Sortix 1.1dev ports manual
This manual documents Sortix 1.1dev ports. You can instead view this document in the latest official manual.
libcurl-thread(3) | libcurl thread safety | libcurl-thread(3) |
NAME
libcurl-thread - libcurl thread safetyMulti-threading with libcurl
libcurl is thread safe but has no internal thread synchronization. You may have to provide your own locking should you meet any of the thread safety exceptions below.TLS
If you are accessing HTTPS or FTPS URLs in a multi-threaded manner, you are then of course using the underlying SSL library multi-threaded and those libs might have their own requirements on this issue. You may need to provide one or two functions to allow it to function properly:- OpenSSL
- OpenSSL 1.1.0+ "can be safely used in multi-threaded
applications provided that support for the underlying OS threading API is
built-in." In that case the engine is used by libcurl in a way that
is fully thread-safe.
- GnuTLS
- https://gnutls.org/manual/html_node/Thread-safety.html
- NSS
- thread-safe already without anything required.
- Secure-Transport
- The engine is used by libcurl in a way that is fully thread-safe.
- WinSSL
- The engine is used by libcurl in a way that is fully thread-safe.
- wolfSSL
- The engine is used by libcurl in a way that is fully thread-safe.
- BoringSSL
- The engine is used by libcurl in a way that is fully thread-safe.
Other areas of caution
- Signals
- Signals are used for timing out name resolves (during DNS
lookup) - when built without using either the c-ares or threaded resolver
backends. When using multiple threads you should set the
CURLOPT_NOSIGNAL(3) option to 1L 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 or
threaded-resolver support. c-ares is a library that provides asynchronous
name resolves. On some platforms, libcurl simply will not function
properly multi-threaded unless the CURLOPT_NOSIGNAL(3) option is
set.
- Name resolving
- gethostby* functions and other system calls. These functions, provided by your operating system, must be thread safe. It is very important that libcurl can find and use thread safe versions of these and other system calls, as otherwise it can't function fully thread safe. Some operating systems are known to have faulty thread implementations. We have previously received problem reports on *BSD (at least in the past, they may be working fine these days). Some operating systems that are known to have solid and working thread support are Linux, Solaris and Windows.
- curl_global_* functions
- These functions are not thread safe. If you are using libcurl with multiple threads it is especially important that before use you call curl_global_init(3) or curl_global_init_mem(3) to explicitly initialize the library and its dependents, rather than rely on the "lazy" fail-safe initialization that takes place the first time curl_easy_init(3) is called. For an in-depth explanation refer to libcurl(3) section GLOBAL CONSTANTS.
- Memory functions
- These functions, provided either by your operating system or your own replacements, must be thread safe. You can use curl_global_init_mem(3) to set your own replacement memory functions.
- Non-safe functions
- CURLOPT_DNS_USE_GLOBAL_CACHE(3) is not thread-safe.
June 30, 2019 | libcurl 7.69.0 |