交叉编译百度开放云的MQTT-c时遇到的问题总结

MQTT-c 依赖photo库
photo库依赖libssl和libcrypto两个库,这两个库包在openssl中
OpenSSL 是一个强大的安全套接字层密码库，囊括主要的密码算法、常用的密钥和证书封装管理功能及SSL协议，并提供丰富的应用程序供测试或其它目的使用。

昨天编译MQTT-c 出现错误：

arm-linux-gcc -c src/PublisherSync.c -I/home/whl/output/arm-linux/include
arm-linux-gcc -o PublisherSync ConnectorSync.o PublisherSync.o -L/home/whl/output/arm-linux/lib -lpaho-mqtt3cs -I/home/whl/output/arm-linux/include -lrt
/usr/local/arm/4.2.2-eabi/usr/bin-ccache/../lib/gcc/arm-unknown-linux-gnueabi/4.2.2/../../../../arm-unknown-linux-gnueabi/bin/ld: warning: libssl.so.1.0.0, needed by /home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so, not found (try using -rpath or -rpath-link)
/usr/local/arm/4.2.2-eabi/usr/bin-ccache/../lib/gcc/arm-unknown-linux-gnueabi/4.2.2/../../../../arm-unknown-linux-gnueabi/bin/ld: warning: libcrypto.so.1.0.0, needed by /home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so, not found (try using -rpath or -rpath-link)
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_connect'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toERR_print_errors_fp’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_get1_session'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toCRYPTO_set_locking_callback’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_set_session'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toOPENSSL_add_all_algorithms_noconf’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_CTX_set_verify'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toSSL_load_error_strings’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_get_cipher_list'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toSSLeay_version’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_CTX_use_certificate_chain_file'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toSSL_free’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_CTX_set_default_passwd_cb_userdata'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toSSL_CTX_new’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_get_verify_result'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toSSL_read’
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference to SSL_set_fd'
/home/whl/output/arm-linux/lib/libpaho-mqtt3cs.so: undefined reference toSSL_pending’

这个错误很奇怪，排查了好久，因为同样的Makefile文件，交叉编译 时就报错，编译 x86版本时就很正常。
后来google到要在编译时加上 -lssl -lcrypto,就可以顺利编译通过了。