Building application with LDC and -flto=thin fails in link stage

[Johan Engelen]

On Wednesday, 28 March 2018 at 16:42:23 UTC, Johan Engelen wrote:
> On Tuesday, 27 March 2018 at 22:10:33 UTC, Per Nordlöw wrote:
>> On Tuesday, 27 March 2018 at 22:00:42 UTC, Johan Engelen wrote:
>>> Indeed.
>>> Please try to manually link first (without dub) by modifying 
>>> the command on which dub errors:
>>>
>>> ```
>>> ldmd2 -flto=thin 
>>> -of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B23442E/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B23442E/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-B287F67CE5FF6145BC229790CFB09607/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F0F2FDB01B8401C04D657BCC145D46A5/libknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz -L-lbz2
>>> ```
>>>
>>> -Johan
>>
>> Yes, that works!
>
> I'm no dub expert and I don't know how to pass flags to the 
> _compiler_ for the link step.
> Would be good to figure that out with the dub folks.

For a stopgap solution:
I think what you are doing is passing 
`--compiler=<yourpath>/ldmd2` (note: LDMD) to dub when building, 
and you get separate compilation+linking. If you'd use 
`--compiler=<yourpath>/ldc2` (note: LDC), then you would not get 
separate compilation+linking [1] and things work with just 
setting `dflags`.

I've asked about the problem here: 
https://github.com/dlang/dub/issues/1431

cheers,
   Johan

[1] https://github.com/dlang/dub/issues/809