Improve runInteractiveProcess error message when working directory does not exist

Example code:

  import System.Process

  main = do
      (_, _, _, commhand) <-
          runInteractiveProcess "echo" ["something"] (Just "/no/such/dir") Nothing
      exitCode <- waitForProcess commhand
      print exitCode

This happens on Linux with both 6.6 and the latest HEAD snapshot.

I think the problem is in C code, in libraries/base/cbits/runProcess.c (6.6). Below are the important code fragments. Search for BUG HERE for a bug location.

ProcHandle
runInteractiveProcess (char *const args[],
               char *workingDirectory, char **environment,
               int *pfdStdInput, int *pfdStdOutput, int *pfdStdError)
{
    ...

    switch(pid = fork())
    {
    ...

    case 0:
    {
        pPrPr_disableITimers();

        if (workingDirectory) {
            if (chdir (workingDirectory) < 0) {
                // BUG HERE:
                // Calling return here is bad idea here. This code
                // is run in the child process and returning makes the
                // child act as if it was the parent - strange things will
                // happen!
                return -1;
            }
        }

        ...

        /* the child */
        if (environment) {
            execvpe(args[0], args, environment);
        } else {
            execvp(args[0], args);
        }
    }
    _exit(127);

    default:
    ...

I thought about sending a patch, but I'm not sure what the fix should be. Doing "_exit(SOMETHING)" instead of return seems to be better then returning, but I don't know what SOMETHING should be, and maybe there is a better solution.

I think I've seen the same problem in another run*Process function in this C file.

Trac metadata

Trac field	Value
Version	6.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries (other)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	marig1@wp.pl, tomasz.zielonka@gmail.com
Operating system	Unknown
Architecture	Unknown