[mac/linux] tango.sys.Process hangs (blocker for bin/bob, after compiling first Tango module)

Try the new binary attached to #1846

tango.sys.Process hangs in this line: "dup2(pout.sink.fileHandle(), STDOUT_FILENO);". Testcase:

import tango.sys.Process;
void main()
{
  auto p = new Process("echo \"Hello\"\n", null);
  p.execute();
}

Hm... I have no idea what bin or bob is. I don't understand the report at all..

Can someone with MacOS experience please explain what the issue is to a unix/windows guy? :)

You'll find various bobs under build/bin/ ;) It is a tango building app. The issue here appears to be that, on Mac OSX, Process (which bob uses) hangs.

A minimal testcase is provided by mwarning in one of the comments.

larsivi, bob mac binary from #1846 for ldc worked fine, thanks! should the ticket be closed now?

No, there is still a problem with Process - although it may be a DMD bug.

Can I duplicate this on Linux? What DMD version does this happen with? I don't have access to Mac OSX, so I don't know if I can fix this :(

Recently, dmd2 was changed to treat static array arguments as value types, I don't think dmd 1 should have been affected. But dup2 does take int[2] as an argument, so maybe this has something to do with that -- maybe it only affects MAC.

Sorry about the bob/bin ignorance, I haven't built Tango in a long time.

I have the same problem on linux. So it's probably not just a mac problem.

dmd version?

dmd 1.056.

I just came across the problem too (Linux, DMD 1.057), and it's a blocker on linux for me (works fine on windows though), and I've been trying to trace it. I don't know if this helps, but what I've found out so far:

(Using the test app above, but, for simplicity, I changed the string being passed to the Process constructor to just "echo")

If you modify the line "dup2(pout.sink.fileHandle(), STDOUT_FILENO);" (ie the line that has been hangs) to "fcntl(tmp, F_DUPFD, STDOUT_FILENO);", then the program continues all the way to the line "rc = execve(path.ptr, argv.ptr, (envp.length == 0 ? environ : envp.ptr));" at which point it hangs again.

At that point the trail seems to grow cold (at least for me) because all the params to execve seem to check out ok (at least as far as I can tell). 'path.ptr' points to "/bin/echo\0" (which is correct for me). 'argv.length' is 2. 'argv[0]' points to "echo\0". 'argv[1]' is null. 'envp.length' is 1. 'envp[0]' is null.

I'm changing the summary slightly to better reflect the real issue.

Correction to my previous post:

"fcntl(tmp, F_DUPFD, STDOUT_FILENO);"

should be:

"fcntl(pout.sink.fileHandle(), F_DUPFD, STDOUT_FILENO);"

Another correction: DMD 1.056

My earlier post was referring to the child process. Regardless of whether or not you make the change I mentioned in the child process, the parent process always hangs on this line:

pexec.source.input.read((cast(byte*) &status)[0 .. status.sizeof]);

If you do make change I mentioned in the child process, the child *does* successfully run echo.

Although, for all I know, I might have screwed up my own results by using Stdout for debugging output...

bugfix

Looks like the problem was an orphaned if.

(In [5376]) Comment orphaned if, my mistake, thanks mwarning and wm4 for finding it, closes #1859, closes #1861