Repo sync for protected branch

docs/c-language/c-keywords.md

@@ -47,6 +47,8 @@ The C language uses the following keywords:
         **`struct`**\
         **`switch`**\
         **`typedef`**\
+        **[`typeof`](typeof-c.md)**\
+        **[`typeof_unqual`](typeof-unqual-c.md)**\
         **`union`**\
         **`unsigned`**\
         **`void`**\
@@ -67,12 +69,9 @@ The C language uses the following keywords:
     :::column-end:::
 :::row-end:::
 
-<sup>1</sup>  Keywords introduced in ISO C99.
-
-<sup>2</sup>   Keywords introduced in ISO C11.
-
-<sup>a</sup>  Starting in Visual Studio 2019 version 16.8, these keywords are supported in code compiled as C when the **`/std:c11`** or **`/std:c17`** compiler options are specified.
-
+<sup>1</sup>  Keywords introduced in ISO C99.\
+<sup>2</sup>   Keywords introduced in ISO C11.\
+<sup>a</sup>  Starting in Visual Studio 2019 version 16.8, these keywords are supported in code compiled as C when the **`/std:c11`** or **`/std:c17`** compiler options are specified.\
 <sup>b</sup>  Starting in Visual Studio 2019 version 16.8, these keywords are recognized but not supported by the compiler in code compiled as C when the **`/std:c11`** or **`/std:c17`** compiler options are specified.
 
 You can't redefine keywords. However, you can specify text to replace keywords before compilation by using C [preprocessor directives](../preprocessor/preprocessor-directives.md).
@@ -105,6 +104,8 @@ The following keywords and special identifiers are recognized by the Microsoft C
     :::column:::
         **`__stdcall`**<sup>5</sup>\
         **`__try`**<sup>5</sup>\
+        **[`__typeof__`](typeof-c.md)**\
+        **[`__typeof_unqual__`](typeof-unqual-c.md)**\
         **`dllexport`**<sup>4</sup>\
         **`dllimport`**<sup>4</sup>\
         **`naked`**<sup>4</sup>\
@@ -113,17 +114,14 @@ The following keywords and special identifiers are recognized by the Microsoft C
     :::column-end:::
 :::row-end:::
 
-<sup>3</sup> The **`__based`** keyword has limited uses for 32-bit and 64-bit target compilations.
-
-<sup>4</sup> These are special identifiers when used with **`__declspec`**; their use in other contexts is unrestricted.
-
-<sup>5</sup> For compatibility with previous versions, these keywords are available both with two leading underscores and a single leading underscore when Microsoft extensions are enabled.
-
+<sup>3</sup> The **`__based`** keyword has limited uses for 32-bit and 64-bit target compilations.\
+<sup>4</sup> These are special identifiers when used with **`__declspec`**; their use in other contexts is unrestricted.\
+<sup>5</sup> For compatibility with previous versions, these keywords are available both with two leading underscores and a single leading underscore when Microsoft extensions are enabled.\
 <sup>6</sup> If you don't include <assert.h>, the Microsoft Visual C compiler maps **`static_assert`** to the C11 **`_Static_assert`** keyword.
 
-Microsoft extensions are enabled by default. To assist in creating portable code, you can disable Microsoft extensions by specifying the [/Za \(Disable language extensions)](../build/reference/za-ze-disable-language-extensions.md) option during compilation. When you use this option, some Microsoft-specific keywords are disabled.
+Microsoft extensions are enabled by default. To help create portable code, you can disable Microsoft extensions by specifying the [/Za \(Disable language extensions)](../build/reference/za-ze-disable-language-extensions.md) option during compilation. When you use this option, some Microsoft-specific keywords are disabled.
 
-When Microsoft extensions are enabled, you can use the keywords listed above in your programs. To conform to the language standard, most of these keywords are prefaced by a double underscore. The four exceptions, **`dllexport`**, **`dllimport`**, **`naked`**, and **`thread`**, are used only with **`__declspec`** and don't require a leading double underscore. For backward compatibility, single-underscore versions of the rest of the keywords are supported.
+When Microsoft extensions are enabled, you can use the keywords listed above in your programs. To conform to the language standard, most of these keywords have a leading double underscore. The four exceptions, **`dllexport`**, **`dllimport`**, **`naked`**, and **`thread`**, are used only with **`__declspec`** and don't require a leading double underscore. For backward compatibility, single-underscore versions of the rest of the keywords are supported.
 
