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Re: [RFC/PATCH glibc 0/2] setting working dir in posix_spawn()

On 09/08/2018 12:54 AM, Eric Blake wrote:
Also, I've realized that we do NOT need posix_spawn_file_actions_addopenat(). The main benefit of openat() is that you can redirect relative file names according to an fd of your choice, without affecting global state. But during posix_spawn(), there are no other threads competing for global state (if you are doing a library implementation where the chdir() is done between fork() and exec()), so:

openat(mydir, "file", mode);

can be decomposed to:

posix_spawn_file_actions_addopen(&act, 5, ".", O_RDONLY|O_DIRECTORY, 0);
posix_spawn_file_actions_addfchdir(&act, mydir);
posix_spawn_file_actions_addopen(&act, 4, "file", mode, 0);
posix_spawn_file_actions_addfchdir(&act, 5);
posix_spawn_file_actions_addclose(&act, 5);

Is it possible to choose an appropriate value for the directory descriptor automatically?

What about support for AT_EMPTY_PATH, for upgrading an O_PATH descriptor? I think this operation still needs openat.


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