Speed up Linux builds with Wild Linker 0.9—a Rust‑based linker with LTO plugin support and cleaner platform porting. Learn how to use it today.
The Linker: Your Build Pipeline’s Silent Bottleneck
You’ve optimized your compiler flags, parallelized your source compilation, and moved to a fast SSD. Yet your build still takes minutes—sometimes tens of minutes—to finish. Where’s the holdup? For many medium‑to‑large projects, the linker is the forgotten culprit.
Traditional linkers like GNU ld and even gold were designed in an era of smaller binaries and simpler memory layouts.
They struggle with today’s massive codebases, template‑heavy C++, and Rust’s rich monomorphization. Every time you change a single shared header, the linker may have to re‑examine and merge thousands of object files.
Enter Wild Linker—a from‑scratch implementation in Rust that focuses on raw speed, low memory overhead, and modern parallelism. Version 0.9 doesn’t scream “revolution”, but it quietly cements Wild as a reliable alternative for production Linux builds, while opening the door to non‑ELF platforms.
What You’ll Learn
- Why linkers become bottlenecks and how Wild’s architecture avoids common slowdowns.
- The practical impact of Wild 0.9’s platform‑refactoring and ELF‑specific isolation.
- How the newly supported GNU LD plugin API enables LTO and custom linker plugins.
- A step‑by‑step guide to trying Wild on your own project—without breaking your existing toolchain.
- Common mistakes when switching linkers (and how to avoid them).
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Understanding the Linker Bottleneck
Before diving into Wild, it helps to know why linking can be so slow in the first place.
What a Linker Actually Does
Symbol resolution – Matches every undefined symbol (e.g., printf, std::vector<int>::push_back) to its definition across many object files and libraries.
- Section merging – Combines code, data, read‑only, and debug sections from all inputs into a single output.
- Relocation – Adjusts addresses so that jumps and calls land in the right places.
- Optimization (optional) – Eliminates dead code, merges identical constants, and (with LTO) re‑optimizes across compilation units.
Traditional linkers process these steps sequentially, using data structures that don’t scale well. When you have 10,000 object files, a naïve O(n²) symbol lookup can turn into seconds or minutes of CPU time.
How Modern Linkers (Like Wild) Fix That
- Parallelism – Wild splits work across multiple threads where possible (e.g., parsing input files, computing section layouts).
- Efficient hash tables – Symbol lookups are O(1) average, not O(n) or O(log n) with large constant factors.
- Lazy loading – Wild reads only the necessary parts of each object file, not the whole thing upfront.
- Rust’s memory safety – Avoiding C++’s pointer aliasing issues and undefined behavior allows more aggressive optimisations.
Note: Wild is not the first fast linker—mold (also written in a systems language, but C++) pioneered many of these ideas. Wild offers an alternative implementation in Rust, which some teams prefer for its memory safety guarantees and ecosystem.
What Wild Linker 0.9 Brings to the Table
Version 0.9 is an infrastructure release. The headline features aren’t eye‑catching performance gains—they’re about future‑proofing.
1. Platform Abstraction & Porting Work
Earlier versions of Wild were tightly coupled to ELF (Executable and Linkable Format), the standard binary format on Linux. To support other operating systems and targets, the 0.9 release refactors the codebase:
- ELF‑specific logic (relocation types, section headers, symbol tables) is isolated behind well‑defined traits.
- Common linking logic (symbol resolution, archive handling, error reporting) is now platform‑agnostic.
- Draft implementations for Mach‑O (macOS/iOS) and WebAssembly are already in the codebase, though not yet functional.
Why this matters for you today
Even if you only target Linux, a cleaner internal architecture means fewer bugs, faster feature development, and better maintainability. It also signals that the Wild team is serious about supporting non‑Linux environments in the future—so your investment in learning Wild today may pay off across more platforms tomorrow.
2. GNU LD Plugin API Support
This is the most immediately useful feature for many projects. GNU ld and mold have supported a plugin API for years, used primarily for:
Link‑Time Optimization (LTO) – The compiler (e.g., GCC or Clang) emits LLVM bitcode instead of native object code. The linker plugin invokes the compiler backend at link time to perform whole‑program optimisations.
Custom link‑time transformations – e.g., symbol renaming, dead code elimination, or even generating metadata.
Wild 0.9 now implements the same plugin API, which means:
- Drop‑in compatibility with ar, gcc, clang, and rustc when they use -flto or -fuse-ld=wild.
