Add example to try and reproduce failure.

Author: ioquatix

examples/pgfault/config.ru

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+require "rdkafka"
+
+run do |env|
+	[200, {"content-type" => "text/plain"}, ["Hello, World!"]]
+end

examples/pgfault/falcon.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+require "falcon/environment/rack"
+
+service "hello.localhost" do
+	include Falcon::Environment::Rack
+end

examples/pgfault/gems.locked

@@ -0,0 +1,95 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    async (2.23.1)
+      console (~> 1.29)
+      fiber-annotation
+      io-event (~> 1.9)
+      metrics (~> 0.12)
+      traces (~> 0.15)
+    async-container (0.24.0)
+      async (~> 2.22)
+    async-container-supervisor (0.5.1)
+      async-container (~> 0.22)
+      async-service
+      io-endpoint
+      memory-leak (~> 0.5)
+    async-http (0.88.0)
+      async (>= 2.10.2)
+      async-pool (~> 0.9)
+      io-endpoint (~> 0.14)
+      io-stream (~> 0.6)
+      metrics (~> 0.12)
+      protocol-http (~> 0.49)
+      protocol-http1 (~> 0.30)
+      protocol-http2 (~> 0.22)
+      traces (~> 0.10)
+    async-http-cache (0.4.5)
+      async-http (~> 0.56)
+    async-pool (0.10.3)
+      async (>= 1.25)
+    async-service (0.13.0)
+      async
+      async-container (~> 0.16)
+    console (1.30.2)
+      fiber-annotation
+      fiber-local (~> 1.1)
+      json
+    falcon (0.51.1)
+      async
+      async-container (~> 0.20)
+      async-container-supervisor (~> 0.5.0)
+      async-http (~> 0.75)
+      async-http-cache (~> 0.4)
+      async-service (~> 0.10)
+      bundler
+      localhost (~> 1.1)
+      openssl (~> 3.0)
+      protocol-http (~> 0.31)
+      protocol-rack (~> 0.7)
+      samovar (~> 2.3)
+    ffi (1.17.2-arm64-darwin)
+    fiber-annotation (0.2.0)
+    fiber-local (1.1.0)
+      fiber-storage
+    fiber-storage (1.0.1)
+    io-endpoint (0.15.2)
+    io-event (1.10.0)
+    io-stream (0.6.1)
+    json (2.11.3)
+    localhost (1.5.0)
+    mapping (1.1.3)
+    memory-leak (0.5.2)
+    metrics (0.12.2)
+    mini_portile2 (2.8.8)
+    openssl (3.3.0)
+    protocol-hpack (1.5.1)
+    protocol-http (0.49.0)
+    protocol-http1 (0.34.0)
+      protocol-http (~> 0.22)
+    protocol-http2 (0.22.1)
+      protocol-hpack (~> 1.4)
+      protocol-http (~> 0.47)
+    protocol-rack (0.11.2)
+      protocol-http (~> 0.43)
+      rack (>= 1.0)
+    rack (3.1.13)
+    rake (13.2.1)
+    rdkafka (0.21.0)
+      ffi (~> 1.15)
+      mini_portile2 (~> 2.6)
+      rake (> 12)
+    samovar (2.3.0)
+      console (~> 1.0)
+      mapping (~> 1.0)
+    traces (0.15.2)
+
+PLATFORMS
+  arm64-darwin
+
+DEPENDENCIES
+  falcon
+  rdkafka (~> 0.21.0)
+
+BUNDLED WITH
+   2.6.7

examples/pgfault/gems.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem "falcon"
+
+group :preload do
+	gem 'rdkafka', '~> 0.21.0'
+end

examples/pgfault/readme.md

@@ -0,0 +1,32 @@
+# Objective-C Segfault
+
+On macOS, some usage of the Objective-C runtime can cause issues when forking. This is a known issue but is not specifically a bug in Falcon.
+
+## Usage
+
+### Run the server
+
+```bash
+bundle exec falcon host
+```
+
+It should start correctly with no errors.
+
+Now, comment out the preload group:
+
+``` ruby
+# group :preload do
+	gem 'rdkafka', '~> 0.21.0'
+# end
+```
+
+If you run the server again, it will fail:
+
+```
+objc[9330]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
+objc[9330]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
+ 2.33s    error: Async::Container::Forked [oid=0xa00] [ec=0xc30] [pid=8967] [2025-04-27 11:15:58 +0900]
+               | {
+               |   "status": "pid 9330 SIGABRT (signal 6)"
+               | }
+```