Details
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Bug
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Resolution: Fixed
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Not Evaluated
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None
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6.5.2
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Windows
Description
The following piece of code starts a master process, then a slave from master. Master has a data stream attached to slave and also is reading from slave when ready. Slave reads data and writes it back. It is run on Windows, Qt 6.5.
#include <QtCore> #define dumpval(x) qDebug()<<#x<<'='<<x void slave() { QCoreApplication::setApplicationName("slave"); qDebug()<<"started"; QFile input, output; QDataStream inputStream{&input}, outputStream{&output}; dumpval(input.open(stdin, QFile::ReadOnly)); dumpval(output.open(stdout, QFile::WriteOnly)); QByteArray data; do { inputStream >> data; outputStream << data; dumpval(data); } while (inputStream.status() == QDataStream::Ok && !data.isEmpty()); dumpval(inputStream.status()); } void master() { QCoreApplication::setApplicationName("master"); qDebug()<<"started"; QProcess p; p.setProgram(QCoreApplication::applicationFilePath()); p.setArguments({"slave"}); p.setProcessChannelMode(QProcess::ForwardedChannels); p.start(); p.waitForStarted(); QDataStream stream(&p); QByteArray data; stream << "this is a test" << QByteArray{}; while (true) { stream.startTransaction(); stream >> data; if (stream.commitTransaction()) { dumpval(data); if (data.isEmpty()) break; } else p.waitForReadyRead(); } p.waitForFinished(); } int main(int argc, char** argv) { QCoreApplication app(argc, argv); qSetMessagePattern("%{appname}: %{message}"); if (app.arguments().size() < 2) master(); else slave(); qDebug() << "stopped"; } #include "main.moc"
The output, from DebugView, is (the very first entry is supposedly irrelavent):
00000001 0.00000000 [12452] "game restart 0" 00000002 6.64763594 [6324] master: started 00000003 6.65141678 [6324] master: process started 00000004 6.67225885 [3024] slave: started 00000005 6.67228985 [3024] slave: input.open(stdin, QFile::ReadOnly) = true 00000006 6.67232132 [3024] slave: output.open(stdout, QFile::WriteOnly) = true 00000007 80.25774384 [3024] slave: data = "this is a test\x00" 00000008 80.25778961 [3024] slave: data = "" 00000009 80.25782776 [3024] slave: inputStream.status() = 0 00000010 80.25794220 [3024] slave: stopped
3 strange things I cannot understand;
1. Everything stops at [3024] slave: output.open(stdout, QFile::WriteOnly) = true. The rest of output comes after I manually stop master.
2. No master outputting the result from stream (never readyRead?)
3. Master does not even output 'stopped' at the end.
What I expect from output:
master: started slave: started slave: input.open(stdin, QFile::ReadOnly) = true slave: output.open(stdout, QFile::WriteOnly) = true slave: data = "this is a test\x00" slave: data = "" slave: inputStream.status() = 0 slave: stopped master: data = "this is a test\x00" master: data = "" master: stopped
The output obtained on Linux is as expected (complete output from master and no hanging during outputting).