Hi all!

More and more people use LDC to cross-compile for other architectures. But end-to-end support is still missing. At least some basic tools and libraries differ: C compiler/assembler, linker, default druntime and phobos libraries.

Thinking about a solution, I came up with the following proposal. Currently, the config file is only used to define some command line switches. This can be extended to do a multi-level lookup for:

- definitions for tools (compiler, linker) and libraries (druntime, phobos)
- additional definitions for each target (command line switched, ...)

The lookup would sue the triple. The lookup order would be triple including environment, triple without environment, os only and default. The first entry matched is used. The config file would look like:

### Start of ldc2.conf
default:
{
    cc = gcc
    cctype = gnu
    ld = gcc
    ldtype = gnu
    switches = [ ... ]
    defaultlib = ...
    debuglib = ...
    linklibs = rt dl pthread m
}

*-*-freebsd:
{
    cc = clang
    linklibs = pthread m
}

*-*-win32:
{
    cc = cl
    cctype = ms
    ld = link
    ldtype = ms
    linkswitches = /NXCOMPAT /DYNAMICBASE
    linklibs = kernel32.lib user32.lib gdi32.lib
}

arm-*-linux-gnuehabi:
{
    cc = arm-unknown-linux-gnu-gcc
    ld = arm-unknown-linux-gnu-gcc
}

mips64-*-linux:
{
    cc = mips64-unknown-linux-gnu-gcc
    ld = mips64-unknown-linux-gnu-gcc
}
### End of ldc2.conf

E.g. compiling for Linux/MIPS64 (-mtriple=mips64-linux) would result in use of mips64-unknown-linux-gnu-gcc. Compiling for FreeBSD would use clang (because this is the default compiler in release 10). Default configuration is to use gcc for compiling/linking.

What do you think? Does this scheme cover the common cases encountered with cross compilation?

Regards,
Kai

Hi Kai,

On 5 May 2014, at 12:37, Kai Nacke via digitalmars-d-ldc wrote:
> More and more people use LDC to cross-compile for other architectures. But end-to-end support is still missing.

We are in desperate need of improvements on this front, I agree. I have been using various kludges to switch between environments and ldc2.conf files when cross-compiling myself too. And this in fact should be an area where LDC can really shine compared to e.g. GCC-based compilers, which basically require a whole separate install per target.

> The lookup would sue the triple. The lookup order would be triple including environment, triple without environment, os only and default. The first entry matched is used. The config file would look like:
> […]

This looks like a good start. Two ideas:
 - What format do you want to use for the config file? libconfig, like we are doing right now? (I didn't know what to make of the missing quotes in your example.)

 - Do more specific keys always completely override what a more general configuration group might contain? If yes, might there be situations where this gets cumbersome? The example I'm thinking about here is a possible future druntime version with different "ports" directories for the platform specific files, as has been discussed in the past. In this case, there might be an additional import path per platform, which should just be added to the other list of locations. (The question would be whether a facility to address this would be worth the added complexity, though…)

Another topic we need to address after this has been finalized is how to best integrate cross-compilation into the build process (this mainly concerns building druntime/Phobos).

Glad to see progress on this front!

Best,
David

Hi David!

On Tuesday, 6 May 2014 at 12:01:32 UTC, David Nadlinger via
digitalmars-d-ldc wrote:
> This looks like a good start. Two ideas:
>  - What format do you want to use for the config file? libconfig, like we are doing right now? (I didn't know what to make of the missing quotes in your example.)

I want to use libconfig as it provides the base features. However
I did not validate the syntax of my example file.

>  - Do more specific keys always completely override what a more general configuration group might contain? If yes, might there be situations where this gets cumbersome? The example I'm thinking about here is a possible future druntime version with different "ports" directories for the platform specific files, as has been discussed in the past. In this case, there might be an additional import path per platform, which should just be added to the other list of locations. (The question would be whether a facility to address this would be worth the added complexity, though…)

I thought about this, too. Some keys tend to be additive. The
switches key is a good example: if I want to add a switch to the
mips64 section (e.g. -mcpu=octeon) then it would be boring to
specify the path to the import modules again. But I dislike the
idea that not all keys work in the same way.

I solution would be specify to the behaviour in the config file
with = (final assigment) and += (add to less specific definition):

default:
{
     switches = [ "...", "..."]
}

mips64-*-linux:
{
     switches += [ "-mcpu=octeon" ]
}

As I don't know if this is possible with libconfig I would
postpone this to the D version of ldc.

> Another topic we need to address after this has been finalized is how to best integrate cross-compilation into the build process (this mainly concerns building druntime/Phobos).

Yes, that is a different topic which needs a solution....

> Glad to see progress on this front!

:-) I currently have too much targets to always fiddle around
with the config file.

Regards,
Kai

"Kai Nacke"  wrote in message news:qnuyfewnutwzozxlbxwk@forum.dlang.org... 

> [snip] the D version of ldc.

I like the sound of that!