When I try build my application using LDC and -flto=thin it fails in the final linking as

ldmd2 -of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2B7F/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2B7F/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-0CE08DAF93E48445402E07C3537FA4E6/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-933571CC843E8D13926CEC14051E7195/libknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz -L-lbz2
/usr/bin/ld: error: .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2B7F/knetquery.o:1:3: invalid character
/usr/bin/ld: error: .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2B7F/knetquery.o:1:3: syntax error, unexpected $end
/usr/bin/ld: error: .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2B7F/knetquery.o: not an object or archive
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o:function _start: error: undefined reference to 'main'
collect2: error: ld returned 1 exit status
Error: /usr/bin/gcc failed with status: 1
FAIL .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2B7F/ knetquery executable
ldmd2 failed with exit code 1.

What could be wrong?

On Monday, 26 March 2018 at 22:07:49 UTC, Nordlöw wrote:
> When I try build my application using LDC and -flto=thin it fails in the final linking

You must also pass `-flto=thin` during linking (a special plugin is needed for LTO, and LDC will only pass the plugin to the linker when `-flto=` is specified).
I couldn't see `-flto=thin` in your link command, so I suspect that will fix it.

- Johan

On Monday, 26 March 2018 at 22:13:02 UTC, Johan Engelen wrote:
> On Monday, 26 March 2018 at 22:07:49 UTC, Nordlöw wrote:
>> When I try build my application using LDC and -flto=thin it fails in the final linking
>
> You must also pass `-flto=thin` during linking (a special plugin is needed for LTO, and LDC will only pass the plugin to the linker when `-flto=` is specified).
> I couldn't see `-flto=thin` in your link command, so I suspect that will fix it.
>
> - Johan

I added `lflags` to my dub configuration as

buildType "release-nobounds-lto" {
         buildOptions "releaseMode" "optimize" "inline" "noBoundsCheck" # TODO -march=native -ffast-math
         dflags "-mcpu=native" "-O3" "-flto=thin" platform="posix-ldc"
         lflags "-flto=thin" platform="posix-ldc"
}

forwarded as `-L-flto=thin` but still errors as

Linking...
ldmd2 -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-flto=thin -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz -L-lbz2
/usr/bin/ld: error: .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B23442E/knetquery.o:1:3: invalid character
/usr/bin/ld: error: .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B23442E/knetquery.o:1:3: syntax error, unexpected $end
/usr/bin/ld: error: .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B23442E/knetquery.o: not an object or archive
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o:function _start: error: undefined reference to 'main'
collect2: error: ld returned 1 exit status
Error: /usr/bin/gcc failed with status: 1
FAIL .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B23442E/ knetquery executable
ldmd2 failed with exit code 1.

On Monday, 26 March 2018 at 22:07:49 UTC, Nordlöw wrote:
> When I try build my application using LDC and -flto=thin it fails in the final linking as
>

According to LDC's Release info:

Known issues:
ThinLTO may not work well with the ld.bfd linker, use ld.gold instead (-linker=gold).


Maybe this is the problem.

Arek

On Monday, 26 March 2018 at 23:32:59 UTC, Nordlöw wrote:
> forwarded as `-L-flto=thin` but still errors as

Which is wrong, it's not a ld command-line option (i.e., the `-L` prefix is wrong). I don't use dub though, so I don't know how to fix it.

On Tuesday, 27 March 2018 at 13:28:08 UTC, kinke wrote:
> On Monday, 26 March 2018 at 23:32:59 UTC, Nordlöw wrote:
>> forwarded as `-L-flto=thin` but still errors as
>
> Which is wrong, it's not a ld command-line option (i.e., the `-L` prefix is wrong).

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

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!

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!

Good :-)

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.

There will be similar problems with using ASan (and fuzzer aswell):  `-fsanitize=address` must also be passed to the D compiler (not the linker) during linking such that the correct asan library is linked into the executable.

- Johan

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!
>
> Good :-)
>
> 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.
>
> There will be similar problems with using ASan (and fuzzer aswell):  `-fsanitize=address` must also be passed to the D compiler (not the linker) during linking such that the correct asan library is linked into the executable.
>
> - Johan

dub supports dflags and lflags in the config file. lflags are the linker commands.

http://code.dlang.org/package-format?lang=sdl#build-settings

You can also specify per platform arguments, e.g.

dflags "-version=BuildingWithLDCRocks" platform="ldc"

(dub even supports the environment variables DFLAGS which dmd doesn't (and of course LFLAGS))

On Wednesday, 28 March 2018 at 17:03:07 UTC, Seb wrote:
> 
> dub supports dflags and lflags in the config file. lflags are the linker commands.

Please read the thread.

`lflags` is for passing flags to the _linker_ (i.e. those flags are prefixed with -L when passed to the _compiler_)

Here, what's needed is passing flags to the _compiler_ when it is invoked to perform the link step in the build.

-Johan