Make `<string_view>` slimmer by default by frederick-vs-ja · Pull Request #4633

Make `<string_view>` slimmer by default by frederick-vs-ja · Pull Request #4633 · microsoft/STL

The new header `<__msvc_string_view.hpp>` provides `char_traits` and
`basic_string_view` and related utilities. `<string_view>` shouldn't
provide other utilities in `<xstring>`.

`<ranges>` seemingly still need to include `<xmemory>` in C++23
due to `elements_of` whose default template argument depends on
`allocator`.

Escape hatch `_LEGACY_CODE_ASSUMES_STRING_VIEW_INCLUDES_XSTRING` is
added to restore legacy inclusion.

MSVC-internal changes are needed due to the new internal header.

This was referenced

Jun 6, 2024

kou pushed a commit to apache/arrow that referenced this pull request

Jun 7, 2024

### Rationale for this change

I work on MSVC's STL, and we regularly build popular open-source projects, including yours, with development builds of the MSVC toolset. This allows us to find and fix toolset regressions before they affect users, and also allows us to provide advance notice of breaking changes, which is the case here.

We recently merged microsoft/STL#4633 which will ship in VS 2022 17.11 Preview 3. This improved build throughput by refactoring `<string_view>` so that it no longer drags in `std::string`. It's also a source-breaking change for code that wasn't properly including `<string>`. Your `cpp/src/arrow/json/object_writer.h` declares `std::string Serialize();` without including `<string>`. When built with our updated STL, this will emit a compiler error:

```
C:\gitP\apache\arrow\cpp\src\arrow/json/object_writer.h(39): error C2039: 'string': is not a member of 'std'
```

### What changes are included in this PR?

The fix is simple and portable: include the necessary header.

### Are these changes tested?

Nope, I'm totally YOLOing it. If it builds, it's good.

(This will be tested in MSVC's internal "Real World Code" test infrastructure. Also, after VS 2022 17.11 ships, your existing build/test coverage will ensure that this keeps compiling.)

### Are there any user-facing changes?

No.

Authored-by: Stephan T. Lavavej <stl@microsoft.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

This was referenced

Jun 7, 2024

BillyONeal pushed a commit to microsoft/vcpkg that referenced this pull request

Jun 10, 2024

…member of 'std' (#39160)

In an internal version of Visual Studio, `arrow`, `concurrencpp` and
`qtwebengine` install failed with following error:
```
arrow:        \cpp\src\arrow/json/object_writer.h(39): error C2039: 'string': is not a member of 'std'
concurrencpp: \include\concurrencpp/threads/thread.h(23): error C2039: 'string': is not a member of 'std'
qtwebengine:  \src\3rdparty\gn\src\gn\escape.h(77): error C2039: 'string': is not a member of 'std'
```
This issue caused by the STL PR:
microsoft/STL#4633, and according to Stephan's
suggestion, the affected files need to include the `Standard <string>
header`.

I have submitted an issue on the qt upstream:
https://bugreports.qt.io/browse/QTBUG-126156

This was referenced

Jul 31, 2024