 ## See also
 

docs/c-language/c-type-specifiers.md

@@ -3,7 +3,6 @@ description: "Learn more about: C Type Specifiers"
 title: "C Type Specifiers"
 ms.date: "01/29/2018"
 helpviewer_keywords: ["type specifiers, C", "specifiers, type"]
-ms.assetid: fbe13441-04c3-4829-b047-06d374adc2b6
 ---
 # C Type Specifiers
 
@@ -70,4 +69,6 @@ You can create more type specifiers with **`typedef`** declarations, as describe
 
 ## See also
 
-[Declarations and Types](../c-language/declarations-and-types.md)
+[Declarations and Types](../c-language/declarations-and-types.md)\
+[`typeof, __typeof__` (C23)](typeof-c.md)\
+[`typeof_unqual, __typeof_unqual__` (C23)](typeof-unqual-c.md)

docs/c-language/toc.yml

@@ -171,6 +171,10 @@ items:
             href: ../c-language/c-type-specifiers.md
           - name: Data type specifiers and equivalents
             href: ../c-language/data-type-specifiers-and-equivalents.md
+          - name: typeof
+            href: typeof-c.md
+          - name: typeof_unqual
+            href: typeof-unqual-c.md
       - name: Type qualifiers
         href: ../c-language/type-qualifiers.md
       - name: Declarators and variable declarations

docs/c-language/typeof-c.md

@@ -0,0 +1,59 @@
+---
+title: "typeof, __typeof__ (C23)"
+description: "Describes Microsoft Visual C23 typeof operator"
+ms.date: 02/06/2024
+helpviewer_keywords: ["typeof keyword [C]", "__typeof__ keyword [C]"]
+---
+# `typeof`, `__typeof__` (C23)
+
+New in the C23 standard, the **`typeof`** operator is a unary operator that returns the type of an expression. It can be used in type declarations, type casts, type checks, and so on. It gets the type of a variable, function, or any C expression.
+
+The **`__typeof__`** keyword is a Microsoft-specific extension that provides the same functionality as **`typeof`**. The `__typeof__` keyword differs from `typeof` only in that it's available when compiling for all versions of C (not just `/std:clatest`), and it may ease porting code between other compilers that support `__typeof__`.
+
+### `typeof` syntax
+
+```c
+typeof(type)
+typeof(constant-expression)
+__typeof__(constant-expression)
+```
+
+### `typeof` example
+
+This example uses `typeof()`, but the behavior is the same if you use `__typeof__`.
+
+```c
+// Compile with /std:clatest
+
+#include <stdio.h>
+
+double func()
+{
+    3.14;
+}
+
+#define POINTER(T) typeof(T*)
+
+int main()
+{
+    auto a = func(); // the type for a (double) is inferred, but requires initialization at point of declaration
+    typeof(func()) b; // the type for b is double, but didn't have to be initialized at point of declaration
+
+    // Some declarations using typeof
+    POINTER(int) p1 = NULL; // p1 is int*
+
+    typeof(double(void))* pFunc = func; // pFunc is a pointer to a function that takes no arguments and returns a double
+    printf("pFunc() returns %f\n", pFunc());
+
+    return 0;
+}
+```
+
+## Requirements
+
+Requires Visual Studio 17.9 or later, or `cl.exe` version 19.39.33428 or later.
+To use `typeof`, compile with [`/std:clatest`](../build/reference/std-specify-language-standard-version.md).
+
+## See also
+
+[`/std` (Specify Language Standard Version)](../build/reference/std-specify-language-standard-version.md)\

docs/c-language/typeof-unqual-c.md

@@ -0,0 +1,57 @@
+---
+title: "typeof_unqual, __typeof_unqual__ (C23)"
+description: "Describes Microsoft Visual C23 typeof_unqual operator"
+ms.date: 02/06/2024
+helpviewer_keywords: ["typeof_unqual keyword [C]", "__typeof_unqual__ keyword [C]"]
+---
+# `typeof_unqual`, `__typeof_unqual__` (C23)
+
+New in the C23 standard, the **`typeof_unqual`** operator is a unary operator that returns the type of an expression after discarding qualifiers such as `const`, `volatile`, and `restrict`. It can be used in type declarations, type casts, type checks, and so on. It gets the type of a variable, function, or any C expression.
+
+The **`__typeof_unqual__`** keyword is a Microsoft-specific extension that provides the same functionality as **`typeof_unqual`**. The **`__typeof_unqual__`** keyword differs from `typeof_unqual` only in that it's available when compiling for all versions of C (not just `/std:clatest`), and it may ease porting code between other compilers that support `__typeof_unqual__`.
+
+### `typeof_unqual` syntax
+
+```c
+typeof_unqual(type)
+typeof_unqual(constant-expression)
+__typeof__unqual(constant-expression)
+```
+
+### `typeof_unqual` example
+
+This example uses `typeof_unqual()`, but the behavior is the same if you use `__typeof_unqual__`.
+
+```c
+// Compile with /std:clatest and /experimental:c11atomics
+#include <stdatomic.h>
+
+// A function that takes an atomic int pointer, but uses a non-atomic copy of the value
+void func(_Atomic(int) * pAtomic)
+{
+    typeof_unqual(*pAtomic) local = *pAtomic;
+
+    // Use local non-atomic copy of value
+}
+
+int main()
+{
+    int* const cpVar1 = 2;
+    typeof_unqual(cpVar1) pVar2 = 3;
+    pVar2 = 4; // no error because pi is not const. cpVar1 = 4 would be an error.
+
+    _Atomic(int)i = 42;
+    func(&i);
+
+    return 0;
+}
+```
+
+## Requirements
+
+Requires Visual Studio 17.9 or later, or `cl.exe` version 19.39.33428 or later.
+To use `typeof_unqual`, compile with [`/std:clatest`](../build/reference/std-specify-language-standard-version.md).
+
+## See also
+
+[`/std` (Specify Language Standard Version)](../build/reference/std-specify-language-standard-version.md)\

docs/overview/cpp-conformance-improvements.md

@@ -1,19 +1,59 @@
 ---
 title: "C++ conformance improvements in Visual Studio 2022"
 description: "Microsoft C++ in Visual Studio is improving standards conformance and fixing bugs regularly."
-ms.date: 12/07/2023
+ms.date: 2/6/2024
 ms.service: "visual-cpp"
 ms.subservice: "cpp-lang"
 ---
 # C++ Conformance improvements, behavior changes, and bug fixes in Visual Studio 2022
 
-Microsoft C/C++ in Visual Studio (MSVC) makes conformance improvements and bug fixes in every release. This article lists the significant improvements by major release, then by version. To jump directly to the changes for a specific version, use **In this article** links, above.
+Microsoft C/C++ in Visual Studio (MSVC) makes conformance improvements and bug fixes in every release. This article lists the significant improvements by major release, then by version. To jump directly to the changes for a specific version, use the **In this article** links.
 
 This document lists the changes in Visual Studio 2022.
 
