Clang-build

[ Demonstration ]()

Find the full documentation at https://clang-build.readthedocs.io

Motivation:

Building as much as possible from source eases dependency management and ensures stability and reproducibility
Meta build systems are inherently the wrong way to go, either the build system or the compiler should be platform-agnostic (ideally both).
Trying to cover all use-cases is the wrong way to go - there is no need to let people do it the wrong way
CMake is cumbersome, unnecessarily generic and verbose and people should not need a programming/scripting language whose only purpose is to build C++
With Clang, finally a properly cross-platform compiler exists

Goals:

One compiler (Clang), one build system (written in Python)
Automatic integration with language servers (compile_commands.json)
Simple projects should be simple to build
Build process for reasonable project structures should still be easy
Adding third-party dependencies should be manageable

What it's not designed to do:

Build anything aside from C language dialects
Be able to adapt to any project structure in the world - certain standards are encouraged
Work smoothly with or locate pre-built libraries and libraries installed by system package managers

Related resources:

Usage

In order to run clang-build, you only need Clang and Python3. Install via pip install clang-build (add the --user flag if you don't have admin rights).

Running clang-build will try to build the current directory. The command-line options include

-d path/to/dir to build a different directory
-p to show a progress bar
-V to print some additional info
--debug to print the called clang commands

The given directory will be searched for a clang-build.toml file, which you can use to configure your build targets, if necessary. However, if you only want to build an executable, you will likely not even need a build file.

clang-build tries to use sane defaults, designed to make most projects very easy to configure and even complex projects far easier than with common build or meta-build systems.

Real-World Examples

Examples of real-world used and tested projects, which can be easily be integrated into your project using clang-build:

test/boost-filesystem

General Ideas

Note: not all of these are implemented, yet.

What should be trivial

This would be things that require only the invocation of clang-build and no build file.

build any hello world program or other MWE, given a reasonable folder structure (i.e anything with a main and without non-std dependencies)
include anything that can be found by sane default search
using command line arguments:
- specify root/source and build directories
- set build type (last used should be cached/remembered)
- set verbosity

Sane defaults and default behaviour:

platform-independence
build into a "build/" directory, not into toplevel
for multiple targets build each into its own "build/targetname"
default search paths for different platforms, including also e.g. "./include", "./lib", "./build/lib", "/usr/local/...", ...

What should be easy

This would be things that only require a minimal TOML project file

add dependency / external project from source folder or remote (e.g. github)
header-only should be trivial
for a library with a good folder structure, it should be easy to write a build config
create a library from one subfolder, an executable from another and link them
setting target-specific (note: defaults should be sane!)
- source file extensions
- source directories
- compile and link flags
- optional version
- dependencies (which may include non-targets, e.g. configuration steps)
- properties (required c++ version, definitions/#defines, ...)
access to flag "lists" such as flags for
- coverage
- cuda
- openmp
set target-specific flags, include folders, etc. which should not be propagated to dependency parents as "private"

What should be possible

Steps that would involve more effort from the user, including possibly some python code

a Target configuration step before building (e.g. for more involved version numbering)
through the configuration step, inclusion of e.g. CMake-project should be possible
packaging: any target may be packaged, meaning it's dependencies are handled and if built, binaries may be bundled
external package dependencies
binaries on a server
source on a server (fallback from binaries)
binaries on disk, try to determine version from path and file names
source on disk, try to determine version from path and file names

Project File By Example

A single target

Note:

by default, the root and <targetname> folders, as well as "include" and "src" subdirectories will be searched for ".hpp", ".hxx", ".h" and ".cpp", ".cxx" and ".c" files
a target without target_type, but with source files will be an executable
output_name should not contain pre- or suffixes such as lib, .exe, .so, as they are added automatically
if we don't care about the output name, in this case we could skip the project file entirely

# Top-level brackets indicate a target
[hello]
output_name = "runHello"

Two targets with linking

# Build a library
[mylib]
target_type = "shared library"

# Build an executable and link the library
[myexe]
output_name = "runExe"
target_type = "executable"
dependencies = ["mylib"]
[myexe.flags]
link = ["-DMYEXE_SOME_DEFINE"]

Adding external dependencies