[swift-dev] Failed to launch REPL process

[Ron Olson]

Hi all-

I am able to build Swift 4 on Fedora 26 Linux 
(https://github.com/tachoknight/swift-rpm) and while it can compile and 
run Swift code just fine, the REPL does not start because of:

error: failed to launch REPL process: process launch failed: 'A' packet 
returned an error: -1

I've been searching around and this seems common to running Swift in a 
Docker container or the Ubuntu shell in Windows. In my case I'm running 
it on a Fedora 26 virtual machine, so no Docker, no Windows.

I ran an strace on the swift process and I can see that that it tries to 
spawn a child process which is killed, leading to the error:

--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_KILLED, si_pid=6551, 
si_uid=1000, si_status=SIGINT, si_utime=0, si_stime=2} ---
write(2, "error: failed to launch REPL pro"..., 94error: failed to 
launch REPL process: process launch failed: 'A' packet returned an 
error: -1
) = 94


I get the same error if I run swift as root or sudo. I'm willing to dive 
into this issue but before I do am wondering if this is a known issue or 
there's some specific thing I haven't done to make it work. This 
particular machine is devoted only to getting Swift working on Fedora, 
so it has no extraneous stuff, no other users, etc.

Thanks for any help!

Ron