Hi, I'm trying to integrate LDC into SlimD
(https://github.com/CyberShadow/SlimD).

1. I couldn't find an equivalent to DMD's -betterC, to avoid generating ModuleInfos. I thought that -fdata-sections and -ffunction-sections would make it unnecessary, however LDC still generates a .ctors section, which linkers don't discard.

2. How does one do incremental compilation and LTO with LDC? Clang has -emit-llvm, but ldc2.exe doesn't have such an option.

3. Do I understand correctly that LDC uses COFF object files, however uses gcc/ld for linking? Meaning that MinGW uses COFF files on Windows as well?

On 19 Sep 2014, at 6:45, Vladimir Panteleev via digitalmars-d-ldc wrote:
> 1. I couldn't find an equivalent to DMD's -betterC, to avoid generating ModuleInfos. I thought that -fdata-sections and -ffunction-sections would make it unnecessary, however LDC still generates a .ctors section, which linkers don't discard.

We are currently lacking something like that, unfortunately. It definitely would be worth adding something along the lines of -betterC (with a more descriptive name, that is).

There is pragma(LDC_no_moduleinfo) [1], though, which might still get you a long ways.

> 2. How does one do incremental compilation and LTO with LDC? Clang has -emit-llvm, but ldc2.exe doesn't have such an option.

-output-ll/-output-bc. You currently need to do the LTO part by hand, though (using opt and then llc to generate code).

> 3. Do I understand correctly that LDC uses COFF object files, however uses gcc/ld for linking? Meaning that MinGW uses COFF files on Windows as well?

OTOH, yes, MinGW also emits object files as COFF. If you are only interested in Win64 you could also try to use the MSVC-based toolchain. There are still some issues with it, but if you only need low-level stuff anyway and thus do not care about bugs in e.g. exception handling, it might work out just fine. Stripping unused sections actually works with link.exe, in contrast to MinGW's COFF linker.

David


[1] http://wiki.dlang.org/LDC-specific_language_changes#LDC_no_moduleinfo

On Friday, 19 September 2014 at 08:07:51 UTC, David Nadlinger via digitalmars-d-ldc wrote:
> There is pragma(LDC_no_moduleinfo) [1], though, which might still get you a long ways.

It did, thanks.

>> 3. Do I understand correctly that LDC uses COFF object files, however uses gcc/ld for linking? Meaning that MinGW uses COFF files on Windows as well?
>
> OTOH, yes, MinGW also emits object files as COFF. If you are only interested in Win64 you could also try to use the MSVC-based toolchain.

The MS linker seemed to work OK for my very simple cases.

> Stripping unused sections actually works with link.exe, in contrast to MinGW's COFF linker.

For some reason the MS linker left the .ctors section as-is in the resulting EXE, but pragma(LDC_no_moduleinfo) took care of that.