3.QT中的debug相关的函数，以及文件锁的使用

#include
<QFile>

#include
<QMutex>  
//文件锁

void
MyMessageHandler(QtMsgType
type,const
QMessageLogContext
&context,const
QString
&msg)

{

//使用一个文件锁，当在写文件的时候，要等写完之后才能继续执行

static
QMutex
mutex;

mutex.lock();

QString
strContext;

//在QMessageLogContext中保存的有文件名，文件行号，方法等信息

strContext.sprintf("%s
%d
%s:\r\n\t",context.file,context.line,context.function);

QString
output
=
strContext
+
msg
+
"\r\n";

if(type
==
QtDebugMsg)

{

QFile
file("debug.log");

file.open(QFile::WriteOnly
|
QFile::Append);

file.write(output.toUtf8());

file.close();

}

if(type
==
QtWarningMsg)

{

QFile
file("warning.log");

file.open(QFile::WriteOnly|QFile::Append);

file.write(output.toUtf8());

file.close();

}

if(type
==
QtCriticalMsg)

{

QFile
file("critical.log");

file.open(QFile::WriteOnly
|
QFile::Append);

file.write(output.toUtf8());

file.close();

}

if(type
==
QtFatalMsg)

{

QFile
file("fatal.log");

file.open(QFile::WriteOnly
|
QFile::Append);

file.write(output.toUtf8());

file.close();

}

printf("%s",output.toUtf8().data());

mutex.unlock();

}

int
main()

{

//To
suppress
the
output
at
runtime,
install
your
own
message

//handler
with
qInstallMessageHandler().

qInstallMessageHandler(MyMessageHandler);

qDebug()
<<
"output
debug";

qDebug("%s,%d","outputdebug",1);

qWarning()
<<
"warning";

qCritical()
<<
"cridical";

//可以放开下面的一句，然后发现目录也有相应的fatal.log文件

//qFatal("fatal
info");

}

输入目录（E:\QT\build-T33Debug-Desktop_Qt_5_3_MinGW_32bit-Debug）的文件如下：