3 days ago

Posted by Dan

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Dan

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Hi Dlang forums.

I ran into some problems when trying to cross compile. Hope this clarifies the set-up for anyone with the same problems.

Additionally, perhaps these more explicit instructions / pitfalls could be put into the official wiki page about cross compiling. As a new user, this would have helped greatly.

Guide

Step 1: Obtain an LDC distribution compiled for the target

Prebuilt LDC binaries are found on the LDC GitHub repo's releases page

For a 64-bit windows target, download ldc2-<version>-windows-x64.7z. (note that you may need to click "see all releases", as some may be hidden by default).

Extract this archive.

Find the "lib" folder in the archive, then rename and move it to a system-wide location. The wiki page recommends %%ldcbinarypath%%/../lib-win64, which on my system is equivalent to /usr/lib-win64

Step 2: Tweak the LDC Configuration file

As per Cross Compiling with LDC, add your target "triple" name to the ldc2.conf file, putting the path to your target's "lib file" (the one that we extracted and moved in step 1) inside lib-dirs = [ ... ].

From my personal testing, lib-dirs allows absolute and relative paths.

Pitfall 1: Using the "wrong" LDC configuration file

Before tweaking the system-wide configuration in /etc/ldc2.conf, I wanted to test one out in the current working directory of my project, which according to Using LDC, is one of valid places that LDC will find a configuration file. I incorrectly assumed, however, that ldc2 will read both the local and system-wide config files.

So, I copied the the "Win64" configuration snippet from Cross Compiling with LDC into a local ldc2.conf (into my project's root), and ran ldc2 -mtriple=x86_64-windows-msvc source/app.d, but received an error

Error: `object` not found. object.d may be incorrectly installed or corrupt.
       ldc2 might not be correctly installed.
       Please check your ldc2.conf configuration file.
       Installation instructions can be found at http://wiki.dlang.org/LDC.

This happens because unlike our local configuration file, the system wide one (at /etc/ldc2.conf) contains a line that tells ldc2 where to find necessary files.

default:
{
    // ...
    post-switches = [
        "-I/usr/include/dlang/ldc",
    ];
    // ...
}

Solution 1: Use the system-wide ldc2.conf only

Copy your configuration to the system-wide /etc/ldc2.conf, then delete the ldc2.conf inside the poject directory

Solution 2: Add post-switches to the local config

Add the following lines to your local ldc2.conf, under switches. replace -I/usr/include/dlang/ldc with a different ldc includes path if necessary.

    post-switches = [
        "-I/usr/include/dlang/ldc",
    ];

Pitfall 2: Incorrect "lib-dirs" option

If you left your lib-dirs path as "%%ldcbinarypath%%/../lib-aarch64", it may be incorrect.

This value must reflect the location of the "lib" folder that we extracted and moved in step 1.

Step 3: Verify cross compilation is working

Compile a Dlang file for your target using ldc2. In my case, the command was ldc2 -mtriple=x86_64-windows-msvc source/app.d

If everything is set up correctly, congratulations! We now know how to cross compile with Dlang.

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