diff options
Diffstat (limited to 'src/corelib/io/qprocess.cpp')
| -rw-r--r-- | src/corelib/io/qprocess.cpp | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp index ddcd7a4768a..ff33607fa16 100644 --- a/src/corelib/io/qprocess.cpp +++ b/src/corelib/io/qprocess.cpp @@ -853,6 +853,15 @@ void QProcessPrivate::Channel::clear() is useful to ensure any ignored (\c SIG_IGN) signal does not affect the child's behavior. + \value UseVFork Requests that QProcess use \c{vfork(2)} to start the child + process. Use this flag to indicate that the callback function set + with setChildProcessModifier() is safe to execute in the child side of + a \c{vfork(2)}; that is, the callback does not modify any non-local + variables (directly or through any function it calls), nor attempts + to communicate with the parent process. It is implementation-defined + if QProcess will actually use \c{vfork(2)} and if \c{vfork(2)} is + different from standard \c{fork(2)}. + \sa setUnixProcessParameters(), unixProcessParameters() */ @@ -1646,6 +1655,16 @@ std::function<void(void)> QProcess::childProcessModifier() const "async-signal-safe" is advised). Most of the Qt API is unsafe inside this callback, including qDebug(), and may lead to deadlocks. + \note If the UnixProcessParameters::UseVFork flag is set via + setUnixProcessParameters(), QProcess may use \c{vfork()} semantics to + start the child process, so this function must obey even stricter + constraints. First, because it is still sharing memory with the parent + process, it must not write to any non-local variable and must obey proper + ordering semantics when reading from them, to avoid data races. Second, + even more library functions may misbehave; therefore, this function should + only make use of low-level system calls, such as \c{read()}, + \c{write()}, \c{setsid()}, \c{nice()}, and similar. + \sa childProcessModifier(), setUnixProcessParameters() */ void QProcess::setChildProcessModifier(const std::function<void(void)> &modifier) |