docs/checks/README-copyable-polymorphic.md

0001 # copyable-polymorphic
0002
0003 Finds polymorphic classes that are copyable.
0004 Classes with virtual methods are usually handled by pointer, as passing
0005 then by value would allow up-casting to the base-class and slicing off the vtable.
0006 Example:
0007
0008 ```
0009 struct Base {
0010     virtual int getNumber() const { return 41; }
0011 };
0012
0013 struct Derived : public Base {
0014     int getNumber() const override { return 42; }
0015 };
0016
0017 void printNumber(Base b)
0018 {
0019     qDebug() << b.getNumber(); // Always prints 41!
0020 }
0021
0022 (...)
0023 Derived d;
0024 printNumber(d);
0025
0026 ```
0027
0028 To fix these warnings use `Q_DISABLE_COPY` or delete the copy-ctor yourself.
0029
0030 This check supports a fixit, however you'll need to set the env var
0031 CLAZY_ACCESSSPECIFIER_NON_QOBJECT=1. It's opt-in since it involves a bit of cpu
0032 overhead and is also responsible for bug #431186