llvm dev - Aug 2018 - ArgList flag values

I've come across a need to know whether an option was set true, false or
unspecified.  If it is true I want to do one thing, if it is false I
want to do something else and if it is unspecified I want to do nothing.

ArgList::hasFlag is a convenient way to check true/false with a default
value.  An ArgList::hasFlag that returned Optional<bool> would allow
checking the unspecified case.  Returning some kind Tribool class object
would allow the same.

Both Optional<bool> and Tribool are somewhat overkill for this kind of
thing as I really wouldn't need to do comparisons and logical operations
on the value.  A three-state enum (class) would do just as well.

Is there an existing way to handle this kind of flag?  If not, would
there be interest in adding support for it?

                         -David

> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
David
> Greene via llvm-dev
> Sent: Thursday, August 09, 2018 5:28 PM
> To: llvm-dev at lists.llvm.org
> Subject: [llvm-dev] ArgList flag values
> 
> I've come across a need to know whether an option was set true, false
or
> unspecified.  If it is true I want to do one thing, if it is false I
> want to do something else and if it is unspecified I want to do nothing.
> 
> ArgList::hasFlag is a convenient way to check true/false with a default
> value.  An ArgList::hasFlag that returned Optional<bool> would allow
> checking the unspecified case.  Returning some kind Tribool class object
> would allow the same.
> 
> Both Optional<bool> and Tribool are somewhat overkill for this kind
of
> thing as I really wouldn't need to do comparisons and logical
operations
> on the value.  A three-state enum (class) would do just as well.
> 
> Is there an existing way to handle this kind of flag?  If not, would
> there be interest in adding support for it?
I'd be inclined to use getLastArg for this, which returns nullptr if you
don't have any of the specified options.
--paulr
> 
>                          -David
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> llvm-dev at lists.llvm.org
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<paul.robinson at sony.com> writes:
>> ArgList::hasFlag is a convenient way to check true/false with a default
>> value.  An ArgList::hasFlag that returned Optional<bool> would
allow
>> checking the unspecified case.  Returning some kind Tribool class
object
>> would allow the same.
>
> I'd be inclined to use getLastArg for this, which returns nullptr if
you
> don't have any of the specified options.
Thanks for the pointer!

                           -David