> On Sept. 1, 2015, 4:46 p.m., Joseph Wu wrote:
> > 3rdparty/libprocess/3rdparty/stout/include/stout/protobuf.hpp, lines 553-555
> > <https://reviews.apache.org/r/37826/diff/3/?file=1061137#file1061137line553>
> >
> >     Can you explain why this is a struct rather than a function?
> 
> Alexander Rukletsov wrote:
>     It's because we cannot partially specialize function templates and 
> overload won't work since we take the same argument. Do you think a comment 
> should be expanded?
> 
> Alexander Rukletsov wrote:
>     http://www.gotw.ca/publications/mill17.htm
> 
> Joseph Wu wrote:
>     Yes, I think a comment would be good regardless of how it ends up.
>     
>     What about using some C++11 type traits?  (But I'm not sure if this will 
> work.)
>     Something like:
>     ```
>     // Specialization for non-repeated fields.
>     template <typename T>
>     Try<T> parse(const JSON::Value& value,
>         typename std::enable_if<std::is_base_of<T, 
> google::protobuf::Message>, int>::type = 0) {...}
>     ```
>     
>     Note: This file uses some similar Boost type traits further up.
> 
> Alexander Rukletsov wrote:
>     I'm not sure how we can use type traits here. IIUC type traits facilitate 
> compile-time checks, and not compile-time dispatch. If we want to keep the 
> same function signature, we should rely on partial specialization. However, 
> we can still add these checks into `Parse<>::operator()` methods.

Which boils down to replacing
```
{ google::protobuf::Message* message = (T*) NULL; (void) message; }
```
with
```
static_assert(std::is_base_of<google::protobuf::Message, T>::value,
                  "T must be a protobuf message");
```
Does it make sense?


- Alexander


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On Sept. 1, 2015, 2:20 p.m., Alexander Rukletsov wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/37826/
> -----------------------------------------------------------
> 
> (Updated Sept. 1, 2015, 2:20 p.m.)
> 
> 
> Review request for mesos, Joseph Wu and Michael Park.
> 
> 
> Bugs: MESOS-3312
>     https://issues.apache.org/jira/browse/MESOS-3312
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> See summary.
> 
> 
> Diffs
> -----
> 
>   3rdparty/libprocess/3rdparty/stout/include/stout/protobuf.hpp 
> 57d5fdf45273c620655b44b5f5572290cffa4bf6 
> 
> Diff: https://reviews.apache.org/r/37826/diff/
> 
> 
> Testing
> -------
> 
> make check (Mac OS 10.10.4)
> 
> 
> Thanks,
> 
> Alexander Rukletsov
> 
>

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