[clang-tidy] new cppcoreguidelines-slicing

Flags slicing of member variables or vtable. See:

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#es63-dont-slice
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c145-access-polymorphic-objects-through-pointers-and-references

Differential revision:
http://reviews.llvm.org/D21974

llvm-svn: 276408

1 files changed, 23 insertions, 0 deletions

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+.. title:: clang-tidy - cppcoreguidelines-slicing
+
+cppcoreguidelines-slicing
+=========================
+
+Flags slicing of member variables or vtable. Slicing happens when copying a
+derived object into a base object: the members of the derived object (both
+member variables and virtual member functions) will be discarded.
+This can be misleading especially for member function slicing, for example:
+
+.. code:: c++
+
+	struct B { int a; virtual int f(); };
+	struct D : B { int b; int f() override; };
+	void use(B b) {  // Missing reference, intended ?
+	  b.f();  // Calls B::f.
+	}
+	D d;
+	use(d);  // Slice.
+
+See the relevant CppCoreGuidelines sections for details:
+https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#es63-dont-slice
+https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c145-access-polymorphic-objects-through-pointers-and-references