CURLOPT_NOSIGNAL might be a MUST to make threaded use work, like on AIX 5.2

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 http://www.gnu.org/software/gnutls/manual/html_node/Multi_002dthreaded-applications.html

When using multiple threads you should set the CURLOPT_NOSIGNAL option to

TRUE for all handles. Everything will work fine except that timeouts are not

honored during the DNS lookup - which you can work around by building libcurl

with c-ares support. c-ares is a library that provides asynchronous name

resolves. Unfortunately, c-ares does not yet support IPv6.

When using multiple threads you should set the CURLOPT_NOSIGNAL option to TRUE

for all handles. Everything will or might work fine except that timeouts are

not honored during the DNS lookup - which you can work around by building

libcurl with c-ares support. c-ares is a library that provides asynchronous

name resolves. Unfortunately, c-ares does not yet fully support IPv6. On some

platforms, libcurl simply will not function properly multi-threaded unless

this option is set.

Also, note that CURLOPT_DNS_USE_GLOBAL_CACHE is not thread-safe.