qt.network.ssl: QSslSocket: cannot resolve CRYPTO_num_locks
qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_id_callback
qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_locking_callback
qt.network.ssl: QSslSocket: cannot resolve ERR_free_strings
qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_cleanup
qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_init
qt.network.ssl: QSslSocket: cannot resolve sk_new_null
qt.network.ssl: QSslSocket: cannot resolve sk_push
qt.network.ssl: QSslSocket: cannot resolve sk_free
qt.network.ssl: QSslSocket: cannot resolve sk_num
qt.network.ssl: QSslSocket: cannot resolve sk_pop_free
qt.network.ssl: QSslSocket: cannot resolve sk_value
qt.network.ssl: QSslSocket: cannot resolve SSL_library_init
qt.network.ssl: QSslSocket: cannot resolve SSL_load_error_strings
qt.network.ssl: QSslSocket: cannot resolve SSL_get_ex_new_index
qt.network.ssl: QSslSocket: cannot resolve SSLv23_client_method
qt.network.ssl: QSslSocket: cannot resolve SSLv23_server_method
qt.network.ssl: QSslSocket: cannot resolve X509_STORE_CTX_get_chain
qt.network.ssl: QSslSocket: cannot resolve OPENSSL_add_all_algorithms_noconf
qt.network.ssl: QSslSocket: cannot resolve OPENSSL_add_all_algorithms_conf
qt.network.ssl: QSslSocket: cannot resolve SSLeay
qt.network.ssl: QSslSocket: cannot resolve SSLeay_version
qt.network.ssl: QSslSocket: cannot call unresolved function SSLeay
qt.network.ssl: Incompatible version of OpenSSL
分析问题：是因为Qt依赖的OpenSSL和系统自带的OpenSSL1.1.1g版本不同。Qt5.9.7需要OpenSSL1.0
下载并安装openssl-1.0.2h，（安装gsoap也会用到）
https://www.openssl.org/source/old/1.0.2/openssl-1.0.2h.tar.gz
下载保存在： ～/Download目录下
$ cd ~/Download
$ tar zxvf openssl-1.0.2h.tar.gz
$ cd openssl-1.0.2h
$ ./config enable-shared
$ make depend
$ make
$ make test
$ sudo make install
默认安装路径是"/usr/local/ssl"
以下步骤参考链接：https://www.freesion.com/article/3437146790/；同样适用于CentOS8下的Qt5.9.7
将编译生成的四个文件考到Qt目录（/home/david/MySoft/Qt5.8.0/5.8/gcc_64/lib/）下面（这样会把系统自带的openssl也降级别，危险）：
libcrypto.so libssl.so libcrypto.so.1.0.0 libssl.so.1.0.0
应该最好在目录/home/david/MySoft/Qt5.8.0/5.8/下面新建MyQtSSL，将libcrypto.so libssl.so libcrypto.so.1.0.0 libssl.so.1.0.0 拷贝到：/home/david/MySoft/Qt5.8.0/5.8/MyQtSSL 目录下面。然后在Qtcreator 增加动态库路径（如下图）：
至于为什么不拷贝到 /home/david/MySoft/Qt5.8.0/5.8/gcc_64/lib/ 下面，那是因为一般CentOS安装Qt会在 .bashrc 文件下面。
export LD_LIBRARY_PATH=${LD_LIBRARY_LIB}:/home/david/MySoft/Qt5.8.0/5.8/gcc_64/lib
这样就会影响到整个系统的PATH，系统自带的openssl功能被覆盖。
