Support flush() on ostream.

[pikapi12321]

I noticed that flush() is a private member of ostream and cannot be called outside. I don't understand why it is designed to be private.

[vitaut]

A PR to make flush public is welcome.

[vitaut]

Made flush public in bba0a9d. Thanks for the suggestion.

[pikapi12321]

Made flush public in bba0a9d. Thanks for the suggestion.

I've tried public flush() in my project's logger. It seems that flush() is not safe if another thread is constantly calling ostream::print() on the same ostream object. My debug build ran ok while my release build encountered segmentation fault. Problem went away after I removed my flushes.

[vitaut]

ostream is not thread-safe as mentioned in the docs: https://fmt.dev/latest/api.html#os-api. If you want to write from multiple threads you should use a different API or add synchronization.

[bl-ue]

Hey @vitaut! v8.0.1 was released a month before this feature...will you please consider cutting a new release?

[bl-ue]

In the meantime, do you know of any way to flush the stream?

[vitaut]

This is too minor for a dedicated release and will be part of the regular release in a couple of months. In the meantime you can pin to the specific commit that adds flush or use the standard FILE API.