QProcess::UnixProcessFlag::CloseFileDescriptors takes too long

We are running an application on a docker container, the host system is using Ubuntu 25.04. The application launches a Linux command periodically, with QProcess. To avoid issues with the open file handles, we pass QProcess::UnixProcessParameters.lowestFileDescriptorToClose parameter with the value 3.

Expected result: Launch the external application without an additional wait.

Actual result: The startup of the new process takes about 2 minutes.

Suspected root cause: The docker container reports a maximum of 1073741816 file descriptor through the getrlimit(RLIMIT_NOFILE, &limit) function call, and the applyProcessParameters has a loop to iterate between [3, 1073741816[ range, and tries to close all filedescriptors in between.

Recommended solution: List open file descriptors for the newly forked process, then call close() on them, instead of iterating through the whole range.

Article about the issue can be found here