Text
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Write Ruby extension using
Zig
@nishidayuya
2025-04-17
Agileware Drinkup at RubyKaigi 2025 LT
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@nishidayuya (GitHub, X)
NaCl’s programmer. Matz is our fellow.
from Ruby City Matz-e（松江市）
now Matz-yama city（松山市）
i collected RubyKaigi 2024 X posts.
from #rubykaigiA #rubykaigiB #rubykaigiC
#rubykaigi #rubykaigi2024
to https://togetter.com/li/2369438
i will collect RubyKaigi 2025’s, too! (posfie)
1/20
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Write Ruby
extension
using Zig
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what? Write Ruby extension
using Zig
many Ruby extension using C.
Rust can write, too:
bundle gem --ext=rust foo
since bundler-3.4.0 (ruby-3.2.0 is bundled)
4/20
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what’s Zig?
a programming language.
Zig can write dynamic link library as C, Rust, and
so on.
↓
Zig can write Ruby extension, I think
↓
try it!
5/20
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today, i will:
write a method, by Zig code.
call it.
then output return value.
ruby -r./zig-out/lib/libzig_ruby_module.so \
-e 'p(ZigRubyModule.add(1, 2))'
6/20
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step0: run “zig init”
$ zig init
info: created build.zig
info: created build.zig.zon
info: created src/main.zig
info: created src/root.zig
info: see `zig build --help` for a menu of options
7/20
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step1: write entrypoint
Init_{so name} function
const ruby = @cImport(@cInclude("ruby/ruby.h"));
//...
pub export fn Init_libzig_ruby_module() void {
const rb_mZigRubyModule =
ruby.rb_define_module("ZigRubyModule");
ruby.rb_define_singleton_method(
rb_mZigRubyModule,
"add",
rb_mZigRubyModule_s_add,
2,
);
}
8/20
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step2: implement method
fn rb_mZigRubyModule_s_add(...) callconv(.c) ruby.VALUE {
var ap = @cVaStart();
defer @cVaEnd(&ap);
}
_ = @cVaArg(&ap, ruby.VALUE); // dummy
const o1 = @cVaArg(&ap, ruby.VALUE);
const o2 = @cVaArg(&ap, ruby.VALUE);
const n1 = ruby.NUM2INT(o1);
const n2 = ruby.NUM2INT(o2);
const sum = add(n1, n2);
return ruby.INT2NUM(sum);
9/20
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step3: fix build rule
diff --git a/build.zig b/build.zig
index d8a38d8..62eb5c3 100644
--- a/build.zig
+++ b/build.zig
@@ -48,10 +48,17 @@ pub fn build(b: *std.Build) void {
// This creates a `std.Build.Step.Compile`, which is the build step responsible
// for actually invoking the compiler.
const lib = b.addLibrary(.{
-
.linkage = .static,
+
.linkage = .dynamic,
.name = "zig_ruby_module",
.root_module = lib_mod,
});
+
// ruby -rmkmf -e 'p(RbConfig::CONFIG["libdir"])'
+
lib.addLibraryPath(std.Build.LazyPath{ .cwd_relative = "/home/yuya/.local/share/mise/installs/ruby/3.4.3/lib" });
+
// ruby -rmkmf -e 'p(RbConfig::CONFIG["rubyhdrdir"])'
+
lib.addIncludePath(std.Build.LazyPath{ .cwd_relative = "/home/yuya/.local/share/mise/installs/ruby/3.4.3/include/ruby-3.4.0" });
+
// ruby -rmkmf -e 'p(RbConfig::CONFIG["rubyarchhdrdir"])'
+
lib.addIncludePath(std.Build.LazyPath{ .cwd_relative = "/home/yuya/.local/share/mise/installs/ruby/3.4.3/include/ruby-3.4.0/x86_64-linux" });
+
lib.linkSystemLibrary("c");
// This declares intent for the library to be installed into the standard
// location when the user invokes the "install" step (the default step when
10/20
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demo
zig init
write Init_libzig_ruby_module
implement method
fn rb_mZigRubyModule_s_add(...) callconv(.c)
ruby.VALUE {
fix build rule
ruby -r./zig-out/lib/libzig_ruby_module.so
-e 'p(ZigRubyModule.add(1, 2))'
12/20
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i was writing
CFP for
RubyKaigi
2025,
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i was writing CFP for
RubyKaigi 2025, but…
i found a blog:
written by Paweł Świątkowski on 2022-12-25!
(zig-0.14.0 (current version) cannot build it.)
i sent pull-request to fix it.
16/20
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i was writing
CFP for
RubyKaigi
2025, but…
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i could not
write CFP.
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Thanks!
by
@nishidayuya
![](6.png "today, i will:
write a method, by Zig code.
call it.
then output return value.
ruby -r./zig-out/lib/libzig_ruby_module.so \
-e 'p(ZigRubyModule.add(1, 2))'
6/20")
![](mini-6.png "today, i will:
write a method, by Zig code.
call it.
then output return value.
ruby -r./zig-out/lib/libzig_ruby_module.so \
-e 'p(ZigRubyModule.add(1, 2))'
6/20")
