Safety of curl_easy_pause in callback

[jay]

PR #12046 added to the documentation that curl_easy_pause could be called within callbacks:

"Unlike most other libcurl functions, curl_easy_pause can be used from within callbacks."

The thing is if you unpause a connection in a callback then couldn't it call the write callback and flip the in-callback bit to off?

For example:

• libcurl sets Curl_set_in_callback(data, true); then calls user's progress function
• progress function calls curl_easy_pause to unpause
• curl_easy_pause causes libcurl to set Curl_set_in_callback(data, true); then calls user's write function
• write function returns and libcurl sets Curl_set_in_callback(data, false); even though still in user's progress function

Are there other ways this could be an issue, like callback recursion if curl_easy_pause calls back into the user's progress function?

[bagder]

This can become an issue if the callback calls another libcurl function (after curl_easy_pause() ) that is not allowed. Which then will be allowed due to the bug you mention above.