Return CURLE_WRITE_ERROR when CURLOPT_WRITEFUNCTION callback returns CURL_WRITEFUNC_ERROR

[enwillyado]

I did this

Make a CURLOPT_WRITEFUNCTION callback that returns CURL_WRITEFUNC_ERROR in order to abort the curl session.

For instance, if a large download need to be aborted without errors by user.

I expected the following

The cURL session must return CURLE_ABORTED_BY_CALLBACK.

curl/libcurl version

lib environment, last version

operating system

Unix ARM.

[icing]

So, what did you see instead? What is the failure you'd like to report?

[enwillyado]

See the chop_write function:

curl/lib/sendf.c

Line 334 in 6ec70a9

if(wrote != chunklen) {

When a CURLOPT_WRITEFUNCTION callback called, the return size was stored in wrote variable. This function checks if the returned value was CURL_WRITEFUNC_PAUSE. If the special CURL_WRITEFUNC_ERROR return negative value is returned, a generic CURLE_WRITE_ERROR. Get the specific CURLE_ABORTED_BY_CALLBACK error is better in order to distinguish a non-error-condition status from a generic-error status when aborting curl session.

[enwillyado]

Probably this report should be a suggestion to have a CURL_WRITEFUNC_ABORT special returned value, right?

[bagder]

I still don't understand. Your callback returns CURL_WRITEFUNC_ERROR.

What are you saying is returned and what are you saying you think should have been returned?

[enwillyado]

Yes, literally if the CURLOPT_WRITEFUNCTION callback needs to return a abort, now only CURL_WRITEFUNC_ERROR can used. Then, if this special value was returned, the curl sessions ends with CURLE_WRITE_ERROR final code. This is the same final code if callbacks get an error (not memory or something like this)... in this case, by returning a amount that differs from the amount passed by curl, is enough.

So, my suggestion is: return CURLE_ABORTED_BY_CALLBACK when callback returns CURL_WRITEFUNC_ERROR, or better, make a new CURL_WRITEFUNC_ABORT special return value to use in callbacks in order to get the curl session final code CURLE_ABORTED_BY_CALLBACK.

[bagder]

Yes, maybe CURLE_ABORTED_BY_CALLBACK would be slightly more logical to use, but I am reluctant to change this now that it has been in use like this since 7.87.0. Applications and users have already adapted to this return code and I fear that changing it now might cause more problems than simply accepting defeat and better documenting the current state.

[enwillyado]

Thanks @bagder , please, consider to add a new CURL_WRITEFUNC_ABORT special return value for Callbacks in order to get a CURLE_ABORTED_BY_CALLBACK response code from curl session!

[bagder]

consider to add a new CURL_WRITEFUNC_ABORT special return value for Callbacks in order to get a CURLE_ABORTED_BY_CALLBACK response code from curl session!

I like this idea!