Feature Flags

SteelMC uses Rust feature flags to enable or disable functionality at compile time. Use them to tailor a build for production, debugging, profiling, telemetry, or generated-code maintenance.

Most users build the server binary through the steel package:

cargo build -p steel --features "feature_name"

steel

These flags control the main server executable.

Feature	Default	Description
mimalloc	Yes	Uses MiMalloc as the global allocator for improved allocation performance.
stand-alone	No	Embeds the default favicon and writes it when the configured favicon file is missing.
deadlock_detection	No	Enables parking_lot deadlock detection for debugging.
dhat-heap	No	Enables the DHAT heap profiler for memory analysis. This replaces MiMalloc as the global allocator when both are enabled.
spawn_chunk_display	No	Shows a colored terminal grid while startup spawn chunks are generated.
slow_chunk_gen	No	Slows chunk generation during spawn preparation and forwards steel-core/slow_chunk_gen; useful for observing the spawn chunk display.
jaeger	No	Enables OpenTelemetry tracing export through OTLP for Jaeger-compatible tracing setups.

Usage Examples

# Build with deadlock detection
cargo build -p steel --features deadlock_detection

# Build without the default MiMalloc allocator
cargo build -p steel --no-default-features

# Build with the spawn chunk display
cargo build -p steel --features "spawn_chunk_display slow_chunk_gen"

# Build with Jaeger/OpenTelemetry tracing support
cargo build -p steel --features jaeger

steel-core

These flags control core game logic and lower-level debugging helpers.

Feature	Default	Description
stand-alone	No	Defined in the crate manifest, but currently has no active cfg(feature = "stand-alone") code paths in steel-core. The server binary’s stand-alone feature handles the embedded favicon behavior.
slow_chunk_gen	No	Adds a short delay after chunk generation stages when the server enables slow spawn generation.
flint	No	Exposes behavior introspection helpers, including concrete behavior type names and behavior registry slices.

steel-registry

These flags control the game registry system and generated registry code.

Feature	Default	Description
fmt	No	Runs rustfmt over generated registry files during the build script.
minecraft-src	No	Enables helpers that compare generated registry data against the generated minecraft-src reference data.

steel-utils

These flags control generated utility data.

Feature	Default	Description
fmt	No	Runs rustfmt over generated utility files during the build script.

steel-worldgen

These flags control generated world-generation data.

Feature	Default	Description
fmt	No	Runs rustfmt over generated world-generation files during the build script.

Combining Features

You can enable multiple features in one build:

# Build with several server debugging features
cargo build -p steel --features "deadlock_detection spawn_chunk_display slow_chunk_gen"

# Build for a standalone-style server distribution
cargo build -p steel --release --features stand-alone

# Format generated registry output while building that crate
cargo build -p steel-registry --features fmt

Feature flags are package-scoped. When enabling features outside the steel package, pass the target package explicitly with -p.

Production Recommendations

For production servers, prefer:

• Keep mimalloc enabled unless you are profiling with dhat-heap.
• Keep deadlock_detection, dhat-heap, spawn_chunk_display, and slow_chunk_gen disabled.
• Enable stand-alone only when you want the server binary to provide the default favicon file.
• Enable jaeger only when you have an OTLP tracing collector configured.
• Use fmt and minecraft-src for development and generated-code validation, not normal production builds.