Initialize pid_t variable - c++

Question

I have an error reported by Valgrind:
==5644== Conditional jump or move depends on uninitialised value(s)
This is happening for a variable of type pid_t.
My code is the following:
GmpPipePlayer::GmpPipePlayer( IOBase *pIO, Referee *pBack, PieceColor pc, int size, const DataBoard *pBd, int handicap, const char *cmd_line, int bDebug )
: GmpPlayer(pIO, pBack, pc, size, pBd, handicap, bDebug)
{
int down[2], up[2];
pid_t _pid; //here the var is declared
pipe(down);
pipe(up);
_pid = fork();
if (_pid < 0)
exit(1);
if (_pid == 0)
{
close(down[1]);
close(up[0]);
dup2(down[0], 0);
dup2(up[1], 1);
execl("/bin/sh", "sh", "-c", cmd_line, NULL);
_exit(1);
}
close(down[0]);
close(up[1]);
_down = down[1];
_up = up[0];
_reader_thd = new Thread(reader_wrapper, this);
}
GmpPipePlayer::~GmpPipePlayer()
{
if (_pid > 0) //valgrind is reporting that the error is here!!
{
kill(_pid, SIGTERM);
_pid = 0;
}
if (_up)
{
close(_up);
_up = 0;
}
if (_down)
{
close(_down);
_down = 0;
}
delete _reader_thd
}
So, I think the problem is the _pid is not initialized, how should initialize this variable? I tried in this way:
pid_t _pid=0;
but this is still causing the same error. That piece of code is called many times during the process.

Answer 1

It appears that you have two variables called _pid - the local that you declared in the constructor:
pid_t _pid; //here the var is declared
and the one that you access in the destructor:
if (_pid > 0) //valgrind is reporting that the error is here!!
These variables are not the same: the one that you access in the destructor must be a global or an instance variable (more likely).
Since you rely on _pid to pass the state from the constructor to the destructor, you need to remove the local declaration from the constructor, and initialize the other _pid as appropriate. If it is an instance variable, add its initialization to the initializer list, like this:
GmpPipePlayer::GmpPipePlayer( IOBase *pIO, Referee *pBack, PieceColor pc, int size, const DataBoard *pBd, int handicap, const char *cmd_line, int bDebug )
: GmpPlayer(pIO, pBack, pc, size, pBd, handicap, bDebug), _pid(0) {
... // HERE ------------------^
}