All functions COMDAT on OSX

[bitwise via Digitalmars-d]

On Monday, 16 November 2015 at 08:15:39 UTC, Walter Bright wrote:
> On 11/15/2015 8:44 PM, bitwise wrote:
>> https://issues.dlang.org/show_bug.cgi?id=15342
>>
>> DMD emits all functions as COMDAT on OSX.
>>
>> I'm guessing this was originally a workaround of some 
>> kind...does anybody know
>> the story?
>>
>> Thanks,
>>      Bit
>
> It enables:
>
> 1. the linker to remove duplicates (happens with templates and 
> other things)
> 2. the linker to remove unreferenced COMDATs

I understand what it's for, but it's incorrect behaviour to have 
_all_ functions being emitted as comdat. Non-template functions 
shouldn't be coalesced in this way. If you compile the code 
example in the bug report with *any* compiler other than DMD/OSX, 
the example will fail as described, with a linker error. The 
example compares dmd/osx with gcc/osx, but the code will also 
fail with ldc/osx. And although I don't have time to check, I'm 
pretty sure it will fail with dmd/win as well.

If you look at the code I cited, this is obviously a hack:

<glue.c#L866-L870>
[...]
#if TARGET_OSX
     s->Sclass = SCcomdat;
#else
     s->Sclass = SCglobal;
#endif
     for (Dsymbol *p = fd->parent; p; p = p->parent) {
         if (p->isTemplateInstance()) {
             s->Sclass = SCcomdat;
             break;
         }
     }
[...]

     Bit