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- Call OPENSSL_thread_stop on thread termination (DLL_THREAD_DETACH) to prevent a memory leak in case OpenSSL is linked statically. - Warn in libcurl-thread.3 that if OpenSSL is linked statically then it may require thread cleanup. OpenSSL may need per-thread cleanup to stop a memory leak. For Windows and Cygwin if libcurl was built as a DLL then we can do that for the user by calling OPENSSL_thread_stop on thread termination. However, if libcurl was built statically then we do not have notification of thread termination and cannot do that for the user. Also, there are several other unusual cases where it may be necessary for the user to call OPENSSL_thread_stop, so in the libcurl-thread warning I added a link to the OpenSSL documentation. Co-authored-by: Viktor Szakats Reported-by: southernedge@users.noreply.github.com Reported-by: zmcx16@users.noreply.github.com Ref: https://www.openssl.org/docs/man3.0/man3/OPENSSL_thread_stop.html#NOTES Fixes https://github.com/curl/curl/issues/12327 Closes https://github.com/curl/curl/pull/12408
82 lines
2.1 KiB
Markdown
82 lines
2.1 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: curl_global_cleanup
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Section: 3
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Source: libcurl
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See-also:
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- curl_global_init (3)
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- libcurl (3)
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- libcurl-thread (3)
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Protocol:
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- All
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---
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# NAME
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curl_global_cleanup - global libcurl cleanup
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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void curl_global_cleanup(void);
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~~~
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# DESCRIPTION
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This function releases resources acquired by curl_global_init(3).
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You should call curl_global_cleanup(3) once for each call you make to
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curl_global_init(3), after you are done using libcurl.
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This function is thread-safe since libcurl 7.84.0 if
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curl_version_info(3) has the CURL_VERSION_THREADSAFE feature bit set
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(most platforms).
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If this is not thread-safe, you must not call this function when any other
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thread in the program (i.e. a thread sharing the same memory) is running.
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This does not just mean no other thread that is using libcurl. Because
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curl_global_cleanup(3) calls functions of other libraries that are
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similarly thread unsafe, it could conflict with any other thread that uses
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these other libraries.
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See the description in libcurl(3) of global environment requirements for
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details of how to use this function.
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# CAUTION
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curl_global_cleanup(3) does not block waiting for any libcurl-created
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threads to terminate (such as threads used for name resolving). If a module
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containing libcurl is dynamically unloaded while libcurl-created threads are
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still running then your program may crash or other corruption may occur. We
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recommend you do not run libcurl from any module that may be unloaded
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dynamically. This behavior may be addressed in the future.
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libcurl may not be able to fully clean up after multi-threaded OpenSSL
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depending on how OpenSSL was built and loaded as a library. It is possible in
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some rare circumstances a memory leak could occur unless you implement your own
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OpenSSL thread cleanup. Refer to libcurl-thread(3).
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# EXAMPLE
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~~~c
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int main(void)
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{
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curl_global_init(CURL_GLOBAL_DEFAULT);
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/* use libcurl, then before exiting... */
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curl_global_cleanup();
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}
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~~~
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# AVAILABILITY
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Added in 7.8
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# RETURN VALUE
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None
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