diff options
Diffstat (limited to 'src/corelib/io/qprocess.cpp')
| -rw-r--r-- | src/corelib/io/qprocess.cpp | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp index 49ba04068a7..16447033ca1 100644 --- a/src/corelib/io/qprocess.cpp +++ b/src/corelib/io/qprocess.cpp @@ -1574,7 +1574,7 @@ std::function<void(void)> QProcess::childProcessModifier() const Sets the \a modifier function for the child process, for Unix systems (including \macos; for Windows, see setCreateProcessArgumentsModifier()). The function contained by the \a modifier argument will be invoked in the - child process after \c{fork()} is completed and QProcess has set up the + child process after \c{fork()} or \c{vfork()} is completed and QProcess has set up the standard file descriptors for the child process, but before \c{execve()}, inside start(). The modifier is useful to change certain properties of the child process, such as setting up additional file descriptors or closing @@ -1595,6 +1595,15 @@ 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 On some systems (notably, Linux), QProcess will 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() */ void QProcess::setChildProcessModifier(const std::function<void(void)> &modifier) |