bold

bold - the bold linker

Bold used to be emerald, but due to time constraints and other commitments I am unable to develop and maintain the other drivers. Emerald now lives in another repo -> kubkon/emerald-old.

bold is a drop-in replacement for Apple system linker ld, written fully in Zig. It is on par with the LLVM lld linker, faster than the legacy Apple ld linker, but slower than the rewritten Apple ld linker. Some benchmark results between the linkers when linking stage3-zig compiler which includes linking LLVM statically:

$ hyperfine ./bold.sh ./ld.sh ./ld_legacy.sh ./lld.sh
Benchmark 1: ./bold.sh
  Time (mean ± σ):     978.5 ms ±   9.9 ms    [User: 3083.2 ms, System: 949.2 ms]
  Range (min … max):   967.6 ms … 998.7 ms    10 runs

Benchmark 2: ./ld.sh
  Time (mean ± σ):     439.0 ms ±   5.4 ms    [User: 1769.9 ms, System: 273.1 ms]
  Range (min … max):   432.2 ms … 447.9 ms    10 runs

Benchmark 3: ./ld_legacy.sh
  Time (mean ± σ):      1.986 s ±  0.021 s    [User: 3.100 s, System: 0.221 s]
  Range (min … max):    1.968 s …  2.030 s    10 runs

Benchmark 4: ./lld.sh
  Time (mean ± σ):      1.043 s ±  0.009 s    [User: 1.206 s, System: 0.210 s]
  Range (min … max):    1.031 s …  1.060 s    10 runs

Summary
  ./ld.sh ran
    2.23 ± 0.04 times faster than ./bold.sh
    2.38 ± 0.04 times faster than ./lld.sh
    4.52 ± 0.07 times faster than ./ld_legacy.sh

In the results

bold.sh calls bold with all the required inputs and flags
ld.sh calls the rewritten Apple linker
ld_legacy.sh calls ld -ld_classic the legacy Apple linker
lld.sh calls LLVM lld linker

tl;dr bold is currently directly competing with LLVM lld but behind the Apple ld linker.

Quick start guide

Building

You will need Zig 0.13.0 in your path. You can download it from here.

$ zig build -Doptimize=ReleaseFast

You can then pass it to your system C/C++ compiler with -B or -fuse-ld flag (note that the latter is supported mainly/only by clang):

$ cat <<EOF > hello.c
#include <stdio.h>

int main() {
    fprintf(stderr, "Hello, World!\n");
    return 0;
}
EOF

# Using clang
$ clang hello.c -fuse-ld=bold

# Using gcc
$ gcc hello.c -B/path/to/bold

Testing

If you’d like to run unit and end-to-end tests, run the tests like you’d normally do for any other Zig project.

$ zig build test

Contributing