- **status**: open --> pending
- **assigned_to**: Daniel Stenberg
- **Comment**:

There's no such thing as "built for multi-threaded". On most platform libcurl is built exactly the same no matter what and the decision to use threading or not is made by the application at run-time. So, libcurl cannot set the option depending on that.

The only real alternative I can think of would be to change the default setting of that option but that would be an ABI brekage that I am against doing.

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** [bugs:#1386] nosignal should be default in presence of multithreading**
**Status:** pending
**Created:** Fri Jun 27, 2014 12:15 AM UTC by Ami Fischman
**Last Updated:** Fri Jun 27, 2014 12:15 AM UTC
**Owner:** Daniel Stenberg
The implementation of alarms/timeouts in libcurl is thread-hostile: while the rest of libcurl is multithread-safe in that different handles can be used on different threads concurrently, alarms are implemented in terms of siglongjmp with a global/static sigjmp_buf curl_jmpenv variable shared among all threads/handles.  As a result a timed-out Curl_resolv_timeout (for example) will longjmp to an arbitrary caller, not necessarily the one that timed out.
A workaround for multithread-requiring clients is to
curl_easy_setopt(handle, CURLOPT_NOSIGNAL, true);
on all handles.
It would be better if libcurl detected that it was built for multi-threaded use and force-enable nosignal.  In other words, enforce at build-time that at most one of "!nosignal" / "threads" is enabled.
Related thread from 2006 discussing the incompatiblity: http://curl.haxx.se/mail/lib-2006-09/0214.html (but it seems to have petered out without action, which is why this bug is just asking for the build system to prevent misuse rather than asking for the underlying bug to be fixed, which is a much harder problem).
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