[LLVMdev] Final added to parser<bool>

[reed kotler]

//===----------------------------------------------------------------------===//
// FalseParser
//===----------------------------------------------------------------------===//
class FalseParser : public parser<bool> {
  public:
   explicit FalseParser(Option &O) : parser<bool>(O) { }

   // parse - Return true on error.
   bool parse(cl::Option& O, StringRef ArgName, StringRef Arg, bool& Val) {
     if (cl::parser<bool>::parse(O, ArgName, Arg, Val))
       return false;
     Val = false;
     return false;
   }
};

I don't know the history of this. I'm just starting to do some mclinker 
work to add the new mips r6 relocations to it.

On 03/18/2015 07:00 PM, David Blaikie wrote:
>
>
> On Wed, Mar 18, 2015 at 6:48 PM, reed kotler <rkotler at mips.com 
> <mailto:rkotler at mips.com>> wrote:
>
>     Hi David,
>
>     Is there a reason that we need to have "final" for parser<bool> ???
>
>
> Clang has a (reasonable) warning for types with virtual functions and 
> a non-virtual dtor. This warning is suppressed if the dtor is 
> protected or the class is final (since in the first case it's clear 
> that the user intends not to destroy objects via base pointers, only 
> derived ones - and in the second case there's no risk of derived 
> classes, so public access to the dtor is safe even without virtual 
> dispatch.
>
> Since the parser hierarchy never needed polymorphic destruction (all 
> instances are concrete instances of derived classes owned and 
> destroyed directly, not via base pointers) this seemed like a fine way 
> to structure the API.
>
>     This breaks the compilation of mclinker which derives a class from
>     this.
>
>     In file included from
>     /home/rkotler/workspace/mclinker/lib/Support/CommandLine.cpp:9:0:
>     /home/rkotler/workspace/mclinker/include/mcld/Support/CommandLine.h:49:7:
>     error: cannot derive from ‘final’ base ‘llvm::cl::parser<bool>’ in
>     derived type ‘llvm::cl::FalseParser’
>
>
> Why is it being derived from? If it's just a typedef that's required, 
> it might be more appropriate to use a typedef instead of derivation.
>
>     make[2]: *** [Support/CommandLine.o] Error 1
>     make[2]: Leaving directory `/home/rkotler/mclinker_build/lib'
>     make[1]: *** [all] Error 2
>     make[1]: Leaving directory `/home/rkotler/mclinker_build/lib'
>     make: *** [all-recursive] Error 1
>
>
>
>     Reed
>
>

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