================
@@ -0,0 +1,232 @@
+// RUN: %check_clang_tidy %s bugprone-unsafe-crtp %t
+
+namespace class_implicit_ctor {
+template <typename T>
+class CRTP {};
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: the implicit default constructor
of the CRTP is publicly accessible [bugprone-unsafe-crtp]
+// CHECK-MESSAGES: :[[@LINE-2]]:7: note: consider making it private
+// CHECK-FIXES: CRTP() = default;
+
+class A : CRTP<A> {};
+} // namespace class_implicit_ctor
+
+namespace class_uncostructible {
+template <typename T>
+class CRTP {
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: the CRTP cannot be constructed
from the derived class [bugprone-unsafe-crtp]
+// CHECK-MESSAGES: :[[@LINE-2]]:7: note: consider declaring the derived class
as friend
+// CHECK-FIXES: friend T;
----------------
isuckatcs wrote:
I don't see how a factory function in a CRTP context would make sense. If the
only constructor is for a static factory function, which is unaccessible by the
derived class, then the derived class cannot be constructed either, right? Also
since the goal of the CRTP is to provide some functionality to it's template
parameter, having a factory method would just result in instantiating it on
it's own, which also doesn't make sense, right?
Otherwise since the goal is to prevent any kind of accidental instantiation,
the check assumes that every other constructor is private, and then we need the
friend, since the derived class has no way to instantiate the CRTP. If anything
else other than the derived class and the CRTP itself has access to the
constructors, then accidental instantiation can happen, which we want to
prevent.
If the class only provides static methods, then why would any other class
inherit from it, or use it as a CRTP?
https://github.com/llvm/llvm-project/pull/82403
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