version: multiple conditions

[Joakim via Digitalmars-d]

On Saturday, 13 June 2015 at 21:51:43 UTC, bitwise wrote:
> On Sat, 13 Jun 2015 17:29:17 -0400, Xiaoxi <xiaoxi at 163.com> 
> wrote:
>
>> On Saturday, 13 June 2015 at 21:19:28 UTC, bitwise wrote:
>>> On Sat, 13 Jun 2015 17:16:04 -0400, weaselcat 
>>> <weaselcat at gmail.com> wrote:>
>>>> iirc this falls under the "walter dislikes it so we won't 
>>>> have it" category.
>>>
>>> As Andrei said at DConf though, consensus requires at least 3 
>>> people ;)
>>>
>>>  Bit
>>
>> The current design encourages using more finegrained features 
>> instead of the more blunt Os level versions.
>>
>> version(iOS) { version = pthread;}
>> version(Android) { version = pthread;}
>>
>> In the rest of the file simply check for pthread instead of OS.
>
>
> That _sounds_ nice, but consider this:
>
> version (linux) {
>     import core.sys.linux.dlfcn;

version = use_dlopen;

> }
> else version (FreeBSD) {
>     import core.sys.freebsd.dlfcn;

version = use_dlopen;

> }
>
> version(linux || FreeBSD) {

   //version(linux || FreeBSD) {
     version(use_dlopen) {

>     dlopen(...)
> }
>
> I shouldn't have to add another version just for that last 
> dlopen block. It's not "finegrained" control, it's cruft.

It does require more definitions, but it's worth it.  A simple 
example like yours may seem excusable, but there's no way to 
limit such logic to just simple instances.  Walter is coming from 
long experience with this, and even with my limited experience 
with such logic, I'm grateful for it, as dealing with more 
complex versions of such logic is a royal PITA.