[LLVMbugs] [Bug 18869] New: ExecuteAndWait fails when called second time on OSX

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Mon Feb 17 07:53:10 PST 2014


            Bug ID: 18869
           Summary: ExecuteAndWait fails when called second time on OSX
           Product: libraries
           Version: trunk
          Hardware: Macintosh
                OS: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: Support Libraries
          Assignee: unassignedbugs at nondot.org
          Reporter: elviss at elviss.lv
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The second call to ExecuteAndWait returns -1, because Wait sets ChildPid to -1,
and catches EINTR the first time it is called. Subsequent Wait calls return pid
of previous processes and fail.
The following code produces the error on OSX, no problems for other platforms.

int main()
    const char* args0[] = { "/bin/ls", NULL};
    std::cout << llvm::sys::ExecuteAndWait(args0[0], args0) << "\n";

    //wait until the first one finishes

    const char* args1[] = { "/bin/pwd", NULL};
    std::cout << llvm::sys::ExecuteAndWait(args1[0], args1) << "\n";

    return 0;

Commenting line 335 in /lib/Support/Unix/Program.inc (ChildPid = -1; // mimic a
wait() using waitpid()) fixes the problem and I think it is OK to wait only for
the launched process not for any process to finish. LLVM 3.3 was looping until
waitpid returned the correct pid, that way Wait also works correctly.

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