Grabbing Mac Computer Name through C++ Interop hangs

efroemling · November 14, 2023, 10:17pm

I'm defining a simple call in swift to grab the name of the local Mac:

public func getMacName() -> String {
  return Host.current().localizedName ?? "Unknown"
}

Then I call this from C++ as follows:

  std::string val = TestApp::getMacName();

I'm finding that If my Mac is named "Eric’s MacBook Pro" then the C++ call to getMacName() hangs. If I take out the fancy apostrophe character then it returns.
Here's what it's up to when hung:

Hard coding the Swift function to return the exact value "Eric’s MacBook Pro" does not hang. And printing the name in Swift before returning it shows the correct name was fetched; it just gets stuck on its way out to C++ land.

This is using Xcode 15.0.1 and I've repro'd the hanging behavior on Sonoma 14.1.1 Arm and on Monterey 12.7.1 Intel.

I wanted to post this here first in case its another manifestation of the other string/container issues I recently ran into recently. If this looks to be a separate and valid issue then I'm happy to put together a full repro case on GitHub or whatnot.

Alex_L · November 14, 2023, 10:34pm

Thanks for the report, could you file a GitHub issue? I'll see if I can reproduce in the meantime. It sounds like it hangs whilst traversing utf8 codepoints while casting the Swift string to a C++ string.

efroemling · November 14, 2023, 10:36pm

Sure thing; I'll get that going right now

efroemling · November 14, 2023, 11:03pm

Ok, GitHub issue is up:

github.com/apple/swift

Grabbing Mac computer name through C++ Interop hangs

opened 11:01PM - 14 Nov 23 UTC

efroemling

bug triage needed

**Description** I've found that defining a simple function in Swift to grab the name of the local Mac and calling that from C++ can hang if the Mac name contains particular characters. **Steps to reproduce** The following steps reproduce the crash for me using XCode 15.0.1 (15A507) on an M1 Max MBP running Sonoma 14.1.1: - Create a new ‘Command Line Tool’ project named “TestCommand”. - Create a new C++ file named ‘test’ (with header). Click ‘Create Bridging Header’ when it asks. - In TestCommand-Bridging-Header.h, add: ```c++ #include "test.hpp" ``` - In test.hpp, add: ```c++ void doTest(); ``` - In test.cpp, add: ```c++ #include <TestCommand-Swift.h> void doTest() { printf("Getting Mac name via Swift...\n"); std::string val = TestCommand::getMacName(); printf("Got Mac name: %s\n", val.c_str()); } ``` - In main.swift, add: ```swift // Expose a call for C++ to use. public func getMacName() -> String { return Host.current().localizedName ?? "Unknown" } // Call our C++ function that runs the test. doTest() ``` - Under build settings for the TestCommand target, set C++ and Objective-C Interoperability to “C++/Objective C++” - You should now be able to build and run the project. - Now, depending on the name of the Mac (as per System Settings -> General), running should either print the name or hang indefinitely. In my case, if my Mac is named "Eric’s MacBook Pro" I get a hang, but if I remove the apostrophe then the run completes. - Interestingly, hard-coding the Swift function to return the exact string "Eric’s MacBook Pro" succeeds, whatever that might imply.  **Environment** - Swift compiler version info: swift-driver version: 1.87.1 Apple Swift version 5.9 (swiftlang-5.9.0.128.108 clang-1500.0.40.1) - Xcode version info: Xcode 15.0.1 Build version 15A507 - Deployment target: macOS Sonoma 14.1.1 (23B81). Also repro'd on Monterey 12.7.1 (21G920)