gcc 的 -ldl 参数是什么意思？

[rrfeng]

情景：
编译安装 keepalived，需要 openssl-devel 的库

但是 openssl 也是编译安装的，安装目录是 /usr/local/openssl

keepalived configure 的时候，无论是
--libdir=/usr/local/openssl
还是
LDFLAGS="$LDFLAGS -L/usr/local/openssl" ；
或者指定 /usr/local/openssl/lib /usr/local/openssl/include 等目录

均提示 OpenSSL 库找不到。



最终在
LDFLAGS="-ldl" ./configure
的时候编译成功了，成功的自动找到了 openssl 中相关文件

[wwwjfy]

-llibrary
-l library
Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.)

It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, foo.o -lz
bar.o searches library z after file foo.o but before bar.o. If bar.o refers to functions in z, those functions may not be loaded.

The linker searches a standard list of directories for the library, which is actually a file named liblibrary.a. The linker then uses this file as if it had been specified
precisely by name.

The directories searched include several standard system directories plus any that you specify with -L.

Normally the files found this way are library files---archive files whose members are object files. The linker handles an archive file by scanning through it for members which
define symbols that have so far been referenced but not defined. But if the file that is found is an ordinary object file, it is linked in the usual fashion. The only difference
between using an -l option and specifying a file name is that -l surrounds library with lib and .a and searches several directories.


-L 只是加入搜索库的路径，-l指定要链接的库
-ldl, dl就是库的名字

[seupengdi]

就是libdl.so吧 某种有用的动态库