[openssl-users] Openssl static build linked in DLL does not unload on win32
matt at openssl.org
Fri Jan 6 14:54:59 UTC 2017
On 06/01/17 14:36, Dan Heinz wrote:
>>> On 04/01/17 23:11, Dan Heinz wrote: Using openssl 1.1.0c.
>>> I have a test application that is a win32 console app that calls
>>> a win32 DLL which has the openssl libraries linked in
>>> The test applications uses late-binding to the DLL and calls
>>> LoadLibrary for the DLL, one test function in the DLL, and then
>>> FreeLibrary on the DLL.
>>> The test function in the DLL does the following:
>>> RSA*rsa = NULL;
>>> rsa = RSA_new();
>>> When FreeLibrary is called on the DLL, dllmain in never called
>>> with any messages. A subsequent call to LoadLibrary also fails
>>> to call dllmain and when the test function is called RSA_new()
>>> fails. This leads me to believe the DLL is never freed.
>>> I have tried building openssl with and without no-threads with
>>> the same results. My build parameters are: perl Configure
>>> --prefix=*%RootPath_ThirdParty%*\*%OPENSSL_VERSION%* -DPURIFY
>>> -DOPENSSL_NO_COMP -D_USING_V110_SDK71_ no-shared no-threads
>>> no-asm no-idea no-mdc2 no-rc5 no-ssl3 no-zlib no-comp
>>> What am I missing?
>> OpenSSL does its cleanup at *process* exit. Don't call
>> OPENSSL_cleanup() explicitly - this is >discouraged.
>> From this manpage:
"Typically there should be no need to call this function directly as it
is initiated >automatically on application exit...<snip>...
>> Once OPENSSL_cleanup() has been called the library cannot be
>> This last sentence is the reason why RSA_new() will fail after you
>> have previously called >OPENSSL_cleanup().
>> Because cleanup happens on process exit, OpenSSL will keep itself
>> in memory until that time >(otherwise crashes will occur because
>> the cleanup routines have been unloaded).
>> If you want to dynamically load and unload your DLL then don't
>> statically link it to OpenSSL - >otherwise OpenSSL will keep your
>> DLL around until process exit too.
> That is very disappointing. As a library vendor we have no control
> over how our users load and unload our libraries. We will just have
> to roll back to 1.0.x and wait to see if this will be addressed.
> Also, as Jakob stated in another post, it really seems like this
> design will be problematic.
Can you not link against the OpenSSL DLLs rather than statically link?
That would avoid the problem.
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