[clang] [Clang][analyzer] add documentation for optin performance padding (padding checker) #73675 (PR #86411)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (komalverma04)

<details>
<summary>Changes</summary>

# Added documentation for optin.performance.Padding.
- Performance package has `PaddingChecker` checker.
- It checks for excessively padded structs.
   - It has one option that is `AllowedPad`, an integer option.
   - It's default value is 24 bytes.
      - Reports are generated when padding exceeds `AllowedPad`.
 ## Purpose
The purpose of this pull request is to improve the clarity and completeness of the documentation for PaddingChecker in the optin.performance.Padding checker.

Closes #<!-- -->73675

---
Full diff: https://github.com/llvm/llvm-project/pull/86411.diff


2 Files Affected:

- (modified) clang/docs/analyzer/checkers.rst (+20-2) 
- (modified) clang/include/clang/StaticAnalyzer/Checkers/Checkers.td (+1-1) 


``````````diff
diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index fe211514914272..64b09bc6ecd1d8 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -804,10 +804,28 @@ Check for performance anti-patterns when using Grand Central Dispatch.
 
 .. _optin-performance-Padding:
 
-optin.performance.Padding
-"""""""""""""""""""""""""
+optin.performance.Padding (PaddingChecker)
+"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
 Check for excessively padded structs.
 
+.. code-block:: objc
+
+ struct TestStruct {
+      int data1;   // 4 bytes
+      char data2;  // 1 byte
+      char padding[27];  // 27 bytes of padding
+    };  // Total size: 32 bytes 
+  
+  void TestFunction() {
+      struct TestStruct struct1;  // Warning is generated due to excessive padding.
+    }
+
+   // Reports are only generated if the excessive padding exceeds 'AllowedPad' in bytes.
+
+  // AllowedPad: Default Value: 24 bytes
+
+   Usage: `AllowedPad=<value>`
+
 .. _optin-portability-UnixAPI:
 
 optin.portability.UnixAPI
diff --git a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
index 686e5e99f4a62c..c0e4e9a70c2ef3 100644
--- a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -908,7 +908,7 @@ def PaddingChecker : Checker<"Padding">,
                   "24",
                   Released>
   ]>,
-  Documentation<NotDocumented>;
+  Documentation<HasDocumentation>;
 
 } // end: "padding"
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/86411