-For a guide to the changes in Visual Studio 2019, see [C++ conformance improvements in Visual Studio 2019](cpp-conformance-improvements-2019.md).\
+For changes in Visual Studio 2019, see [C++ conformance improvements in Visual Studio 2019](cpp-conformance-improvements-2019.md).\
 For changes in Visual Studio 2017, see [C++ conformance improvements in Visual Studio 2017](cpp-conformance-improvements-2017.md).\
-For a complete list of previous conformance improvements, see [Visual C++ What's New 2003 through 2015](../porting/visual-cpp-what-s-new-2003-through-2015.md).
+For changes in older versions, see [Visual C++ What's New 2003 through 2015](../porting/visual-cpp-what-s-new-2003-through-2015.md).
+
+## <a name="improvements_179"></a> Conformance improvements in Visual Studio 2022 version 17.9
+
+Visual Studio 2022 version 17.9 contains the following conformance improvements, bug fixes, and behavior changes in the Microsoft C/C++ compiler.
+
+For a broader summary of changes made to the Standard Template Library, see [STL Changelog VS 2022 17.9](https://github.com/microsoft/STL/wiki/Changelog#vs-2022-179).
+
+### `__VA_OPT__` is enabled as an extension under `/Zc:preprocessor`
+
+`__VA_OPT__` was added to C++20 and C23. Previous to its addition, there wasn't a standard way to elide a comma in a variadic macro. To provide better backward compatibility, `__VA_OPT__` is enabled under the token based preprocessor `/Zc:preprocessor` across all language versions.
+
+For example, this now compiles without error:
+
+```cpp
+#define LOG_WRAPPER(message, ...) WRITE_LOG(__LINE__, message __VA_OPT__(, __VA_ARGS__))
+
+// Failed to build under /std:c11, now succeeds.
+LOG_WRAPPER("Log message");
+LOG_WRAPPER("Log message with %s", "argument")
+```
+
+### C23 language ###
+
+For C23, the following are available when using the `/std:clatest` compiler switch:
+
+[`typeof`](../c-language/typeof-c.md)\
+[`typeof_unqual`](../c-language/typeof-unqual-c.md)
+
+The following are available for all C language versions:
+
+[`__typeof__`](../c-language/typeof-c.md)\
+[`__typeof_unqual__`](../c-language/typeof-unqual-c.md)
+
+### C++ Standard Library
+
+**C++23 features**
+
+- `formattable`, `range_format`, `format_kind`, and `set_debug_format()` as part of [P2286R8 Formatting Ranges](https://wg21.link/P2286R8)
+- `<mdspan>` per [P0009R18](https://wg21.link/P0009R18) and subsequent wording changes that were applied to the C++23 Standard.
+- `format()` pointers per [P2510R3](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2510r3.pdf).
 
 ## <a name="improvements_178"></a> Conformance improvements in Visual Studio 2022 version 17.8
 
@@ -315,7 +355,7 @@ bidi.cpp(8): warning C5255: unterminated bidirectional character encountered: 'U
 
 ### `from_chars()` `float` tiebreaker
 
-Visual Studio 2022 version 17.2 fixes a bug in `<charconv>` `from_chars()` `float` tiebreaker rules that produced incorrect results. This bug affected decimal strings that were at the exact midpoint of consecutive `float` values, within a narrow range. (The smallest and largest affected values were `32768.009765625` and `131071.98828125`, respectively.) The tiebreaker rule wanted to round to "even," and "even" happened to be "down", but the implementation incorrectly rounded "up." (`double` was unaffected.) For more information and implementation details, see [microsoft/STL#2366](https://github.com/microsoft/STL/pull/2366).
+Visual Studio 2022 version 17.2 fixes a bug in `<charconv>` `from_chars()` `float` tiebreaker rules that produced incorrect results. This bug affected decimal strings that were at the exact midpoint of consecutive `float` values, within a narrow range. (The smallest and largest affected values were `32768.009765625` and `131071.98828125`, respectively.) The tiebreaker rule wanted to round to "even", and "even" happened to be "down", but the implementation incorrectly rounded "up" (`double` was unaffected.) For more information and implementation details, see [microsoft/STL#2366](https://github.com/microsoft/STL/pull/2366).
 
 This change affects runtime behavior in the specified range of cases:
 
@@ -483,7 +523,7 @@ int main(void)
 
 ### Error on a nondependent `static_assert`
 
-In Visual Studio 2022 version 17.1 and later, if the expression associated with a `static_assert` isn't a dependent expression, the compiler evaluates the expression when it is parsed. If the expression evaluates to `false`, the compiler emits an error. Previously, if the `static_assert` was within the body of a function template (or within the body of a member function of a class template), the compiler wouldn't perform this analysis.
+In Visual Studio 2022 version 17.1 and later, if the expression associated with a `static_assert` isn't a dependent expression, the compiler evaluates the expression when it's parsed. If the expression evaluates to `false`, the compiler emits an error. Previously, if the `static_assert` was within the body of a function template (or within the body of a member function of a class template), the compiler wouldn't perform this analysis.
 
 This change is a source breaking change. It applies in any mode that implies **`/permissive-`** or **`/Zc:static_assert`**.  This change in behavior can be disabled by using the **`/Zc:static_assert-`** compiler option.