[PATCH] D11940: don't diagnose -Wunused-parameter in virtual method or method that overrides base class method

[Nico Weber via cfe-commits]

Can't you just change your signature to

  virtual void a(int /* x */) {}

in these cases?

On Tue, Aug 11, 2015 at 6:43 AM, Daniel Marjamäki <
cfe-commits at lists.llvm.org> wrote:

> danielmarjamaki created this revision.
> danielmarjamaki added a reviewer: krememek.
> danielmarjamaki added a subscriber: cfe-commits.
>
> Don't diagnose -Wunused-parameter in methods that override other methods
> because the overridden methods might use the parameter
>
> Don't diagnose -Wunused-parameter in virtual methods because these might
> be overriden by other methods that use the parameter.
>
> Such diagnostics could be more accurately written if they are based on
> whole-program-analysis that establish if such parameter is unused in all
> methods.
>
>
>
> http://reviews.llvm.org/D11940
>
> Files:
>   lib/Sema/SemaDecl.cpp
>   test/SemaCXX/warn-unused-parameters.cpp
>
> Index: test/SemaCXX/warn-unused-parameters.cpp
> ===================================================================
> --- test/SemaCXX/warn-unused-parameters.cpp
> +++ test/SemaCXX/warn-unused-parameters.cpp
> @@ -32,3 +32,20 @@
>    auto l = [&t...]() { return sizeof...(s); };
>    return l();
>  }
> +
> +// Don't diagnose virtual methods or methods that override base class
> +// methods.
> +class Base {
> +public:
> +  virtual void f(int x);
> +};
> +
> +class Derived : public Base {
> +public:
> +  // Don't warn in overridden methods.
> +  virtual void f(int x) {}
> +
> +  // Don't warn in virtual methods.
> +  virtual void a(int x) {}
> +};
> +
> Index: lib/Sema/SemaDecl.cpp
> ===================================================================
> --- lib/Sema/SemaDecl.cpp
> +++ lib/Sema/SemaDecl.cpp
> @@ -10797,8 +10797,13 @@
>
>      if (!FD->isInvalidDecl()) {
>        // Don't diagnose unused parameters of defaulted or deleted
> functions.
> -      if (!FD->isDeleted() && !FD->isDefaulted())
> -        DiagnoseUnusedParameters(FD->param_begin(), FD->param_end());
> +      if (!FD->isDeleted() && !FD->isDefaulted()) {
> +        // Don't diagnose unused parameters in virtual methods or
> +        // in methods that override base class methods.
> +        const auto MD = dyn_cast<CXXMethodDecl>(FD);
> +        if (!MD || (MD->size_overridden_methods() == 0U &&
> !MD->isVirtual()))
> +          DiagnoseUnusedParameters(FD->param_begin(), FD->param_end());
> +      }
>        DiagnoseSizeOfParametersAndReturnValue(FD->param_begin(),
> FD->param_end(),
>                                               FD->getReturnType(), FD);
>
>
>
>
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