[challenge] Linker surgery

[Dmitry Olshansky]

18-May-2013 10:40, Rainer Schuetze пишет:
>
>
> On 18.05.2013 00:49, Dmitry Olshansky wrote:
>> 17-May-2013 21:57, Rainer Schuetze пишет:
>>>
>>>
>>> On 17.05.2013 14:29, Dmitry Olshansky wrote:
>>>> 15-May-2013 04:17, IgorStepanov пишет:
>>>>> Do this table linked, if you remove all functions, which use it?
>>>>
>>>> Thanks for this try, but they DO link in always.
>>>> And I believe this is a key problem - each function goes into a
>>>> separate
>>>> object but globals are always pulled in!
>>>>
>>>
>>> Yes, if you build a library the functions in a module are split into
>>> separate object files, but data is always written into the object file
>>> of the original module. The linker cannot split these afterwards if any
>>> data in the module is referenced (which might happen by just importing
>>> the module).
>>
>> And how then I would use these tables if even importing these modules
>> then pulls in the data?
>>
>
> It depends. An imported module is referenced if it is part of the
> dependency chain for static constructors, i.e if it contains static
> this() or imports something that contains it. A module with just data in
> it should be fine.
>
>
>> Local import doesn't help too.
>>
>>> A workaround could be to put the data into a different module.
>>
>> Then say I go for X files with tables and import these modules.
>> It still doesn't work - evidently simply referencing a module pulls in
>> the data.
>>
>> If I compile and link the following 3 modules:
>>
>>
>> module fmod;
>>
>> public immutable int[] fable = [1,2,3];
>>
>>
>> module mod;
>>
>> import fmod;
>>
>> int foo(int i)
>> {
>>         return fable[i];
>> }
>>
>> //driver
>> import mod;
>>
>> immutable byte[] bable = [1, 2, 3, 4, 5];
>>
>> byte boo(int ch){
>>      return bable[ch];
>> }
>>
>> void main(string[] args){
>>      boo(0);
>> }
>>
>> I still have this symbol in map file: _D4fmod5fableyAi
>> That is immutable(int[]) fmod.fable after ddemangle.
>>
>
> If you compile all the files on the command line for the executable
> everything gets dragged in.

Then the only question would be - why we need this behavior?
It looks painfully clear to me that -lib style should be the default.

 >You will have to build the first two modules
> into a library:
>
> dmd -lib fmod.d mod.d -ofm.lib
> dmd -map driver.d m.lib
> grep fmod driver.map
>
> Splitting functions into separate object files also only happens when
> -lib is specified.

Great then even this seems to work:

module mod;

int foo(int i)
{
     static immutable int[] fable = [1,2,3]; //table_.mangleof == "table_";
     return fable[i];
}

public void car(){

}

//driver
import mod;

immutable byte[] bable = [1, 2, 3, 4, 5];

byte boo(int ch){
     return bable[ch];
}

void main(string[] args){
     boo(0);
     car();
}

-- 
Dmitry Olshansky