C++ Pipe, Too Many Open Files, Errno 25 - c++

Question

I have an old C++ application running on OS X (10.10/Yosemite).
When I'm debugging the application I get an exception on this following lines of code:
// create pipe
int pipefd[2];
int piperet = pipe(pipefd);
if( piperet )
{
wcsncpy(errbuf, CEmpError::GetErrorText(CEmpError::ERR_SYSTEM, L"Can't create pipe for IPC.", errno).c_str(), errbuflen);
CEmpError::LogError(errbuf);
return CEmpError::ERR_SYSTEM; //= 115
}
So the application is running and doing this lines of code a few times. After a while pipette is -1. The errno error-code is 25.
After some research, this means "Too many open files". Is there a workaround to close all these open files? Or is it possible to know which files are open too many?
When I type in Terminal ulimit -a I get:
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
file size (blocks, -f) unlimited
max locked memory (kbytes, -l) unlimited
max memory size (kbytes, -m) unlimited
open files (-n) 2560
pipe size (512 bytes, -p) 1
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 709
virtual memory (kbytes, -v) unlimited
So I'm not the super c++-pro, here the required code of lines. Guess all not needed pipes or pipefd will be closed.
// create pipe
int pipefd[2];
int piperet = pipe(pipefd);
if( piperet )
{
wcsncpy(errbuf, CEmpError::GetErrorText(CEmpError::ERR_SYSTEM, L"Can't create pipe for IPC.", errno).c_str(), errbuflen);
CEmpError::LogError(errbuf);
return CEmpError::ERR_SYSTEM;
}
CEmpError *pError = 0;
// after transfer the execution bit could be reset, so set the rights back
chmod(args[0], S_IWUSR | S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH );
pid_t pid = fork();
if(pid == 0)
{ // child process
close(pipefd[0]); // close reading end
int fd = pipefd[1];
// redirect stdout and stderr to pipe
dup2(fd, STDOUT_FILENO);
dup2(fd, STDERR_FILENO);
close(fd); // not needed anymore
// execute steup.sh with built argument list
execvp(args[0], (char**)args);
// if we ever reached this line the exec failed and we need to report error to parent process
// once we are in child process we will print the error into stdout of our child process
// and parent process will parse and return it to the caller.
char buf[128];
sprintf(buf, "setup.sh:ERROR:PI%03d",CEmpError::ERR_EXEC);
perror(buf);
// keep the process alive until the parent process got the error from the pipe and killed this child process
sleep(5);
return CEmpError::ERR_EXEC;
}
else if (pid > 0)
{ // parent process
delete[] args[0]; // release memory allocated to f.
delete[] args[3]; // release memory allocated to log f.
delete[] args[5]; // release memory allocated to pn
close(pipefd[1]);
pParser = new CPackageInstallerParser();
FILE* fp = fdopen(pipefd[0], "r");
/*int res = */setvbuf(fp, NULL, _IOLBF, 0);
try
{
pParser->ParseOutput(fp, statusCallback, statusContext, logFileName);
}
catch (CEmpError* pErr)
{
if (pErr->ErrorCode == CEmpError::ERR_EXEC)
kill(pid, SIGABRT); // the error is parsed kill the child process
pError = pErr;
}
catch (...)
{
// some exception from statusCallback
fclose(fp);
delete pParser;
pParser = NULL;
throw;
}
fclose(fp);
int stat;
// wait for the installation process to end.
waitpid(pid, &stat, 0);
if (WIFEXITED(stat) && (stat % 256 == 0) && pError == NULL)
{
// exited normally with code 0 (success)
// printf("Installed succesfully!\n");
// register succesful operation result
try
{
RegisterResult(operation);
}
catch (CEmpError* pErr)
{
pError = pErr;
}
}
else
{
if (pError == NULL) // no error was caught by parser
pError = new CEmpError(CEmpError::ERR_UNKNOWN);
//dumpError(stat);
}
}
else
pError = new CEmpError(CEmpError::ERR_FORK);
//clean up and exit
if (pParser != NULL)
delete pParser;
pParser = NULL;
int exitcode = 0;
if (pError != NULL)
{
exitcode = pError->ErrorCode;
wcsncpy(errbuf, pError->GetErrorText().c_str(), errbuflen);
pError->Log();
delete pError;
}
return exitcode;

Answer 1

You need to close the pipe FDs with close when you no longer need them.

Answer 2

You're allowed to have 2560 open files per process, so you should close the other files and/or pipes, when no longer needed.
It is always good advice to release resources, when you're done with them.