Document -Wtautological-pointer-compare & -Wtautological-undefined-compare with example

git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_35@215651 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index c7c701be9950337a10092b4b2113446c11c348d6..995f906534c0a4c9718187aa1d56b6fc7770354c 100644 (file)
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -70,6 +70,38 @@ about them. The improvements since the 3.4 release include:
 - New warning `-Wabsolute-value`: Clang warns about incorrect or useless usage
   of the absolute functions (`abs`, `fabsf`, etc).
 
+- New warning `-Wtautological-pointer-compare`:
+
+  .. code-block:: c++
+
+    #include <stddef.h>
+    void foo() {
+     int arr[5];
+     int x;
+     // warn on these conditionals
+     if (foo);
+     if (arr);
+     if (&x);
+     if (foo == NULL);
+     if (arr == NULL);
+     if (&x == NULL);
+    }
+
+  returns
+  `warning: comparison of address of 'x' equal to a null pointer is always false [-Wtautological-pointer-compare]`
+
+- New warning `-Wtautological-undefined-compare`: 
+
+  .. code-block:: c++
+
+    #include <stddef.h>
+    void f(int &x) {
+       if (&x == nullptr) { }
+    }
+
+  returns
+  `warning: reference cannot be bound to dereferenced null pointer in well-defined C++ code; comparison may be assumed to always evaluate to false [-Wtautological-undefined-compare]`
+
 -  ...
 
 New Compiler Flags