Why is QsslSocket working with Qt 5.3 but not Qt 5.7 on Debian Stretch?

原文地址：https://stackoverflow.com/questions/42094214/why-is-qsslsocket-working-with-qt-5-3-but-not-qt-5-7-on-debian-stretch

方便以后查找，复制过来

question：

I have an app that uses the
QWebSocket class but not SSL. It works fine when I execute a version compiled with Qt 5.3 but a Qt 5.7 executable freezes on the following warnings:

QSslSocket: cannot resolve CRYPTO_num_locks
QSslSocket: cannot resolve CRYPTO_set_id_callback
QSslSocket: cannot resolve CRYPTO_set_locking_callback
QSslSocket: cannot resolve ERR_free_strings
QSslSocket: cannot resolve EVP_CIPHER_CTX_cleanup
QSslSocket: cannot resolve EVP_CIPHER_CTX_init
QSslSocket: cannot resolve sk_new_null
QSslSocket: cannot resolve sk_push
QSslSocket: cannot resolve sk_free
QSslSocket: cannot resolve sk_num
QSslSocket: cannot resolve sk_pop_free
QSslSocket: cannot resolve sk_value
QSslSocket: cannot resolve SSL_library_init
QSslSocket: cannot resolve SSL_load_error_strings
QSslSocket: cannot resolve SSL_get_ex_new_index
QSslSocket: cannot resolve SSLv2_client_method
QSslSocket: cannot resolve SSLv3_client_method
QSslSocket: cannot resolve SSLv23_client_method
QSslSocket: cannot resolve SSLv2_server_method
QSslSocket: cannot resolve SSLv3_server_method
QSslSocket: cannot resolve SSLv23_server_method
QSslSocket: cannot resolve X509_STORE_CTX_get_chain
QSslSocket: cannot resolve OPENSSL_add_all_algorithms_noconf
QSslSocket: cannot resolve OPENSSL_add_all_algorithms_conf
QSslSocket: cannot resolve SSLeay
QSslSocket: cannot resolve SSLeay_version
QSslSocket: cannot call unresolved function CRYPTO_num_locks
QSslSocket: cannot call unresolved function CRYPTO_set_id_callback
QSslSocket: cannot call unresolved function CRYPTO_set_locking_callback
QSslSocket: cannot call unresolved function SSL_library_init
QSslSocket: cannot call unresolved function SSLv23_client_method
QSslSocket: cannot call unresolved function sk_num

I am not seeing these warnings in the 5.3 version (that works properly), which suggests that I should not ignore them, as asked in this question. Also,

QT += network

is already in my src.pro.

I was led to believe that Debian dropped these symbols from the openssl package. Could anyone tell me what's going on here and how I could fix this?

大神的回答：

From this
answer about OpenSSL and Qt, I found a hint and I displayed SSL library version used for compile-time and run-time using:

qDebug()<<"SSL version use for build: "<<QSslSocket::sslLibraryBuildVersionString();
qDebug()<<"SSL version use for run-time: "<<QSslSocket::sslLibraryVersionNumber();
qDebug()<<QCoreApplication::libraryPaths();

And it displays:

SSL version use for build:  "OpenSSL 1.0.1e-fips 11 Feb 2013"
... lot of SSL warnings...
SSL version use for run-time:  0
("/opt/Qt/5.8/gcc_64/plugins", "/home/Project/..../build...Desktop_Qt_5_8_0_GCC_64bit-Release/src/release/build_linux_64")

But Debian Stretch is shipped with OpenSSl 1.1. As expected, all the threads on the Web about this issue are true: this is an OpenSSL library version compatibility issue.

I "apt install libssl1.0-dev" and the problem was solved. I still have 2 SSL warnings about SSLv3, but at least this is only warning (I read something on the Web about it, no way to find it again).

SSL version use for build:  "OpenSSL 1.0.1e-fips 11 Feb 2013"
QSslSocket: cannot resolve SSLv3_client_method
QSslSocket: cannot resolve SSLv3_server_method
SSL version use for run-time:  268443839
("/opt/Qt/5.8/gcc_64/plugins", "/home/Project/..../build...Desktop_Qt_5_8_0_GCC_64bit-Release/src/release/build_linux_64")