65 lines
2.6 KiB
ReStructuredText
65 lines
2.6 KiB
ReStructuredText
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.. title:: clang-tidy - bugprone-compare-pointer-to-member-virtual-function
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bugprone-compare-pointer-to-member-virtual-function
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===================================================
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Detects unspecified behavior about equality comparison between pointer to member
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virtual function and anything other than null-pointer-constant.
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.. code-block:: c++
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struct A {
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void f1();
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void f2();
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virtual void f3();
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virtual void f4();
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void g1(int);
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};
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void fn() {
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bool r1 = (&A::f1 == &A::f2); // ok
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bool r2 = (&A::f1 == &A::f3); // bugprone
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bool r3 = (&A::f1 != &A::f3); // bugprone
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bool r4 = (&A::f3 == nullptr); // ok
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bool r5 = (&A::f3 == &A::f4); // bugprone
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void (A::*v1)() = &A::f3;
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bool r6 = (v1 == &A::f1); // bugprone
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bool r6 = (v1 == nullptr); // ok
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void (A::*v2)() = &A::f2;
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bool r7 = (v2 == &A::f1); // false positive, but potential risk if assigning other value to v2.
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void (A::*v3)(int) = &A::g1;
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bool r8 = (v3 == &A::g1); // ok, no virtual function match void(A::*)(int) signature.
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}
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Provide warnings on equality comparisons involve pointers to member virtual
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function or variables which is potential pointer to member virtual function and
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any entity other than a null-pointer constant.
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In certain compilers, virtual function addresses are not conventional pointers
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but instead consist of offsets and indexes within a virtual function table
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(vtable). Consequently, these pointers may vary between base and derived
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classes, leading to unpredictable behavior when compared directly. This issue
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becomes particularly challenging when dealing with pointers to pure virtual
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functions, as they may not even have a valid address, further complicating
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comparisons.
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Instead, it is recommended to utilize the ``typeid`` operator or other appropriate
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mechanisms for comparing objects to ensure robust and predictable behavior in
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your codebase. By heeding this detection and adopting a more reliable comparison
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method, you can mitigate potential issues related to unspecified behavior,
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especially when dealing with pointers to member virtual functions or pure
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virtual functions, thereby improving the overall stability and maintainability
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of your code. In scenarios involving pointers to member virtual functions, it's
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only advisable to employ ``nullptr`` for comparisons.
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Limitations
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-----------
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Does not analyze values stored in a variable. For variable, only analyze all virtual
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methods in the same ``class`` or ``struct`` and diagnose when assigning a pointer
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to member virtual function to this variable is possible.
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