Merging changes synced from https://github.com/MicrosoftDocs/cpp-docs-pr (branch live)

Author: Learn Build Service GitHub App

docs/code-quality/c6001.md

@@ -37,7 +37,7 @@ To correct this warning, initialize the variable as shown in the following code:
 ```cpp
 int f( bool b )
 {
-   int i= -1;
+   int i = -1;
 
    if ( b )
    {
@@ -47,6 +47,57 @@ int f( bool b )
 }
 ```
 
+## Heuristics
+
+Variables are also considered initialized when they're passed by reference to
+another function. Thus, the following example would also consider `i` to be
+initialized.
+
+```cpp
+void init( int& i );
+
+int f( bool b )
+{
+   int i;
+
+   init(i);
+
+   if ( b )
+   {
+      i = 0;
+   }
+   return i; // i is assumed to be initialized by init(i)
+}
+```
+
+This is to support the pattern of passing a pointer to a variable into
+an initialization function.
+
+Since many functions expect pointers to point to initialized data already, this
+heuristic can lead to false negatives. [SAL annotations] such as `_In_` and
+`_Out_` can be used to more precisely describe a function's behavior. For
+example, in the following we call an external function that expects its argument
+to already be initialized and the warning is still generated.
+
+```cpp
+void use( _In_ int& i );
+
+int f( bool b )
+{
+   int i;
+
+   use(i); // uninitialized variable warning because of _In_ annotation on use
+
+   if ( b )
+   {
+      i = 0;
+   }
+   return i;
+}
+```
+
+[SAL annotations]: ./annotating-function-parameters-and-return-values.md
+
 ## See also
 
 [Compiler Warning (level 1 and level 4) C4700](../error-messages/compiler-warnings/compiler-warning-level-1-and-level-4-c4700.md)