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

[Zachary Turner]

Yes, sorry for the confusion.  There's a totally new review up.  I
commented in this thread yesterday saying that I uploaded a new review, but
since it was completely different it was in a new issue entirely.  Then
comments about that review started coming in on this thread.  Anyway, look
here: http://reviews.llvm.org/D5198


On Fri, Sep 5, 2014 at 4:35 PM, Todd Fiala <tfiala at google.com> wrote:

> 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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