Beman Dawes wrote:
What can be done? Basically, adding a mutex for MT build and adding a warning to docs are the variants. Opinions?
There is already a general race-condition warning in the docs. See www.boost.org/libs/filesystem/doc/index.htm#Race-condition.
True, I've missed that.
Even if the filesystem library itself were made thread-safe, the problem could still happen because the state of the external file system may be altered by some other process or other machine.
Is there a issue with solving your particular problem by either using your own mutex, or catching and discarding the exception, or moving the create_directory() call to prolog code that is single-threaded?
No issues with those, I only wanted to make sure this problem is known. After more though, I wonder if create_directories should not swallow exceptions itself. E.g. try { create_directory(ph); } catch(const filesystem_error& e) { if (e.error() == filesystem::already_exists_error) ; // do nothing else throw; } After all, caller only cares if directory exists, if it was created by another thread it's ok. - Volodya