[Lldb-commits] [PATCH] Implements a HostThread class.

[Todd Fiala]

Hey Zachary - am I looking in the right spot?  The top of the thread is
talking about this:

http://reviews.llvm.org/D5110

You said this:

> Latest version is up, should address all the issues pointed out in yoru
comments.

Which leads me to believe I would see multiple versions of it.  I'm only
seeing the August patch on reviews.llvm.org.  What am I missing?  (I'm
guessing it's the wrong review?)

-Todd


On Fri, Sep 5, 2014 at 3:31 PM, Zachary Turner <zturner at google.com> wrote:

> Latest version is up, should address all the issues pointed out in yoru
> comments.  I didn't actually address the HostThread::GetName() issue in
> this patch, because it turns out we only ever attempt to get the thread
> name in one place, and it's of the current thread.  I still am fine
> changing this, but the CL is already pretty huge and it didn't seem too
> urgent for the purposes of this change.
>
>
> On Fri, Sep 5, 2014 at 9:17 AM, <jingham at apple.com> wrote:
>
>> Yes, the "alternate" method sounds fine to me as well.
>>
>> Jim
>>
>>
>> > On Sep 4, 2014, at 6:35 PM, Zachary Turner <zturner at google.com> wrote:
>> >
>> > Come to think of it I actually like my "alternate" method more than the
>> way I've done it, because it means I don't need to duplicate handles in the
>> assignment / copy-constructor of HostThreadWindows, because the only thing
>> that will get copied is the shared_ptr.
>> >
>> >
>> > On Thu, Sep 4, 2014 at 6:18 PM, Zachary Turner <zturner at google.com>
>> wrote:
>> >
>> >
>> >
>> > On Thu, Sep 4, 2014 at 6:06 PM, <jingham at apple.com> wrote:
>> >
>> > > On Sep 4, 2014, at 5:57 PM, Zachary Turner <zturner at google.com>
>> wrote:
>> > >
>> > > Regarding point #1: I'm still not sold on this.  Exposing only the
>> HostThreadBase really complicates some things.  Some of the issues escape
>> my mind right now, but one in particular stands out.  There are a couple of
>> places where threads are copied.  I don't remember the exact file off the
>> top of my head, but something about making a copy of a thread in case the
>> thread is shutting down and nulls itself out.  With a pointer or reference
>> to a base class, this can't be done without a virtual Clone() method, which
>> is really kind of gross.
>> >
>> > I would like to see what is hard.  You are using a generic factory to
>> make the HostThreads, your ThreadRunner, and then you are calling generic
>> methods on them.  Maybe I'm too stuck on this, but it seems like we should
>> keep host specific stuff out of generic lldb functionality, and enforce
>> that with the compiler, not with buildbots on the lacking host failing
>> sometime later on...  That just seems ugly to me.
>> >
>> > It's not that it's hard, I guess it's just a difference of opinion on
>> what's the most ugly.  Consider the following block of code which uses raw
>> lldb:thread_t's.
>> >
>> > lldb::thread_t backup = m_thread;
>> > ...
>> > m_thread = backup;
>> >
>> > With my patch, that becomes the following:
>> >
>> > HostThread backup = m_thread;
>> > ...
>> > m_thread = backup;
>> >
>> > With the base class method, that becomes the following:
>> >
>> > HostThreadBaseSP backup = m_thread->Clone();
>> > ...
>> > m_thread = backup->Clone();
>> >
>> > These look similar, but behind the scenes it's ugly.  You now need a
>> pure virtual Clone() method on HostThreadBase (trivial to implement of
>> course, but it's just code pollution).  You need to store by pointer
>> instead of by value, which means you have to worry about null-checks as
>> well.
>> >
>> > There is the issue you mention which is that only a buildbot will tell
>> you if you use a platform-specific method, but my argument is just that
>> this is strictly better than before, because before *nobody* would tell you
>> when you used a platform-specific method.  It would just be a no-op.
>> >
>> > That said, I have another idea in case you're still opposed to the way
>> I've done it.  Basically, just have HostThread.  Nothing derives from it.
>> Its only member is a shared_ptr<HostNativeThread>.  HostNativeThread does
>> have subclasses just as the current HostThreadBase does.  The methods of
>> HostThread just forward their calls to HostNativeThread, but also
>> HostThread provides a method called GetNativeThread() which returns
>> HostNativeThread automatically cast to the most-derived type.
>> >
>> > This way, in generic code, as long as you don't write
>> thread.GetNativeThread(), you're guaranteed to only be using generic
>> methods.
>> >
>>
>>
>
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-- 
Todd Fiala | Software Engineer | tfiala at google.com | 650-943-3180
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