What could be wrong here? I have the following simple class:
这可能有什么问题？我有以下简单的类：
#include "libmnl/libmnl.h"
int main() {
struct mnl_socket *a = mnl_socket_open(12);
}
And after running a simple gcc compile (gcc -lmnl main.c) I get the following errors:
运行简单的gcc编译（gcc -lmnl main.c）后，我收到以下错误：
/tmp/cch3GjuS.o: In function `main':
main.c:(.text+0xe): undefined reference to `mnl_socket_open'
collect2: ld returned 1 exit status
Running nm on the shared library shows that it's actually found:
在共享库上运行nm表明它实际上已找到：
aatteka@aatteka-Dell1:/tmp$ nm -D /usr/lib/libmnl.so | grep mnl_socket_open
0000000000001810 T mnl_socket_open
This is happening on Ubuntu 12.04. The libmnl-dev and libmnl0 packages are installed. The strace output of gcc indicates that ld is using exactly that *.so file:
这种情况发生在Ubuntu 12.04上。安装了libmnl-dev和libmnl0软件包。 gcc的strace输出表明ld正在使用* .so文件：
[pid 10988] stat("/usr/lib/gcc/x86_64-linux-gnu/4.6/libmnl.so", 0x7fff2a39b470) = -1 ENOENT (No such file or directory)
[pid 10988] open("/usr/lib/gcc/x86_64-linux-gnu/4.6/libmnl.so", O_RDONLY) = -1 ENOENT (No such file or directory)
[pid 10988] stat("/usr/lib/gcc/x86_64-linux-gnu/4.6/libmnl.a", 0x7fff2a39b4d0) = -1 ENOENT (No such file or directory)
[pid 10988] open("/usr/lib/gcc/x86_64-linux-gnu/4.6/libmnl.a", O_RDONLY) = -1 ENOENT (No such file or directory)
[pid 10988] stat("/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/libmnl.so", 0x7fff2a39b470) = -1 ENOENT (No such file or directory)
[pid 10988] open("/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/libmnl.so", O_RDONLY) = -1 ENOENT (No such file or directory)
[pid 10988] stat("/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/libmnl.a", 0x7fff2a39b4d0) = -1 ENOENT (No such file or directory)
[pid 10988] open("/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/libmnl.a", O_RDONLY) = -1 ENOENT (No such file or directory)
[pid 10988] stat("/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libmnl.so", {st_mode=S_IFREG|0644, st_size=18608, ...}) = 0
[pid 10988] open("/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libmnl.so", O_RDONLY) = 7
1 个解决方案
#1
34
Libraries must be listed after the objects that use them (more precisely, a library will be used only if it contains a symbol that satisfies an undefined reference known at the time it is encountered). Move the -lmnl to the end of the command.
必须在使用它们的对象之后列出库（更确切地说，只有当库包含满足遇到未知定义的未定义引用的符号时才会使用库）。将-lmnl移动到命令的末尾。
#1
34
Libraries must be listed after the objects that use them (more precisely, a library will be used only if it contains a symbol that satisfies an undefined reference known at the time it is encountered). Move the -lmnl to the end of the command.
必须在使用它们的对象之后列出库（更确切地说，只有当库包含满足遇到未知定义的未定义引用的符号时才会使用库）。将-lmnl移动到命令的末尾。