From c3f02df42f7c98615bec99aa385a0fb7d787bb39 Mon Sep 17 00:00:00 2001
From: Jarred Sumner <jarred@jarredsumner.com>
Date: Wed, 30 Jul 2025 20:56:15 -0700
Subject: [PATCH] Add a way to voluntarily crash on stack overflow in CI

---
 scripts/runner.node.mjs                | 1 +
 src/bun.js/bindings/JSGlobalObject.zig | 6 ++++++
 src/bun.zig                            | 6 ++++++
 src/feature_flags.zig                  | 2 ++
 4 files changed, 15 insertions(+)

diff --git a/scripts/runner.node.mjs b/scripts/runner.node.mjs
index a681c27baa..604f7dd8c2 100755
--- a/scripts/runner.node.mjs
+++ b/scripts/runner.node.mjs
@@ -1040,6 +1040,7 @@ async function spawnBun(execPath, { args, cwd, timeout, env, stdout, stderr }) {
     SHELL: shellPath,
     FORCE_COLOR: "1",
     BUN_FEATURE_FLAG_INTERNAL_FOR_TESTING: "1",
+    BUN_FEATURE_FLAG_CRASH_ON_STACK_OVERFLOW: "1",
     BUN_DEBUG_QUIET_LOGS: "1",
     BUN_GARBAGE_COLLECTOR_LEVEL: "1",
     BUN_JSC_randomIntegrityAuditRate: "1.0",
diff --git a/src/bun.js/bindings/JSGlobalObject.zig b/src/bun.js/bindings/JSGlobalObject.zig
index 7cbada9a94..e35a4169e8 100644
--- a/src/bun.js/bindings/JSGlobalObject.zig
+++ b/src/bun.js/bindings/JSGlobalObject.zig
@@ -4,6 +4,12 @@ pub const JSGlobalObject = opaque {
     }
     extern fn JSGlobalObject__throwStackOverflow(this: *JSGlobalObject) void;
     pub fn throwStackOverflow(this: *JSGlobalObject) void {
+        if (comptime bun.Environment.is_canary) {
+            if (bun.getRuntimeFeatureFlag(.BUN_FEATURE_FLAG_CRASH_ON_STACK_OVERFLOW)) {
+                @panic("Stack overflow");
+            }
+        }
+
         JSGlobalObject__throwStackOverflow(this);
     }
     extern fn JSGlobalObject__throwOutOfMemoryError(this: *JSGlobalObject) void;
diff --git a/src/bun.zig b/src/bun.zig
index c40a89e73d..c88d30ecdb 100644
--- a/src/bun.zig
+++ b/src/bun.zig
@@ -3730,6 +3730,12 @@ pub const StackCheck = struct {
 // Workaround for lack of branch hints.
 pub noinline fn throwStackOverflow() StackOverflow!void {
     @branchHint(.cold);
+    if (comptime bun.Environment.is_canary) {
+        if (bun.getRuntimeFeatureFlag(.BUN_FEATURE_FLAG_CRASH_ON_STACK_OVERFLOW)) {
+            @panic("Stack overflow");
+        }
+    }
+
     return error.StackOverflow;
 }
 const StackOverflow = error{StackOverflow};
diff --git a/src/feature_flags.zig b/src/feature_flags.zig
index 7e0cf90912..ecff505ecc 100644
--- a/src/feature_flags.zig
+++ b/src/feature_flags.zig
@@ -40,6 +40,8 @@ pub const RuntimeFeatureFlag = enum {
     BUN_NO_CODESIGN_MACHO_BINARY,
     BUN_TRACE,
     NODE_NO_WARNINGS,
+
+    BUN_FEATURE_FLAG_CRASH_ON_STACK_OVERFLOW,
 };
 
 /// Enable breaking changes for the next major release of Bun