mirror of https://github.com/signalapp/libsignal.git synced 2024-09-20 03:52:17 +02:00

Jordan Rose 9c02d7a8cd Pods: Change the podspec to download prebuilds

Rather than building the Rust parts of libsignal as part of `pod
install`, fetch them from build-artifacts.signal.org. This requires
adding

    ENV['LIBSIGNAL_FFI_PREBUILD_CHECKSUM'] = '...'

to the consuming Podfile. The referenced archives are downloaded to
~/Library/Caches/org.signal.libsignal, and are unarchived as part of
the build. (The archives are outside the build directory so that a
clean build does not require a new download.)

Building with LibSignalClient as a local pod is still supported; in
that case everything will refer to the local target/ directory
instead. Use swift/build_ffi.sh to build as usual.

2023-01-12 16:47:28 -08:00

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Overview

This is a binding to the Signal client code in rust/, implemented on top of the C FFI produced by rust/bridge/ffi/. It's set up as a CocoaPod for integration into the Signal iOS client and as a Swift Package for local development.

Use as CocoaPod

Make sure you are using use_frameworks! in your Podfile. LibSignalClient is a Swift pod and as such cannot be compiled as a plain library.

Add 'LibSignalClient' and 'SignalCoreKit' as dependencies in your Podfile, as well as the prebuild checksum for the latest release. You can find this in Signal-iOS's Podfile.

 pod 'LibSignalClient', git: 'https://github.com/signalapp/libsignal.git'
 pod 'SignalCoreKit', git: 'https://github.com/signalapp/SignalCoreKit.git'
 ENV['LIBSIGNAL_FFI_PREBUILD_CHECKSUM'] = '...'

Use pod install or pod update to build the Rust library for all targets. You may be prompted to install Rust dependencies (cbindgen, rust-src).
Build as usual. The Rust library will automatically be linked into the built LibSignalClient.framework.

Development as a CocoaPod

Instead of a git-based dependency, use a path-based dependency to treat LibSignalClient as a development pod. Since prepare_commands are not run for path-based dependencies, you will need to build the Rust library yourself. (Xcode should prompt you to do this if you forget.)

CARGO_BUILD_TARGET=x86_64-apple-ios swift/build_ffi.sh --release

The CocoaPod is configured to use the release build of the Rust library.

If validating LibSignalClient locally, use the following invocation:

pod lib lint \
  --platforms=ios \
  --include-podspecs=../SignalCoreKit/SignalCoreKit.podspec \
  --skip-import-validation \
  --verbose

You will also need to have SignalCoreKit checked out; the above command assumes you have checked it out as a sibling directory to libsignal.

When exposing new APIs to Swift, you will need to add the --generate-ffi flag to your build_ffi.sh invocation.

Development as a Swift Package

Build the Rust library using swift/build_ffi.sh. The Swift Package.swift is configured to use the debug build of the Rust library.
Use swift build and swift test as usual from within the swift/ directory.

When exposing new APIs to Swift, you will need to add the --generate-ffi flag to your build_ffi.sh invocation.

Use as a Swift Package

...is not supported. In theory we could make this work through the use of a custom pkg-config file and requiring clients to set PKG_CONFIG_PATH (or install the Rust build products), but since Signal itself does not use this configuration it's considered extra maintenance burden. Development as a package is supported as a lightweight convenience (as well as a cross-platform one), but the CocoaPods build is considered the canonical one.

Catalyst Support

Rust targets for Mac Catalyst are still in tier 3 support, so we use the experimental -Zbuild-std flag to build the standard library.

In order to compile for these platforms you will need to:

Install the standard library component with rustup component add rust-src
If not using Cocoapods, add the --build-std flag to your build_ffi.sh invocation

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