mirror of
https://github.com/oven-sh/bun
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2c0721eabe
## Summary
- Updates the docstring in static-initializers.test.ts which incorrectly
said "exactly one static initializer" - the test actually expects 2
initializers for both arm64 and x64 since the mimalloc v3 update
- Added a comment explaining that mimalloc v3 adds a static initializer
on arm64
## Background
The test file was updated in c63415c9c9 (Mimalloc v3 update) to expect 2
static initializers on arm64 (changed from 1 to 2), but the comments
were not updated to reflect this change. This PR updates the
documentation to accurately describe the expected behavior.
## Test plan
- [x] No functional changes - documentation only
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
74 lines
2.8 KiB
TypeScript
74 lines
2.8 KiB
TypeScript
import { describe, expect, it } from "bun:test";
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import { bunEnv, bunExe, isMacOSVersionAtLeast } from "harness";
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/**
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* This test prevents startup performance regressions by ensuring that Bun has
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* only the expected number of static initializers from its own executable.
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*
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* Static initializers are functions that run automatically when a program starts, before main() is called.
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* They're used to initialize global variables and static class members, but come with performance costs:
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*
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* 1. They always execute at startup, even if the initialized values are never used
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* 2. They can't be optimized away by the compiler
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* 3. They add to the binary size
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* 4. They increase startup time
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* 5. They can introduce complex initialization order dependencies
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*
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* On macOS, we can use DYLD_PRINT_INITIALIZERS to detect static initializers.
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* This test verifies that Bun has only the expected number of static initializers.
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*
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* Adding more static initializers would degrade Bun's startup performance.
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*/
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describe("static initializers", () => {
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// Only macOS has DYLD_PRINT_INITIALIZERS
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// macOS 13 has a bug in dyld that crashes if you use DYLD_PRINT_INITIALIZERS
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it.skipIf(!isMacOSVersionAtLeast(14.0))("should have the expected number of static initializers", () => {
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const env = {
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...bunEnv,
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DYLD_PRINT_INITIALIZERS: "1",
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} as const;
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const result = Bun.spawnSync({
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cmd: [bunExe(), "--version"],
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env,
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stdout: "pipe",
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stderr: "pipe",
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});
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const stdout = result.stdout.toString();
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const stderr = result.stderr.toString();
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// Check it didn't crash (and if it did, print the errors)
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try {
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expect(result.signalCode).toBeUndefined();
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expect(result.exitCode).toBe(0);
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} catch (e) {
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console.log(stderr);
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throw e;
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}
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// Verify the version was printed correctly
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expect(stdout.trim()).toMatch(/^\d+\.\d+\.\d+(-[a-z0-9.]+)?$/);
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// Combine stdout and stderr since DYLD_PRINT_INITIALIZERS output goes to stderr
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const output = stderr + stdout;
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// Get all lines that contain initializers from the bun executable
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const bunInitializers = output
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.split("\n")
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.map(a => a.trim())
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.filter(line => line.includes("running initializer") && line.includes(bunExe()));
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// On both architectures, we have one initializer "__GLOBAL__sub_I_static.c".
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// On arm64, mimalloc v3 adds one more static initializer (total: 2).
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// On x86_64, we also have:
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// - one from ___cpu_indicator_init due to our CPU feature detection
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// - one from mimalloc v3
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// (total: 3)
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expect(
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bunInitializers.length,
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`Do not add static initializers to Bun. Static initializers are called when Bun starts up, regardless of whether you use the variables or not. This makes Bun slower.`,
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).toBe(process.arch === "arm64" ? 2 : 3);
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});
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});
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