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Binary Size Optimization guidance for Fortress Rollback. Use when Reducing binary size, WASM size optimization, LTO configuration.
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Crate Publishing guidance for Fortress Rollback. Use when Publishing to crates.io, version bumps, release checklist.
Changelog Practices guidance for Fortress Rollback. Use when Writing CHANGELOG entries, deciding what to document.
Design Decision Log Pattern guidance for Fortress Rollback. Use when Architectural decisions, design alternatives, superseding prior choices.
Repository-wide engineering policy and project context for Fortress Rollback. Use when implementing, diagnosing, reviewing, testing, documenting, or releasing changes in this repository.
GitHub Actions Best Practices guidance for Fortress Rollback. Use when Writing GitHub Actions workflows, CI debugging, actionlint, caching.
Workspace Organization guidance for Fortress Rollback. Use when Organizing workspace, splitting crates, module structure decisions.
| name | binary-size |
| description | Binary Size Optimization guidance for Fortress Rollback. Use when Reducing binary size, WASM size optimization, LTO configuration. |
[profile.release]
opt-level = "z" # Optimize for size (try "s" too -- sometimes smaller)
lto = true # Link-time optimization
codegen-units = 1 # Better optimization
panic = "abort" # Remove unwinding machinery
strip = true # Strip symbols
RUSTFLAGS="-Zlocation-detail=none -Zfmt-debug=none" cargo +nightly build \
-Z build-std=std,panic_abort \
-Z build-std-features="optimize_for_size" \
--target x86_64-unknown-linux-gnu --release
| Technique | Rust | Impact | Behavior Change |
|---|---|---|---|
| Release build | 1.0+ | 60-70% | No |
strip = true | 1.59+ | 50-80% | No |
opt-level = "z" or "s" | 1.28+ | 10-30% | No |
lto = true ("fat") | 1.0+ | 10-20% | No |
codegen-units = 1 | 1.0+ | 5-15% | No |
panic = "abort" | 1.10+ | 10-20% | Yes: no unwinding |
-Zlocation-detail=none | Nightly | 5-15% | No panic location |
-Zfmt-debug=none | Nightly | 5-15% | No {:?} output |
-Z build-std | Nightly | 20-50% | No |
-Cpanic=immediate-abort | Nightly | 10-30% | No panic message |
| UPX compression | Post | 50-70% | AV flags, startup |
#![no_std] | 1.30+ | ~10KB possible | Limited API |
Always try BOTH "s" and "z" -- depending on code, "s" can be smaller.
| Category | Heavy | Lighter Alternative |
|---|---|---|
| CLI parsing | clap | lexopt, pico-args, argh |
| Serialization | serde | miniserde, nanoserde |
| HTTP | reqwest | ureq, minreq |
| Async runtime | tokio | smol, embassy |
| Regex | regex | regex-lite, memchr |
| Error handling | anyhow | thiserror only |
serde = { version = "1.0", default-features = false, features = ["derive"] }
tokio = { version = "1.0", features = ["rt", "net"] } # Not "full"
cargo bloat --release --crates # Size by crate
cargo bloat --release -n 30 # Top 30 functions
cargo llvm-lines --release | head -20 # Generic bloat
# WASM
twiggy top -n 20 target/wasm32-unknown-unknown/release/my_lib.wasm
[profile.release]
opt-level = "z"
lto = true
codegen-units = 1
panic = "abort"
strip = true
cargo build --release --target wasm32-unknown-unknown
wasm-opt -Oz -o optimized.wasm target/wasm32-unknown-unknown/release/my_lib.wasm
MSVC produces significantly smaller binaries (~10MB vs ~100MB for GNU/MinGW). Prefer MSVC for releases.
| Target | Trade-off |
|---|---|
*-linux-gnu | Smaller binary, needs glibc at runtime |
*-linux-musl | Larger binary, fully portable static |
FROM rust:1.83-alpine AS builder
RUN apk add --no-cache musl-dev
WORKDIR /app
COPY . .
RUN cargo build --release --target x86_64-unknown-linux-musl && \
strip target/x86_64-unknown-linux-musl/release/myapp
FROM scratch
COPY --from=builder /app/target/x86_64-unknown-linux-musl/release/myapp /myapp
ENTRYPOINT ["/myapp"]
| Base Image | Size |
|---|---|
debian:bookworm | ~130 MB |
alpine:3 | ~7 MB |
distroless/static | ~2 MB |
scratch | 0 MB |
--releasestrip = trueopt-level = "z" and "s"lto = truecodegen-units = 1panic = "abort" (if unwinding not needed)-Zlocation-detail=none-Zfmt-debug=none-Z build-std=std,panic_abort-Z build-std-features="optimize_for_size"cargo bloat --crates to audit heavy depscargo unused-features analyze| Step | Size | Reduction |
|---|---|---|
| Debug build | 4.2 MB | -- |
| Release | 410 KB | 90% |
| + strip | 310 KB | 93% |
| + opt-level=z | 290 KB | 93% |
| + LTO | 250 KB | 94% |
| + codegen-units=1 | 240 KB | 94% |
| + panic=abort | 180 KB | 96% |
| + build-std (nightly) | 51 KB | 99% |
| + UPX | 24 KB | 99.4% |
| Tool | Purpose |
|---|---|
cargo-bloat | Find what takes space |
cargo-llvm-lines | Find generic bloat |
cargo-unused-features | Find unused features |
twiggy | WASM code size profiler |
wasm-opt | WASM binary optimizer |
| UPX | Executable packer |