1 files changed, 25 insertions, 9 deletions
diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index 65ffec784b..8183527cdb 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -1496,11 +1496,15 @@ QByteArray QProcess::readAllStandardError()
 }
 
 /*!
-    Starts the program \a program in a new process, passing the
-    command line arguments in \a arguments. The OpenMode is set to \a
-    mode. QProcess will immediately enter the Starting state. If the
-    process starts successfully, QProcess will emit started();
-    otherwise, error() will be emitted.
+    Starts the program \a program in a new process, if one is not already
+    running, passing the command line arguments in \a arguments. The OpenMode
+    is set to \a mode.
+
+    The QProcess object will immediately enter the Starting state. If the
+    process starts successfully, QProcess will emit started(); otherwise,
+    error() will be emitted. If the QProcess object is already running a
+    process, a warning may be printed at the console, and the existing
+    process will continue running.
 
     Note that arguments that contain spaces are not passed to the
     process as separate arguments.
@@ -1597,10 +1601,10 @@ static QStringList parseCombinedArgString(const QString &program)
 /*!
     \overload
 
-    Starts the program \a program in a new process. \a program is a
-    single string of text containing both the program name and its
-    arguments. The arguments are separated by one or more
-    spaces. For example:
+    Starts the program \a program in a new process, if one is not already
+    running. \a program is a single string of text containing both the
+    program name and its arguments. The arguments are separated by one or
+    more spaces. For example:
 
     \snippet doc/src/snippets/code/src_corelib_io_qprocess.cpp 5
 
@@ -1609,6 +1613,9 @@ static QStringList parseCombinedArgString(const QString &program)
 
     \snippet doc/src/snippets/code/src_corelib_io_qprocess.cpp 6
 
+    If the QProcess object is already running a process, a warning may be
+    printed at the console, and the existing process will continue running.
+
     Note that, on Windows, quotes need to be both escaped and quoted.
     For example, the above code would be specified in the following
     way to ensure that \c{"My Documents"} is used as the argument to
@@ -1621,6 +1628,13 @@ static QStringList parseCombinedArgString(const QString &program)
 void QProcess::start(const QString &program, OpenMode mode)
 {
     QStringList args = parseCombinedArgString(program);
+    if (args.isEmpty()) {
+        Q_D(QProcess);
+        d->processError = QProcess::FailedToStart;
+        setErrorString(tr("No program defined"));
+        emit error(d->processError);
+        return;
+    }
 
     QString prog = args.first();
     args.removeFirst();
@@ -1795,6 +1809,8 @@ bool QProcess::startDetached(const QString &program,
 bool QProcess::startDetached(const QString &program)
 {
     QStringList args = parseCombinedArgString(program);
+    if (args.isEmpty())
+        return false;
 
     QString prog = args.first();
     args.removeFirst();