[clang] [NFC][rtsan] Docs of how to disable rtsan (PR #107707)

[Chris Apple via cfe-commits]

https://github.com/cjappl updated https://github.com/llvm/llvm-project/pull/107707

>From e3e211f65afbc923299c0f413d2c50c7b00884b6 Mon Sep 17 00:00:00 2001
From: Chris Apple <cja-private at pm.me>
Date: Sat, 7 Sep 2024 08:38:06 -0700
Subject: [PATCH 1/3] [NFC][rtsan] Docs of how to disable rtsan

---
 clang/docs/RealtimeSanitizer.rst | 50 ++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/clang/docs/RealtimeSanitizer.rst b/clang/docs/RealtimeSanitizer.rst
index 799cd43509c6e6..7854cd3c0331a4 100644
--- a/clang/docs/RealtimeSanitizer.rst
+++ b/clang/docs/RealtimeSanitizer.rst
@@ -83,3 +83,53 @@ non-zero exit code.
     #13 0x00010230dd64 in main main.cpp:9
     #14 0x0001958960dc  (<unknown module>)
     #15 0x2f557ffffffffffc  (<unknown module>)
+
+Disabling
+---------
+
+In some circumstances, you may want to suppress RealtimeSanitizer violations in a specific scope.
+
+In C++, this is achieved via  ``__rtsan::ScopedDisabler``. Within the scope where the ``ScopedDisabler`` object is instantiated, all sanitizer-reported violations are suppressed. This suppression applies to the current scope as well as all invoked functions, including any functions called transitively. 
+
+.. code-block:: c++
+
+    #include <sanitizer/rtsan_interface.h>
+
+    void process(const std::vector<float>& buffer) [[clang::nonblocking]] {
+        {
+            __rtsan::ScopedDisabler d;
+            ...
+        }
+    }
+
+If RealtimeSanitizer is not enabled at compile time (i.e., the code is not compiled with the ``-fsanitize=realtime`` flag), the ``ScopedDisabler`` is compiled as a no-op.
+
+In C, you can use the ``__rtsan_disable()`` and ``rtsan_enable()`` functions to manually disable and re-enable RealtimeSanitizer checks. 
+
+.. code-block:: c++
+
+    #include <sanitizer/rtsan_interface.h>
+
+    int process(const float* buffer) [[clang::nonblocking]]
+    {
+        {
+            __rtsan_disable();
+
+            ...
+
+            __rtsan_enable();
+        }
+    }
+
+Each call to ``__rtsan_disable()`` must be paired with a subsequent call to ``__rtsan_enable()`` to restore normal sanitizer functionality. If a corresponding ``rtsan_enable()`` call is not made, undefined behavior may result, potentially leaving the sanitizer permanently disabled for the rest of the program's execution.
+
+Compile-time sanitizer detection
+--------------------------------
+
+Clang provides the pre-processor macro ``__has_feature`` which may be used to detect if RealtimeSanitizer is enabled at compile-time.
+
+.. code-block:: c++
+
+    #if defined(__has_feature) && __has_feature(realtime_sanitizer)
+    ...
+    #endif

>From e6fe535a6453c8599c5325d12adeed48e39a2c65 Mon Sep 17 00:00:00 2001
From: Chris Apple <cja-private at pm.me>
Date: Mon, 9 Sep 2024 12:51:11 -0700
Subject: [PATCH 2/3] [PR] david - better wording of what is suppressed

---
 clang/docs/RealtimeSanitizer.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/docs/RealtimeSanitizer.rst b/clang/docs/RealtimeSanitizer.rst
index 7854cd3c0331a4..b08bd30a83434f 100644
--- a/clang/docs/RealtimeSanitizer.rst
+++ b/clang/docs/RealtimeSanitizer.rst
@@ -87,9 +87,9 @@ non-zero exit code.
 Disabling
 ---------
 
-In some circumstances, you may want to suppress RealtimeSanitizer violations in a specific scope.
+In some circumstances, you may want to suppress error reporting in a specific scope.
 
-In C++, this is achieved via  ``__rtsan::ScopedDisabler``. Within the scope where the ``ScopedDisabler`` object is instantiated, all sanitizer-reported violations are suppressed. This suppression applies to the current scope as well as all invoked functions, including any functions called transitively. 
+In C++, this is achieved via  ``__rtsan::ScopedDisabler``. Within the scope where the ``ScopedDisabler`` object is instantiated, all sanitizer error reports are suppressed. This suppression applies to the current scope as well as all invoked functions, including any functions called transitively. 
 
 .. code-block:: c++
 

>From 84232e61c504c279eac7555a852e1d11d7253407 Mon Sep 17 00:00:00 2001
From: Chris Apple <cja-private at pm.me>
Date: Mon, 9 Sep 2024 14:06:16 -0700
Subject: [PATCH 3/3] [PR] vitalybuka - leaving undefined behaviour ACTUALLY
 undefined

---
 clang/docs/RealtimeSanitizer.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/docs/RealtimeSanitizer.rst b/clang/docs/RealtimeSanitizer.rst
index b08bd30a83434f..5e281a2a357907 100644
--- a/clang/docs/RealtimeSanitizer.rst
+++ b/clang/docs/RealtimeSanitizer.rst
@@ -121,7 +121,7 @@ In C, you can use the ``__rtsan_disable()`` and ``rtsan_enable()`` functions to
         }
     }
 
-Each call to ``__rtsan_disable()`` must be paired with a subsequent call to ``__rtsan_enable()`` to restore normal sanitizer functionality. If a corresponding ``rtsan_enable()`` call is not made, undefined behavior may result, potentially leaving the sanitizer permanently disabled for the rest of the program's execution.
+Each call to ``__rtsan_disable()`` must be paired with a subsequent call to ``__rtsan_enable()`` to restore normal sanitizer functionality. If a corresponding ``rtsan_enable()`` call is not made, the behavior is undefined.
 
 Compile-time sanitizer detection
 --------------------------------