Trying to run a non-existing file in Linux results in a zombie process

[cmorve-te]

As can be seen in https://godbolt.org/z/4T7TMMTov, calling the process constructor on Linux (have not checked different launchers) asking it to execute a non-existing file results on a exception being thrown and the forked process never being reaped.

For comparison, https://godbolt.org/z/W94K31sGW uses an existing file and it works fine.

Those use Boost 1.86 since that's the latest available in Godbolt today, but I have reproduced the same issue on 1.87.

[cmorve-te]

A ::waitpid(pid, nullptr, 0); before/after

process/include/boost/process/v2/posix/default_launcher.hpp

Line 442 in b529769

detail::on_error(*this, executable, argv, ec, inits...);

fixes the problem for me. But I will let you create a proper fix.