Question

Here’s my C method to get the pid of the Finder process. GetProcessInformation() is causing a segfault. Why?

Here’s the function:

static OSStatus
GetFinderPID(pid_t *pid)
{
    ProcessSerialNumber psn = {kNoProcess, kNoProcess};
    ProcessInfoRec info;
    OSStatus status = noErr;

    info.processInfoLength = sizeof(ProcessInfoRec);
    info.processName = nil;

    while (!status)
    {
        status = GetNextProcess(&psn);
        if (!status)
        {
            status = GetProcessInformation(&psn, &info);
        }
        if (!status &&
            info.processType == 'FNDR' &&
            info.processSignature == 'MACS')
        {
            return GetProcessPID(&psn, pid);
        }
    }

    return status;
}

Here’s the backtrace:

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000032aaaba7
0x00007fffffe00623 in __bzero ()
(gdb) bt
#0  0x00007fffffe00623 in __bzero ()
#1  0x00007fff833adaed in CreateFSRef ()
#2  0x00007fff833ab53b in FSPathMakeRefInternal ()
#3  0x00007fff852fc32d in _CFGetFSRefFromURL ()
#4  0x00007fff852fbfe0 in CFURLGetFSRef ()
#5  0x00007fff85dd273f in GetProcessInformation ()
#6  0x0000000100000bef in GetFinderPID [inlined] () at /path/to/main.c:21

Answer 1

Zeroing out the ProcessInfoRect struct worked, rather than trying to determine which individual fields should be zeroed.