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

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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_locksQSslSocket: cannot resolve CRYPTO_set_id_callbackQSslSocket: cannot resolve CRYPTO_set_locking_callbackQSslSocket: cannot resolve ERR_free_stringsQSslSocket: cannot resolve EVP_CIPHER_CTX_cleanupQSslSocket: cannot resolve EVP_CIPHER_CTX_initQSslSocket: cannot resolve sk_new_nullQSslSocket: cannot resolve sk_pushQSslSocket: cannot resolve sk_freeQSslSocket: cannot resolve sk_numQSslSocket: cannot resolve sk_pop_freeQSslSocket: cannot resolve sk_valueQSslSocket: cannot resolve SSL_library_initQSslSocket: cannot resolve SSL_load_error_stringsQSslSocket: cannot resolve SSL_get_ex_new_indexQSslSocket: cannot resolve SSLv2_client_methodQSslSocket: cannot resolve SSLv3_client_methodQSslSocket: cannot resolve SSLv23_client_methodQSslSocket: cannot resolve SSLv2_server_methodQSslSocket: cannot resolve SSLv3_server_methodQSslSocket: cannot resolve SSLv23_server_methodQSslSocket: cannot resolve X509_STORE_CTX_get_chainQSslSocket: cannot resolve OPENSSL_add_all_algorithms_noconfQSslSocket: cannot resolve OPENSSL_add_all_algorithms_confQSslSocket: cannot resolve SSLeayQSslSocket: cannot resolve SSLeay_versionQSslSocket: cannot call unresolved function CRYPTO_num_locksQSslSocket: cannot call unresolved function CRYPTO_set_id_callbackQSslSocket: cannot call unresolved function CRYPTO_set_locking_callbackQSslSocket: cannot call unresolved function SSL_library_initQSslSocket: cannot call unresolved function SSLv23_client_methodQSslSocket: 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_methodQSslSocket: cannot resolve SSLv3_server_methodSSL 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")