Hello, I'd like to find an available TCP port. I came up with this code: #!/usr/bin/env swift import Foundation import Network func findAvailablePort() -> UInt16 { let semaphore = DispatchSemaphore(value: 0) let listener = try! NWListener(using: .tcp, on: .any) listener.stateUpdateHandler = { state in switch state { case .ready: semaphore.signal() case .failed(let e): fatalError(e.localizedDescription) default: break } } listener.newConnectionHandler = { conn in } listener.start(queue: .global()) let timeout = DispatchTime.now() + DispatchTimeInterval.seconds(5) if semaphore.wait(timeout: timeout) == .timedOut { fatalError("timeout") } return listener.port!.rawValue } print(findAvailablePort()) Any feedback, especially around error handling, would be very appreciated. (The two error conditions I've identified, network error and semaphore timeout, seem unlikely to hit so I reached for fatalError.) To give some more context, I'm writing an application with processes A and B. A starts B via Process(). B will listen on a TCP socket but A needs to know which one. (I'd rather not use stdio to let it know.) So A will find a free tcp port, start B, and pass port in argv. There's obviously a possible race condition between finding the free port and listening on it but it seems unlikely to hit given the OS doesn't seem to "recycle" free ports right away.

Hello, On a x86_64 host I'm building an executable that uses JIT (asmjit) and dynamically loads a library. When running on arm64, running that executable segfaults: Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000058 Exception Note: EXC_CORPSE_NOTIFY Termination Signal: Segmentation fault: 11 Termination Reason: Namespace SIGNAL, Code 0xb Terminating Process: exc handler [2107] I'm using the following entitlements: <key>com.apple.security.cs.allow-jit</key> <true/> <key>com.apple.security.cs.allow-unsigned-executable-memory</key> <true/> <key>com.apple.security.cs.allow-dyld-environment-variables</key> <true/> <key>com.apple.security.cs.disable-library-validation</key> <true/> and that's how I sign it: codesign \ --sign "-" \ --verbose=4 \ --options=runtime \ --entitlements=erts/etc/darwin/Entitlements.plist \ release/*/erts-*/bin/* I noticed that when JIT is disabled, everything works fine. When JIT is enabled, but there's no disable-library-validation entitlement, there's no segfault but loading the library fails: dlopen(/Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so, 2): no suitable image found. Did find: /Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so: code signature in (/Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so) not valid for use in process using Library Validation: mapped file has no cdhash, completely unsigned? Code has to be at least ad-hoc signed. /Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so: stat() failed with errno=35 If I code sign the library: codesign \ --sign "-" \ --verbose=4 \ --options=runtime \ release/*/lib/crypto-*/priv/lib/crypto.so then the error becomes: dlopen(/Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so, 2): no suitable image found. Did find: /Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so: code signature in (/Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so) not valid for use in process using Library Validation: mapped file has no Team ID and is not a platform binary (signed with custom identity or adhoc?) /Users/wojtek/otp/lib/crypto-5.0.3/priv/lib/crypto.so: stat() failed with errno=35 In terms of reproducing this issue, unfortunately I wasn't able to create a minimal program that does it. You should see the error when following https://github.com/erlang/otp/pull/5036#issuecomment-933397076 though. Any guidance would be very appreciated.