cURL / Docs / Project Documentation / Report Bugs

Report Bugs


1.1 There are still bugs
1.2 Where to report
1.3 What to report
1.4 libcurl problems
1.5 Who will fix the problems
1.6 How to get a stack trace
1.7 Bugs in libcurl bindings

1.1 There are still bugs

Curl and libcurl have grown substantially since the beginning. At the time of writing (January 2013), there are about 83,000 lines of source code, and by the time you read this it has probably grown even more.

Of course there are lots of bugs left. And lots of misfeatures.

To help us make curl the stable and solid product we want it to be, we need bug reports and bug fixes.

1.2 Where to report

If you can't fix a bug yourself and submit a fix for it, try to report an as detailed report as possible to a curl mailing list to allow one of us to have a go at a solution. You can optionally also post your bug/problem at curl's bug tracking system over at

Please read the rest of this document below first before doing that!

If you feel you need to ask around first, find a suitable mailing list and post there. The lists are available on

1.3 What to report

When reporting a bug, you should include all information that will help us understand what's wrong, what you expected to happen and how to repeat the bad behavior. You therefore need to tell us:

- your operating system's name and version number

- what version of curl you're using (curl -V is fine)

- versions of the used libraries that libcurl is built to use

- what URL you were working with (if possible), at least which protocol

and anything and everything else you think matters. Tell us what you expected to happen, tell use what did happen, tell us how you could make it work another way. Dig around, try out, test. Then include all the tiny bits and pieces in your report. You will benefit from this yourself, as it will enable us to help you quicker and more accurately.

Since curl deals with networks, it often helps us if you include a protocol debug dump with your bug report. The output you get by using the -v or --trace options.

If curl crashed, causing a core dump (in unix), there is hardly any use to send that huge file to anyone of us. Unless we have an exact same system setup as you, we can't do much with it. Instead we ask you to get a stack trace and send that (much smaller) output to us instead!

The address and how to subscribe to the mailing lists are detailed in the MANUAL file.

1.4 libcurl problems

First, post all libcurl problems on the curl-library mailing list.

When you've written your own application with libcurl to perform transfers, it is even more important to be specific and detailed when reporting bugs.

Tell us the libcurl version and your operating system. Tell us the name and version of all relevant sub-components like for example the SSL library you're using and what name resolving your libcurl uses. If you use SFTP or SCP, the libssh2 version is relevant etc.

Showing us a real source code example repeating your problem is the best way to get our attention and it will greatly increase our chances to understand your problem and to work on a fix (if we agree it truly is a problem).

Lots of problems that appear to be libcurl problems are actually just abuses of the libcurl API or other malfunctions in your applications. It is advised that you run your problematic program using a memory debug tool like valgrind or similar before you post memory-related or "crashing" problems to us.

1.5 Who will fix the problems

If the problems or bugs you describe are considered to be bugs, we want to have the problems fixed.

There are no developers in the curl project that are paid to work on bugs. All developers that take on reported bugs do this on a voluntary basis. We do it out of an ambition to keep curl and libcurl excellent products and out of pride.

But please do not assume that you can just lump over something to us and it will then magically be fixed after some given time. Most often we need feedback and help to understand what you've experienced and how to repeat a problem. Then we may only be able to assist YOU to debug the problem and to track down the proper fix.

We get reports from many people every month and each report can take a considerable amount of time to really go to the bottom with.

1.6 How to get a stack trace

First, you must make sure that you compile all sources with -g and that you don't 'strip' the final executable. Try to avoid optimizing the code as well, remove -O, -O2 etc from the compiler options.

Run the program until it cores.

Run your debugger on the core file, like '<debugger> curl core'. <debugger> should be replaced with the name of your debugger, in most cases that will be 'gdb', but 'dbx' and others also occur.

When the debugger has finished loading the core file and presents you a prompt, enter 'where' (without the quotes) and press return.

The list that is presented is the stack trace. If everything worked, it is supposed to contain the chain of functions that were called when curl crashed. Include the stack trace with your detailed bug report. It'll help a lot.

1.7 Bugs in libcurl bindings

There will of course pop up bugs in libcurl bindings. You should then primarily approach the team that works on that particular binding and see what you can do to help them fix the problem.

If you suspect that the problem exists in the underlying libcurl, then please convert your program over to plain C and follow the steps outlined above.