library-development

name	library-development
description	Guide for creating and modifying Nanvix libraries under src/libs, including guest no_std and host std crates. Use this when asked about library architecture or crate changes.

Library Development

Use this skill when the user asks about developing, modifying, or adding system libraries in Nanvix. All libraries live under src/libs/ and are part of the Cargo workspace.

Library Categories

Core Libraries (Guest — #![no_std])

These run inside the Nanvix guest (user-space) and are compiled with cargo:

Library	Path	Purpose
arch	src/libs/arch/	Arch abstractions.
config	src/libs/config/	Config constants.
error	src/libs/error/	Error types.
sys	src/libs/sys/	System types.
syscall	src/libs/syscall/	Syscall interface.
sysapi	src/libs/sysapi/	System API.
sysalloc	src/libs/sysalloc/	Guest allocator.
syslog	src/libs/syslog/	Guest logging.
syslog-macros	src/libs/syslog-macros/	Log macros.
nvx	src/libs/nvx/	High-level API.
posix	src/libs/posix/	POSIX layer.
proc	src/libs/proc/	Process types.
type-safe	src/libs/type-safe/	Type-safe values.

Utility Libraries (Guest — #![no_std])

Library	Path	Purpose
bitmap	src/libs/bitmap/	Bitmap.
slab	src/libs/slab/	Slab allocator.
raw-array	src/libs/raw-array/	Fixed arrays.
static_assert	src/libs/static_assert/	Compile checks.
elf	src/libs/elf/	ELF parser.
libc_stdlib	src/libs/libc_stdlib/	C stdlib.
libc_string	src/libs/libc_string/	C strings.
no_fail	src/libs/no_fail/	No-fail alloc.

Host Libraries (Host — std available)

These run on the host system and are compiled with the host Rust build command (HOST_CARGO_BUILD_CMD, currently cargo):

Library	Path	Purpose
nanvix	src/libs/nanvix/	Host API.
nanvix-http	src/libs/nanvix-http/	HTTP.
nanvix-terminal	src/libs/nanvix-terminal/	Terminal.
hwloc	src/libs/hwloc/	HW topology.
profiler	src/libs/profiler/	Profiling.
syscomm	src/libs/syscomm/	Sockets.
user-vm-api	src/libs/user-vm-api/	User VM API.

Build Utilities

Library	Path	Purpose
build-utils	src/libs/build-utils/	Build helpers.

Creating a New Library

1. Create the directory under src/libs/<name>/.

2. Add a Cargo.toml with workspace package metadata:

   [package]
   name = "<name>"
   version.workspace = true
   license-file.workspace = true
   authors.workspace = true
   edition.workspace = true
   
   [dependencies]
   # Add dependencies here.
   
   [features]
   default = []
   std = []
   

3. Add the crate to the workspace members list in the root Cargo.toml.

4. Add the crate to the workspace [workspace.dependencies] section.

5. Add the library name to the appropriate list in the Makefile:

   • Guest: ALL_GUEST_RUST_LIBS (and optionally ALL_GUEST_RUST_LIBS_TEST_LIST).
   • Host: ALL_HOST_RUST_LIBS.

6. Add the copyright header to all source files.

7. Create src/lib.rs with proper module organization (see coding standards).

Building Libraries

# Build all guest libraries.
./z build -- all

# Run unit tests for host libraries.
./z build -- run-unit-tests

Guest libraries use GUEST_CARGO_BUILD_CMD (cross-compiled with cargo). Host libraries use HOST_CARGO_BUILD_CMD.

Windows Compilation

On a Windows development host, guest libraries are cross-compiled using a local toolchain, so they work identically to Linux. Host libraries that use std may need conditional compilation (#[cfg(target_os = "...")]) for platform-specific code paths (e.g., KVM, libc).

Note: Windows CI jobs run as part of the main CI pipeline. Platform-independent crates should still be manually verified on a Windows host when making changes that may affect cross-platform compatibility or Windows-specific behavior.

Coding Rules (Library-Specific)

• Guest libraries must support #![no_std] with optional std feature gate.
• Use default-features = false in workspace dependency declarations.
• Use c_size_t, c_ssize_t, c_int, etc. for C interoperability.
• Keep struct fields private; provide getter/setter methods.
• All public items must have doc comments with # Description, # Parameters, # Returns, and # Errors sections as applicable.
• Unit tests go in #[cfg(test)] modules; expect() is preferred over unwrap().