[libc++][test] Make some string tests MSVC-friendly

[CaseyCarter]

Summary

• Using one-or-two letter names for globals is asking for shadowing warnings.
• MSVCSTL's container proxy allocations strike again
• MSVCSTL's <string> doesn't define std::out_of_range
• basic_string::substr takes two arguments of type size_type. Let's use that type instead of size_t and ptrdiff_t to avoid narrowing warnings.

[philnik]

LGTM % nit.

libcxx/test/std/strings/basic.string/string.cons/dtor.pass.cpp

48–50

Is this change just academic, or is MSVC actually allocating more than once?

libcxx/test/std/strings/basic.string/string.ops/string_substr/substr_rvalue.pass.cpp

31

Nit: the formatting looks wrong.

[ldionne]

LGTM, the CI issues look unrelated. I just came back from OOO so I guess this might have been fixed already.

[philnik]

In D141253#4036393, @ldionne wrote:

LGTM, the CI issues look unrelated. I just came back from OOO so I guess this might have been fixed already.

It's not fixed yet, but it's unrelated. Sorry for breaking the CI.

[CaseyCarter]

libcxx/test/std/strings/basic.string/string.cons/dtor.pass.cpp

48–50

This is yet another manifestation of MSVCSTL containers' additional memory allocation when iterator debugging is active.

libcxx/test/std/strings/basic.string/string.ops/string_substr/substr_rvalue.pass.cpp

31

I made these quite long and figured I'd wrap them since nothing in the file was much over 80. I should have simply clang-formatted, which I'll do now.

libcxx/test/std/strings/basic.string/string.cons/dtor.pass.cpp

struct throwing_alloc
     typedef T value_type;
     throwing_alloc(const throwing_alloc&);
     T *allocate(size_t);
     ~throwing_alloc() noexcept(false);
 };
 
 // Test that it's possible to take the address of basic_string's destructors
 // by creating globals which will register their destructors with cxa_atexit.
-std::string s;
+std::string unused_string;
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
-std::wstring ws;
+std::wstring unused_wide_string;
 #endif
 
 static_assert(std::is_nothrow_destructible<std::string>::value, "");
 static_assert(std::is_nothrow_destructible<
                 std::basic_string<char, std::char_traits<char>, test_allocator<char>>>::value, "");
 LIBCPP_STATIC_ASSERT(!std::is_nothrow_destructible<
                      std::basic_string<char, std::char_traits<char>, throwing_alloc<char>>>::value, "");
 
 TEST_CONSTEXPR_CXX20 bool test() {
   test_allocator_statistics alloc_stats;
   {
     std::basic_string<char, std::char_traits<char>, test_allocator<char>> str2((test_allocator<char>(&alloc_stats)));
     str2 = "long long string so no SSO";
-    assert(alloc_stats.alloc_count == 1);
+    assert(alloc_stats.alloc_count > 0);
+    LIBCPP_ASSERT(alloc_stats.alloc_count == 1);
   }
   assert(alloc_stats.alloc_count == 0);
 
   return true;
 }
 
 int main(int, char**)
 {
   test();
 #if TEST_STD_VER > 17
   static_assert(test());
 #endif
 
   return 0;
 }

libcxx/test/std/strings/basic.string/string.ops/string_substr/substr_rvalue.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
 
 // <string>
 
 // constexpr basic_string substr(size_type pos = 0, size_type n = npos) &&;
 
 #include <algorithm>
+#include <stdexcept>
 #include <string>
 
 #include "constexpr_char_traits.h"
 #include "make_string.h"
 #include "min_allocator.h"
 #include "test_allocator.h"
 
 #define STR(string) MAKE_CSTRING(typename S::value_type, string)
 
 constexpr struct should_throw_exception_t {
 } should_throw_exception;
 
 template <class S>
-constexpr void test(S orig, size_t pos, ptrdiff_t n, S expected) {
+constexpr void test(S orig, typename S::size_type pos, typename S::size_type n, const S expected) {
   S str = std::move(orig).substr(pos, n);
   LIBCPP_ASSERT(orig.__invariants());
   LIBCPP_ASSERT(str.__invariants());
   assert(str == expected);
 }
 
 template <class S>
-constexpr void test(S orig, size_t pos, ptrdiff_t n, should_throw_exception_t) {
+constexpr void test(S orig, typename S::size_type pos, typename S::size_type n, should_throw_exception_t) {
 #ifndef TEST_HAS_NO_EXCEPTIONS
   if (!std::is_constant_evaluated()) {
     try {
       S str = std::move(orig).substr(pos, n);
       assert(false);
     } catch (const std::out_of_range&) {
     }
   }