未定义Ubuntu 12.04.1 LTS libssl libcrypto上的引用

Question

我有一系列的错误，我已经添加了-l ssl and -l crypto。但是，我不知道需要安装哪个版本库

/usr/include/boost/asio/ssl/detail/openssl_init.hpp:48: undefined reference to `SSL_library_init'
/usr/include/boost/asio/ssl/detail/openssl_init.hpp:49: undefined reference to `SSL_load_error_strings'
/usr/include/boost/asio/ssl/detail/openssl_init.hpp:50: undefined reference to `SSL_library_init'
/usr/include/boost/asio/ssl/detail/openssl_init.hpp:52: undefined reference to `CRYPTO_num_locks'
/usr/include/boost/asio/ssl/detail/openssl_init.hpp:55: undefined reference to `CRYPTO_set_locking_callback'
/usr/include/boost/asio/ssl/detail/openssl_init.hpp:56: undefined reference to `CRYPTO_set_id_callback'
/usr/include/boost/asio/ssl/detail/openssl_init.hpp:48: undefined reference to `SSL_library_init'
/usr/include/boost/asio/ssl/detail/openssl_init.hpp:49: undefined reference to `SSL_load_error_strings'

有许多选项，例如

Note, selecting 'libss7-dbg' for regex 'libssl*'
Note, selecting 'libssl0.9.8-dbg' for regex 'libssl*'
Note, selecting 'libss7-dev' for regex 'libssl*'
Note, selecting 'libssl0.9.8' for regex 'libssl*'
Note, selecting 'libss2' for regex 'libssl*'
Note, selecting 'libssm-dev' for regex 'libssl*'
Note, selecting 'libssl' for regex 'libssl*'
Note, selecting 'libssh-4' for regex 'libssl*'
Note, selecting 'libssh-2-dev' for regex 'libssl*'
Note, selecting 'libssh-2-doc' for regex 'libssl*'
Note, selecting 'libssl1.0.0' for regex 'libssl*'
Note, selecting 'libsscm3' for regex 'libssl*'
Note, selecting 'libssl-ocaml-dev' instead of 'libssl-ocaml-dev-l8h98'
Note, selecting 'libssl-ocaml' instead of 'libssl-ocaml-l8h98'
Note, selecting 'libssreflect-ocaml' instead of 'libssreflect-ocaml-kevs8'
Note, selecting 'libssreflect-ocaml-dev' instead of 'libssreflect-ocaml-dev-kevs8'
Note, selecting 'python-libssh2' instead of 'python2.7-libssh2'
libss2 is already the newest version.

和

Note, selecting 'libcryptokit-ocaml' for regex 'libcrypto*'
Note, selecting 'libcryptokit-ocaml-02n31' for regex 'libcrypto*'
Note, selecting 'libcryptgps-ocaml-dev' for regex 'libcrypto*'
Note, selecting 'libcrypt-blowfish-perl' for regex 'libcrypto*'
Note, selecting 'libcrypt-saltedhash-perl' for regex 'libcrypto*'
Note, selecting 'libcrypt-gcrypt-perl' for regex 'libcrypto*'
Note, selecting 'libcryptui' for regex 'libcrypto*'
Note, selecting 'libcrypt-generatepassword-perl' for regex 'libcrypto*'
Note, selecting 'libcrypt-dh-gmp-perl' for regex 'libcrypto*'
Note, selecting 'libcrypt-cbc-perl' for regex 'libcrypto*'
Note, selecting 'libcrypt-dsa-perl' for regex 'libcrypto*'
Note, selecting 'libcrypt-dh-perl' for regex 'libcrypto*'
Note, selecting 'libcrypt-openssl-bignum-perl' for regex 'libcrypto*'
Note, selecting 'libcryptgps-ocaml-dev' instead of 'libcryptgps-ocaml-dev-1zmb9'
Note, selecting 'libcryptokit-ocaml' instead of 'libcryptokit-ocaml-02n31'
Note, selecting 'libcryptokit-ocaml-dev' instead of 'libcryptokit-ocaml-dev-02n31'

g++ -pthread -l ssl -lcrypto IpcManagerMain.cpp -o IpcManagerMain.o  -lentity++ -lpersistence++ -lplatform++ -lreflection++ -lmonitor++ -lmeta++ -lipc++ -lbroadcast++ -lutilities++ -L/usr/lib          -lboost_serialization -lboost_thread-mt -lboost_date_time -lboost_iostreams -lboost_program_options -lboost_filesystem -lboost_system

还有更多，但我已经缩短了。有人能给我指个方向吗？

Answer 1

想象一下(想象中的)链接器试图链接这些模块：

link moda modb modc modd

链接器不会(出于效率原因)记录它在moda中看到的所有符号，以尝试将它们与modb中的符号进行匹配。例如，如果moda是一个巨大的库，那么如果moda的所有符号在整个过程中都被记住，那么链接过程就会变得非常慢(并且消耗内存)。

因此，链接器总是只记住(到目前为止)丢失的符号，并试图在之后的模块中找到它们。请注意，这只适用于库。这是因为同一个库/应用程序的对象可能具有循环依赖性。

例如，这意味着只在modc和modd中搜索缺少的符号，而不在moda中搜索(同样，如果moda、modc和modd是库)。

因此，如果您有使用mody符号的modx，那么您必须在link命令中的modx之后提到mody。

例如，如果你有文件main.o、funcs.o和libmatrix.a，那么你需要这样写你的链接命令：

gcc funcs.o main.o -lmatrix

否则，如果您编写gcc -lmatrix funcs.o main.o，libmatrix.a的符号将对funcs.o和main.o不可见。