Thanks. What was that bug number? Bug submitted via Feedback Assistant as FB24878563

That is indeed ugly. I submitted a bug report via Feedback Assistant as it’s clearly (at least to me) a regression in Xcode 27/macOS 27. In the mean time I guess I’ll make due with Xcode’s console with standard input. :-(

I just ran some additional tests. Both tests were run on clean macOS virtual machines (using UTM and the Virtualization Framework). No additional software installed other than the base OS. I can confirm that Xcode 27 on macOS 26.6.2 works fine. Terminal comes up fine and the test program displays properly. However, running the identical project (newly created, not copied) under Xcode 27 on macOS 27.0 fails with the same error. A possible regression for Xcode when running on macOS 27?

Thanks for the reply, and I apologize for not providing more detailed information about the versions involved. I'm on macOS 27.0 (26A428) on an M1 Mac mini. This behavior was seen on the released Xcode 27.0 (from the Mac App Store) and 27.1 beta downloaded from the Apple Developer web site. The issue I've seen are on C++ projects that were created under earlier versions of Xcode and last built with Xcode 26 on macOS 26. I created a new Command Line Tool project with the C++ language. I set the scheme for the build to run under Terminal. main.cpp is the following sample C++ "hello world" program: int main(int argc, const char * argv[]) { // insert code here... std::cout << "Hello, World!\n"; return EXIT_SUCCESS; } Compile/build ran fine. Same issue occurred. I also created another new project and selected the C language. I used your sample code as main.c. Same issue.