QProcess::pid() gives invalid data

[shaolin]

Hi guys,

I have a strange problem. I'm doing a gui for ffmpeg, and I start ffmpeg using qprocess from within my program. It works nice, but while it's encoding I want to get ffmpeg process pid. If I try to use

QProcess::pid()

QProcess::pid()

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it gives me some random strings taken from the gui, I think it reads some invalid memory region.
How can I solve this?
Please note that I try to get the pid after the started() signal is emitted and if

qprocess::state()

qprocess::state()

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gives me "Running" and while ffmpeg is encoding, so I am 100% sure that the process is running.

Any idea?

Thx in advance

[high_flyer]

On what platform are you? windows?
If so:

typedef Q_PID

Typedef for the identifiers used to represent processes on the underlying platform. On Unix and Symbian, this corresponds to qint64; on Windows, it corresponds to _PROCESS_INFORMATION*.

typedef struct _PROCESS_INFORMATION {
  HANDLE hProcess;
  HANDLE hThread;
  DWORD  dwProcessId; //<- this is what you are after I guess.
  DWORD  dwThreadId;
} PROCESS_INFORMATION, *LPPROCESS_INFORMATION;

typedef struct _PROCESS_INFORMATION {
  HANDLE hProcess;
  HANDLE hThread;
  DWORD  dwProcessId; //<- this is what you are after I guess.
  DWORD  dwThreadId;
} PROCESS_INFORMATION, *LPPROCESS_INFORMATION;

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[shaolin]

I'm under mac and it should be a typedef qint64, but if I try to prints this value with qdebug() it print a string that is often a piece of the process command line arguments

[shaolin]

No one can help me?

[wysota]

Please provide a working minimal example reproducing the problem.

[shaolin]

... //various declarations
QProcess ffmpeg;
QObject::connect(&ffmpeg, SIGNAL(started()), this, SLOT(getPid()));
ffmpeg.start("ffmpeg -i movie.avi -y movie.mkv"); //just an example. here I call ffmpeg with right parameters to do a (long) encoding
 
... //getPid() function;
 
void getPid(){
  qdebug() << "FFmpeg pid: " + this.ffmpeg.pid(); //here often it gives me a substring of the command line, let's say for this example "-y mov", but it can happen that it gives me also other strings of my program, like it reads unclean memory
} 
 
//please note that the same piece of code, for other processes I call using QProcess, gives me the right pid

... //various declarations
QProcess ffmpeg;
QObject::connect(&ffmpeg, SIGNAL(started()), this, SLOT(getPid()));
ffmpeg.start("ffmpeg -i movie.avi -y movie.mkv"); //just an example. here I call ffmpeg with right parameters to do a (long) encoding

... //getPid() function;

void getPid(){
  qdebug() << "FFmpeg pid: " + this.ffmpeg.pid(); //here often it gives me a substring of the command line, let's say for this example "-y mov", but it can happen that it gives me also other strings of my program, like it reads unclean memory
} 

//please note that the same piece of code, for other processes I call using QProcess, gives me the right pid

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[high_flyer]

void getPid(){
  qdebug() << "FFmpeg pid: " + QString::number(this.ffmpeg.pid()); //here often it gives me a substring of the command line, let's say for this example "-y mov", but it can happen that it gives me also other strings of my program, like it reads unclean memory
}

void getPid(){
  qdebug() << "FFmpeg pid: " + QString::number(this.ffmpeg.pid()); //here often it gives me a substring of the command line, let's say for this example "-y mov", but it can happen that it gives me also other strings of my program, like it reads unclean memory
}

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[shaolin]

Stupid me, you are absolutely right! Now it works.. sorry for my silly problem..