- No need to change your LTO workflow—just point the compiler driver to Wild, and the plugin mechanism works transparently.
- Third‑party plugins written for GNU ld or mold should work without modification (as long as they only rely on the documented API).
Practical impact: If you already use LTO to reduce binary size or improve runtime performance, switching to Wild will not break that. And because Wild is often faster at the final link step, your LTO‑enabled builds will become noticeably quicker.
3. Refinements & Bug Fixes (No Major Performance Changes)
The 0.9 release notes mention “various other refinements” but explicitly state no major performance changes are expected. That’s perfectly fine for an evergreen perspective: performance was already excellent in 0.8.
The team has focused on correctness, portability, and API compatibility—all of which are more important for long‑term adoption than chasing another 2% speedup.
What this means for you – You can confidently use 0.9 as a stable baseline. Future versions will add performance enhancements on top of this solid foundation.
How to Get Started with Wild Linker
Let’s move from theory to practice. Wild is not yet packaged in most Linux distributions, but installation is straightforward.
Step 1: Install from GitHub Releases
Visit the Wild Linker GitHub repository (not linked directly—search for “wild linker” if needed). Download the pre‑built binary for your architecture (x86_64 or aarch64) or build from source using Cargo.
# Example: download and install release 0.9 wget https://github.com/davidlattimore/wild/releases/download/v0.9.0/wild-v0.9.0-x86_64-unknown-linux-gnu.tar.xz tar xf wild-v0.9.0-x86_64-unknown-linux-gnu.tar.xz sudo cp wild /usr/local/bin/
Building from source – If you prefer, cargo install --git
https://github.com/davidlattimore/wild wild will compile the latest version. This requires a Rust toolchain.
Step 2: Tell Your Compiler to Use Wild
The easiest method is to set the -fuse-ld flag:
GCC / Clang: gcc -fuse-ld=wild main.c -o main
Cargo (Rust): Create .cargo/config.toml with:
[target.x86_64-unknown-linux-gnu] linker = "clang" # or "gcc" rustflags = ["-C", "link-arg=-fuse-ld=wild"]
Alternatively, replace the system linker by moving /usr/bin/ld and symlinking wild to ld (not recommended for production). The -fuse-ld method leaves your system linker intact.
Step 3: Verify It’s Working
Build a small project and check the output of ldd and file. The binary should be identical (functionally) to one linked with GNU ld or mold. For LTO, add -flto to your compiler flags and confirm that the plugin is invoked (Wild will log a message if it loads a plugin).
Linker Plugin API and LTO: A Closer Look
Because the plugin API is a major 0.9 feature, let’s unpack what it enables.
Traditional Linking Without LTO
1. Compile each .c/.cpp file to native object code (.o).
2. Link all .o files together.
3. Optimisations (e.g., inlining, constant propagation) are limited to single translation units.
LTO with a Linker Plugin
1. Compiler outputs LLVM bitcode (or similar intermediate representation) instead of native code.
2. At link time, the linker loads the plugin.
3. The plugin reads all bitcode, runs cross‑module optimisation passes, then generates native code.
4. The linker performs final relocations.
Why this is slow historically – The plugin step runs only after all bitcode is read, often using a single thread, and can consume gigabytes of memory. However, Wild’s plugin implementation can still benefit from its parallel architecture during the final native code generation (the plugin itself decides how to parallelise).
What Wild 0.9 gives you – The mechanism to use LTO. Not a faster LTO itself, but compatibility so you aren’t forced back to ld or mold when you want whole‑program optimisation.
FAQ
Q: Is Wild Linker stable enough for production use?
A: Version 0.9 is still pre‑1.0, but many developers use it daily for Linux workloads. It lacks some advanced features (e.g., cross‑linking to other architectures, incremental linking). For most application codebases, it’s reliable. For safety‑critical or embedded work, test thoroughly.
Q: How does Wild compare to mold?
A: Both are orders of magnitude faster than GNU ld. mold is more mature (used in large projects like Chromium) and supports more output formats. Wild offers a Rust codebase, which some teams prefer for memory safety and easier contributions. Performance is comparable, with Wild often slightly faster on very large inputs due to different parallelisation strategies.
Q: Can I use Wild on macOS or Windows?
A: Not yet. Version 0.9 lays the groundwork for Mach‑O (macOS) and WebAssembly, but those targets are incomplete. For now, stick to Linux.
Q: What about debuggers (gdb, lldb)?
A: Wild emits standard DWARF debug information. Debugging works exactly as it does with any other linker. No changes required.
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