Build Systems

Hylo currently supports incremental compilation at a module level granularity. We can either use the Hylo CLI (hc) to compile simple programs, or use CMake to orchestrate the whole build pipeline. Although we only implemented support for CMake, it should be possible to integrate with other build systems (contributions are welcome!).

If you just want to get started quickly, you can compile a single-module executable:

hc main.hylo fibonacci.hylo

CMake

The experimental CMake support is developed at https://github.com/tothambrus11/hylo-cmake-support/. You can use it as a starter project template.

There are a handful of limitations of CMake that currently prevent us from adding Hylo as a custom language to CMake while maintaining build correctness and efficiency, which are documented in the CMake Upstream Plan. In the meantime, we rely on custom commands, which get the job done.

Adding support to other build systems

Example: building an executable composed of two modules: App importing Foo:

# Compiling Foo:
hc --module-name Foo
    --emit object
    -o Foo.o
    --emit-module-to build/Foo.hylomodule
    --emit-module-interface-hash-to build/Foo.hash
    Sources/Foo

# Compiling App, importing Foo:
hc --module-name App
    --import Foo
    --module-search-path build
    --emit object
    -o App.o
    Sources/App

# Compile the parts of the standard library that contain linkable symbols:
clang -c "$(hc --print-stdlib-root)/shims.c" -o build/stdlib_shims.o

# Link everything:
cd build
clang App.o Foo.o stdlib_shims.o -o app

The module interface hash file of Foo is written to as specified by --emit-module-interface-hash-to. The dependant module App only needs to be recompiled if the interface hash of Foo is changed or if any of the source files in App are changed.

CLI flags:

• --module-name <name>: name of the module being compiled (defaults to the source file’s name if exactly one is given, or Main).
• --import <module>: make a module visible to the one being compiled. Each is loaded from <module>.hylomodule from the module search path.
• --module-search-path <path>: where to look for imported archives. This is now distinct from -L, which is only for native libraries.
• --emit-module-to <file>: write the compiled module’s archive so others can import it.
• --emit-module-interface-hash-to <file>: write a hash a build system can use as a rebuild key for dependents. The file is only rewritten when the hash changes, so tools looking at modififcation time work efficiently.
• --print-stdlib-root: print the standard library root and exit.

See others using hc --help.