On 07/20/2017 10:35 AM, Volker Reichelt wrote:
Hi,
the following patch introduces a new C++ warning option
-Wduplicated-access-specifiers that warns about redundant
access-specifiers in classes, e.g.
class B
{
public:
B();
private:
void foo();
private:
int i;
};
I'm very fond of warnings that help find real bugs, or even that
provide an opportunity to review code for potential problems or
inefficiencies and suggest a possibility to improve it in some
way (make it clearer, or easier for humans or compilers to find
real bugs in, or faster, etc.), even if the code isn't strictly
incorrect.
In this case I'm having trouble coming up with an example where
the warning would have this effect. What do you have in mind?
(Duplicate access specifiers tend to crop up in large classes
and/or as a result of preprocessor conditionals.)
Btw., there are examples of poor coding practices where I can
imagine a warning focused on access specifiers being helpful.
For instance, a class whose member functions maintain non-trivial
invariants among its data members should declare the data private
to prevent clients from inadvertently breaking those invariants.
A specific example might be a container class (like string or
vector) that owns the block of memory it allocates. A warning
that detected when such members are publicly accessible could
help improve encapsulation. I suspect this would be challenging
to implement and would likely require some non-trivial analysis
in the middle end.
Another example is a class that defines an inaccessible member
that isn't used (e.g., class A { int i; }; that Clang detects
with -Wunused-private-field; or class A { void f () { } };).
I would expect this to be doable in the front end.
Martin
