE(
             e.what() == what,
             TEST_WRITE_CONCATENATED("\nExpected exception ", what, "\nActual exception   ", e.what(), '\n'));

libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains_subrange.pass.cpp

@@ -24,6 +24,7 @@
 //                                              Proj1 proj1 = {}, Proj2 proj2 = {});                 // since C++23
 
 #include <algorithm>
+#include <array>
 #include <cassert>
 #include <concepts>
 #include <ranges>
@@ -130,10 +131,10 @@ constexpr void test_iterators() {
   }
 
   { // range has zero length
-    int a[]       = {};
-    int p[]       = {3, 4, 2};
-    auto whole    = std::ranges::subrange(Iter1(a), Sent1(Iter1(a)));
-    auto subrange = std::ranges::subrange(Iter2(p), Sent2(Iter2(std::end(p))));
+    std::array<int, 0> a = {};
+    int p[]              = {3, 4, 2};
+    auto whole           = std::ranges::subrange(Iter1(a.data()), Sent1(Iter1(a.data())));
+    auto subrange        = std::ranges::subrange(Iter2(p), Sent2(Iter2(std::end(p))));
     {
       bool ret = std::ranges::contains_subrange(whole.begin(), whole.end(), subrange.begin(), subrange.end());
       assert(!ret);
@@ -145,10 +146,10 @@ constexpr void test_iterators() {
   }
 
   { // subrange has zero length
-    int a[]       = {3, 4, 2};
-    int p[]       = {};
-    auto whole    = std::ranges::subrange(Iter1(a), Sent1(Iter1(std::end(a))));
-    auto subrange = std::ranges::subrange(Iter2(p), Sent2(Iter2(p)));
+    int a[]              = {3, 4, 2};
+    std::array<int, 0> p = {};
+    auto whole           = std::ranges::subrange(Iter1(a), Sent1(Iter1(std::end(a))));
+    auto subrange        = std::ranges::subrange(Iter2(p.data()), Sent2(Iter2(p.data())));
     {
       bool ret = std::ranges::contains_subrange(whole.begin(), whole.end(), subrange.begin(), subrange.end());
       assert(ret);
@@ -160,10 +161,10 @@ constexpr void test_iterators() {
   }
 
   { // range and subrange both have zero length
-    int a[]       = {};
-    int p[]       = {};
-    auto whole    = std::ranges::subrange(Iter1(a), Sent1(Iter1(a)));
-    auto subrange = std::ranges::subrange(Iter2(p), Sent2(Iter2(p)));
+    std::array<int, 0> a = {};
+    std::array<int, 0> p = {};
+    auto whole           = std::ranges::subrange(Iter1(a.data()), Sent1(Iter1(a.data())));
+    auto subrange        = std::ranges::subrange(Iter2(p.data()), Sent2(Iter2(p.data())));
     {
       bool ret = std::ranges::contains_subrange(whole.begin(), whole.end(), subrange.begin(), subrange.end());
       assert(ret);

libcxx/test/std/containers/sequences/vector/vector.modifiers/destory_elements.pass.cpp renamed to libcxx/test/std/containers/sequences/vector/vector.modifiers/destroy_elements.pass.cpp

@@ -37,7 +37,7 @@ constexpr bool test_non_convert_to_path() {
   static_assert(!std::is_constructible_v<std::fstream, const std::basic_string_view<CharT>>);
 
   // Char* pointers
-  if constexpr (!std::is_same_v<CharT, char>)
+  if constexpr (!std::is_same_v<CharT, char> && !std::is_same_v<CharT, fs::path::value_type>)
     static_assert(!std::is_constructible_v<std::fstream, const CharT*>);
 
   // Iterators

libcxx/test/std/input.output/file.streams/fstreams/fstream.cons/path.pass.cpp

@@ -38,7 +38,7 @@ constexpr bool test_non_convert_to_path() {
   static_assert(!std::is_constructible_v<std::ifstream, const std::basic_string_view<CharT>>);
 
   // Char* pointers
-  if constexpr (!std::is_same_v<CharT, char>)
+  if constexpr (!std::is_same_v<CharT, char> && !std::is_same_v<CharT, fs::path::value_type>)
     static_assert(!std::is_constructible_v<std::ifstream, const CharT*>);
 
   // Iterators

libcxx/test/std/input.output/file.streams/fstreams/ifstream.cons/path.pass.cpp

@@ -37,7 +37,7 @@ constexpr bool test_non_convert_to_path() {
   static_assert(!std::is_constructible_v<std::ofstream, const std::basic_string_view<CharT>>);
 
   // Char* pointers
-  if constexpr (!std::is_same_v<CharT, char>)
+  if constexpr (!std::is_same_v<CharT, char> && !std::is_same_v<CharT, fs::path::value_type>)
     static_assert(!std::is_constructible_v<std::ofstream, const CharT*>);
 
   // Iterators

libcxx/test/std/input.output/file.streams/fstreams/ofstream.cons/path.pass.cpp

@@ -21,6 +21,7 @@ struct unsized_it {
   using difference_type = std::ptrdiff_t;
 
   value_type& operator*() const;
+  unsized_it& operator++();
   bool operator==(const unsized_it&) const;
   difference_type operator-(const unsized_it&) const { return 0; }
 };

libcxx/test/std/iterators/predef.iterators/move.iterators/sized_sentinel.compile.pass.cpp

@@ -17,6 +17,7 @@
 #include <cassert>
 #include <climits>
 #include <cstdint>
+#include <limits>
 #include <random>
 #include <type_traits>
 
@@ -69,12 +70,14 @@ T basic_gcd(T m, T n) {
 template <typename Input>
 void do_fuzzy_tests() {
   std::mt19937 gen(1938);
-  std::uniform_int_distribution<Input> distrib;
+  using DistIntType         = std::conditional_t<sizeof(Input) == 1, int, Input>; // See N4981 [rand.req.genl]/1.5
+  constexpr Input max_input = std::numeric_limits<Input>::max();
+  std::uniform_int_distribution<DistIntType> distrib(0, max_input);
 
   constexpr int nb_rounds = 10000;
   for (int i = 0; i < nb_rounds; ++i) {
-    Input n = distrib(gen);
-    Input m = distrib(gen);
+    Input n = static_cast<Input>(distrib(gen));
+    Input m = static_cast<Input>(distrib(gen));
     assert(std::gcd(n, m) == basic_gcd(n, m));
   }
 }

libcxx/test/std/numerics/numeric.ops/numeric.ops.gcd/gcd.pass.cpp

@@ -32,7 +32,7 @@ static void set_tz(std::string zone) {
   // Unlike POSIX it does not mention the string of putenv becomes part
   // of the environment.
 
-  int status = _putenv_s("TZ", zone.c_str(), 1);
+  int status = _putenv_s("TZ", zone.c_str());
   assert(status == 0);
 }
 

libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/current_zone.pass.cpp

@@ -40,7 +40,7 @@ static void test_exception([[maybe_unused]] std::string_view zone) {
   TEST_VALIDATE_EXCEPTION(
       std::runtime_error,
       [&]([[maybe_unused]] const std::runtime_error& e) {
-        std::string_view what{"tzdb: requested time zone not found"};
+        [[maybe_unused]] std::string_view what{"tzdb: requested time zone not found"};
         TEST_LIBCPP_REQUIRE(
             e.what() == what,
             TEST_WRITE_CONCATENATED("\nExpected exception ", what, "\nActual exception   ", e.what(), '\n'));