Build and Run

This chapter introduces the build commands used in regular project development.

Build a Project

feng build
feng build --release

You can pass either a project directory or a feng.fm path:

feng build ./examples/hello_world
feng build ./examples/hello_world/feng.fm

Debug builds retain information useful for debugging. --release enables release build mode.

Run a Project

feng run
feng run --release
feng run -- argument-one argument-two

run runs only a target: "bin" project for the current host platform. Library projects cannot be run directly.

Target Platforms

If feng.fm does not declare platform, running build without platform options builds for the host platform. You can select platforms explicitly:

feng build --platform=macos-arm64
feng build --platform=linux-x64-gnu
feng build --platform=linux-arm64-musl

You may pass --platform more than once. If the manifest declares a platform list, that list serves as both the default target set and the set of allowed targets.

A Linux platform name must include gnu or musl. A valid target identifier does not guarantee that the current installation contains the required toolchain or SDK.

Custom Sysroot

A single-platform build can specify a sysroot explicitly:

feng build --platform=linux-x64-musl --sysroot=/opt/sysroots/musl-x64

When --sysroot is specified, only one platform can be built at a time. Feng does not download, copy, or license third-party SDKs for you.

Package a Library

For a target: "lib" project, use:

feng pack
feng pack --platform=macos-arm64 --platform=linux-x64-gnu

pack always performs a release build and writes an .fb file to <out>/pkg/ after a successful build. Every requested platform must build successfully before the final package is created.

Clean

feng clean

This command removes all build artifacts associated with the current project manifest.

Compile Source Files Directly

Third-party build systems and advanced workflows can pass source files directly:

feng src/main.ff --target=bin --name=myapp --out=build

Direct compilation mode does not read feng.fm or resolve a dependency graph. Prefer build, run, and check for normal project development.