Merge pull request #6119 from TylerMSFT/warningdirective

new article for #warning

Author: Stacyrch140

docs/preprocessor/hash-error-directive-c-cpp.md

@@ -4,11 +4,10 @@ title: "#error directive (C/C++)"
 ms.date: "08/29/2019"
 f1_keywords: ["#error"]
 helpviewer_keywords: ["#error directive", "preprocessor, directives", "error directive (#error directive)"]
-ms.assetid: d550a802-ff19-4347-9597-688935d23b2b
 ---
 # #error directive (C/C++)
 
-The **#error** directive emits a user-specified error message at compile time, and then terminates the compilation.
+The `#error` directive emits a user-specified error message at compile time. Then it terminates the compilation.
 
 ## Syntax
 
@@ -26,4 +25,5 @@ The error message that this directive emits includes the *token-string* paramete
 
 ## See also
 
-[Preprocessor directives](../preprocessor/preprocessor-directives.md)
+[Preprocessor directives](../preprocessor/preprocessor-directives.md)\
+[#warning directive](../preprocessor/hash-warning-directive-c-cpp.md)

docs/preprocessor/hash-warning-directive-c-cpp.md

@@ -0,0 +1,33 @@
+---
+description: "Learn more about: #warning directive (C/C++)"
+title: "#warning directive (C/C++)"
+ms.date: 10/15/2025
+f1_keywords: ["#warning"]
+helpviewer_keywords: ["#warning directive", "preprocessor, directives", "warning directive (#warning directive)"]
+---
+# #warning directive (C/C++)
+
+The **#warning** directive emits a user-specified warning message at compile time. It doesn't stop compilation. This directive is available starting in C23 and C++23.
+
+## Syntax
+
+> **#warning** *token-string*
+
+## Remarks
+
+The warning message is the *token-string* parameter. The *token-string* parameter isn't subject to macro expansion and can be optionally enclosed in quotes.
+
+Use this directive to inform the developer of a nonfatal issue or to communicate other important information during compilation.
+
+The following example shows how to use the **#warning** directive:
+
+```cpp
+#if defined(_LEGACY_FEATURE_FLAG)
+#warning "_LEGACY_FEATURE is deprecated and should not be used."
+#endif
+```
+
+## See also
+
+[Preprocessor directives](../preprocessor/preprocessor-directives.md)\
+[#error directive](../preprocessor/hash-error-directive-c-cpp.md)

docs/preprocessor/preprocessor-directives.md

@@ -1,13 +1,12 @@
 ---
 description: "Learn more about: Preprocessor directives"
 title: "Preprocessor directives"
-ms.date: "08/29/2019"
+ms.date: 10/15/2025
 helpviewer_keywords: ["directives, preprocessor", "preprocessor, directives"]
-ms.assetid: e0fc4564-b6cf-4a36-bf51-6ccd7abd0a94
 ---
 # Preprocessor directives
 
-Preprocessor directives, such as `#define` and `#ifdef`, are typically used to make source programs easy to change and easy to compile in different execution environments. Directives in the source file tell the preprocessor to take specific actions. For example, the preprocessor can replace tokens in the text, insert the contents of other files into the source file, or suppress compilation of part of the file by removing sections of text. Preprocessor lines are recognized and carried out before macro expansion. Therefore, if a macro expands into something that looks like a preprocessor command, it isn't recognized by the preprocessor.
+Preprocessor directives, such as `#define` and `#ifdef`, are used to make source programs easy to change and compile in different execution environments. Directives in the source file tell the preprocessor to take specific actions. For example, the preprocessor can replace tokens in the text, insert the contents of other files into the source file, or suppress compilation of part of the file by removing sections of text. Preprocessor directives are processed before macro expansion. Therefore, if a macro expands into something that looks like a preprocessor command, it isn't recognized by the preprocessor.
 
 Preprocessor statements use the same character set as source file statements, with the exception that escape sequences aren't supported. The character set used in preprocessor statements is the same as the execution character set. The preprocessor also recognizes negative character values.
 
@@ -29,7 +28,8 @@ The preprocessor recognizes the following directives:
    :::column span="":::
       [`#import`](../preprocessor/hash-import-directive-cpp.md)\
       [`#include`](../preprocessor/hash-include-directive-c-cpp.md)\
-      [`#line`](../preprocessor/hash-line-directive-c-cpp.md)
+      [`#line`](../preprocessor/hash-line-directive-c-cpp.md)\
+      [`#warning`](../preprocessor/hash-warning-directive-c-cpp.md)
    :::column-end:::
    :::column span="":::
       [`#pragma`](../preprocessor/pragma-directives-and-the-pragma-keyword.md)\

docs/preprocessor/toc.yml

@@ -92,6 +92,8 @@ items:
           href: ../preprocessor/hash-undef-directive-c-cpp.md
         - name: "#using directive (C++/CLI)"
           href: ../preprocessor/hash-using-directive-cpp.md
+        - name: "#warning directive (C/C++)"
+          href: ../preprocessor/hash-warning-directive-c-cpp.md
     - name: Preprocessor operators
       expanded: false
       items: