# Build Profiles

Load this reference when setting up or tuning a Rust project's Cargo build profiles. Tune profiles for the shape of the binary — defaults ship fast debug builds and modest-optimization release builds, but application Rust benefits from more aggressive profiles.

## Profile definitions (Cargo.toml)

```toml
# Production release: maximum optimization, minimum binary
[profile.release]
lto = "fat"           # Link-time optimization across all crates
codegen-units = 1     # Single codegen unit trades compile time for runtime perf
strip = true          # Strip symbols from the final binary
panic = "abort"       # No unwinding tables — smaller binary, faster panics

# Release with symbols kept for profiling (perf, flamegraph, pprof)
[profile.release-dbg]
inherits = "release"
strip = false
debug = true

# Size-minimized release for distributable CLIs
[profile.release-min]
inherits = "release"
opt-level = "z"       # Optimize for size over speed
```

`panic = "abort"` breaks `catch_unwind`-based recovery — skip it for libraries others will link against, or for binaries that rely on panic hooks (some web frameworks do). For most CLIs and backend services, it's pure win.

## Dev-machine compile speedups (.cargo/config.toml)

Cut PR compile time on Linux with mold:

```toml
[build]
rustflags = ["-C", "link-arg=-fuse-ld=mold"]

[target.x86_64-unknown-linux-gnu]
rustflags = [
    "-C", "link-arg=-fuse-ld=mold",
    "-C", "target-cpu=native",   # dev machines only — bakes in CPU features
    "-Z", "share-generics=y",    # share monomorphizations across crates (nightly)
]

[alias]
t = "nextest run"
```

Mold is Linux-only (`lld` on other platforms). `target-cpu=native` is a developer-machine convenience — remove for reproducible CI and distributable binaries.