[clang] [clang][analyzer doc] Add basic description of checker 'core.CallAndMessage' (NFC). (PR #177179)

[Balázs Kéri via cfe-commits]

https://github.com/balazske created https://github.com/llvm/llvm-project/pull/177179

The checker had very little documentation. Now a more detailed (but still not much) description of the features and options is added.

>From 982a6b1aafaf6eb5e644a4e02710e73d5447957a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bal=C3=A1zs=20K=C3=A9ri?= <balazs.keri at ericsson.com>
Date: Wed, 21 Jan 2026 15:16:58 +0100
Subject: [PATCH] [clang][analyzer doc] Add basic description of checker
 'core.CallAndMessage' (NFC).

The checker had very little documentation. Now a more detailed (but still
not much) description of the features and options is added.
---
 clang/docs/analyzer/checkers.rst | 43 +++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index 31edf9e99dc7d..ae9c1dea14d55 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -83,7 +83,48 @@ Ensure the shift operands are in proper range before shifting.
 
 core.CallAndMessage (C, C++, ObjC)
 """"""""""""""""""""""""""""""""""
- Check for logical errors for function calls and Objective-C message expressions (e.g., uninitialized arguments, null function pointers).
+Check for logical errors for function calls and Objective-C message expressions
+(e.g., uninitialized arguments, null function pointers).
+
+This checker is a collection of related checks that can be turned on or off by
+checker options.
+
+* **FunctionPointer** Check for null or undefined function pointer at function
+  call.
+* **CXXThisMethodCall** Check for null or undefined ``this`` pointer at method
+  call.
+* **CXXDeallocationArg** Check for null or undefined argument of
+  ``operator delete``.
+* **ArgInitializedness** Check for undefined pass-by-value function arguments.
+* **ArgPointeeInitializedness** Check for undefined pass-by-reference (pointer
+  to constant value or constant reference) function arguments. In special cases
+  non-constant arguments are checked. This happens for C library functions where
+  it is required to initialize (at least partially) a passed structure which
+  is used for both input and output (for example last argument of ``mktime`` or
+  ``mbrlen``).
+* **ParameterCount** Check for correct number of passed arguments to functions
+  or ObjC blocks. This will warn if the actual argument count is less than the
+  required count (by the declaration).
+* **NilReceiver** Check whether the receiver in a message expression is ``nil``.
+* **UndefReceiver** Check whether the receiver in a message expression is
+  undefined.
+
+For example to turn off the check for parameter count, set the checker option
+``ParameterCount`` to ``false``. By default all of these checks is enabled
+except **ArgPointeeInitializedness** because this check is more likely to
+produce false positives.
+
+**Additional options**
+
+* **ArgPointeeInitializednessComplete** Controls when to emit the warning at the
+  **ArgPointeeInitializedness** check. If set to ``true`` the warning will be
+  emitted if any member of the passed structure is not initialized. If set to
+  ``false`` the warning is emitted only if all members (the complete structure)
+  are not initialized. The default is ``false``. (Arguments of C library
+  functions which require initialization are always checked as if the option
+  would be ``false``.)
+
+**Some examples**
 
 .. literalinclude:: checkers/callandmessage_example.c
     :language: objc