Re: [PATCH 3/3] matching tokens: C++ parts

[Martin Sebor <msebor@gmail.com>]

On 07/12/2017 07:13 AM, Trevor Saunders wrote:
> On Tue, Jul 11, 2017 at 11:24:45AM -0400, David Malcolm wrote:
>> +/* Some tokens naturally come in pairs e.g.'(' and ')'.
>> +   This class is for tracking such a matching pair of symbols.
>> +   In particular, it tracks the location of the first token,
>> +   so that if the second token is missing, we can highlight the
>> +   location of the first token when notifying the user about the
>> +   problem.  */
>> +
>> +template <typename token_pair_traits_t>
>
> the style guide says template arguments should be in mixed case, so
> TokenPairTraits, and the _t looks odd to my eyes.
>
>> +class token_pair
>> +{
>> + private:
>> +  typedef token_pair_traits_t traits_t;
>
> I'm not really sure what this is about, you can name it whatever you
> like as a template argument, and this name seems less descriptive of
> what its about.

In generic code, a typedef for a template parameter makes it
possible to refer to the parameter even when it's a member of
a type whose template parameters aren't known (or that's not
even a template).  In the C++ standard library the naming
convention is to end such typedefs with _type (e.g., value_type,
allocator_type, etc.)  GCC itself makes use of this convention
in its hash_table template. (I have no idea if token_pair is
ever used in type generic contexts where the typedef is needed.)

As an aside, it's interesting to note that names that end in _t
are reserved by POSIX, so (purely) pedantically speaking, making
use of them for own symbols is undefined (this is probably one
of the most commonly abused POSIX requirements; even the C++
standard flagrantly disregards it).

Martin