Recommended way of adding additional libraries to link against

[shaunmulligan]

@japaric thanks for this awesome project!!
I was just wondering how some one should go about adding additional libraries that need to be linked against. Some projects like https://github.com/plietar/librespot require additional dependencies such as portaudio19-dev and maybe some others. I was just wondering what is the appropriate method for adding these into cross so that the project builds correctly.

[japaric]

Simplest way: build the library as a static library in a build script and link to that.

If you want to link to a shared library and you are using the pkg-config crate, then you basically can't cross compile because that crate doesn't support cross compilation scenarios (AFAIK).

If you want to link to a cross compiled shared library provided by ubuntu, e.g. libfoo-dev:i386, or against a shared library that you intent to build manually, you'll have to override the docker and the only way to do that is to create a local image named, for example, japaric/i686-unknown-linux-gnu:v0.1.3 because that's what cross expects it to be called.

I suggest you base that local image on the ones cross uses by default. So you could use something like this for the Dockerfile:

FROM japaric/i686-unknown-linux-gnu:v0.1.3

# Or build it yourself
RUN dpkg --add-architecture i386 && \
    apt-get update && \
    apt-get install --no-install-recommends -y libfoo-dev:i386

[iav]

This method, and code from main page, not work.
Because Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/universe/binary-armhf/Packages, same for

FROM rustembedded/cross:aarch64-unknown-linux-gnu-0.1.16

RUN dpkg --add-architecture arm64 && \
    apt-get update && \
    apt-get install libfoo:arm64

Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/main/binary-arm64/Packages 404 Not Found
Because trusty have only amd64 and i386 architectures in repos.

[gdesmott]

I'd suggest to close this as a dup of #149 as that's basically the same issue and this ticket contains extra information about how to make this work.

[rvolgers]

If I understand correctly, this is precisely what was fixed in 3b07a08

[Alexhuszagh]

We've documented this now extensively on the wiki, including the following examples:

• Using Debian Repositories
• Linking External Libraries

We've also included complete projects using examples both with pre-build hooks and custom Docker images for this purpose.

• dbus
• openssl-certs

We've also made it a lot simpler, since we've added CROSS_DEB_ARCH when using pre-build hooks, so the following can be done:

[build]
pre-build = [
    "dpkg --add-architecture $CROSS_DEB_ARCH",
    "apt-get update && apt-get install --assume-yes libssl-dev:$CROSS_DEB_ARCH"
]

So this code could will actually work for nearly every target (at least those targeting Linux GNU targets with architectures supported by Debian repositories), making this quite a versatile approach.