Cause
A P/Invoke string parameter is passed by value and marked with System.Runtime.InteropServices.OutAttribute.
Rule description
The .NET runtime automatically performs string interning. If an interned string marked with System.Runtime.InteropServices.OutAttribute is passed by value to a P/Invoke, the runtime can be destabilized.
How to fix violations
If marshalling of modified string data back to the caller is required, pass the string by reference instead. Otherwise, the System.Runtime.InteropServices.OutAttribute can be removed without any other changes.
// Violation
[DllImport("MyLibrary")]
private static extern void Foo([Out] string s);
// Fixed: passed by reference
[DllImport("MyLibrary")]
private static extern void Foo(out string s);
// Fixed: marshalling data back to caller is not required
[DllImport("MyLibrary")]
private static extern void Foo(string s);When to suppress warnings
It is not safe to suppress a warning from this rule.