Allegro 5.0 - 为什么我会收到链接器错误？

Question

I recently compiled Allegro-5.0 from source (following the instructions from the wiki). I didn't get any errors during the process, so I assume it went well. However, I am getting linker errors with even the most minimal test programs:

//test.cpp
#include <allegro5/allegro.h>

int main()
{
    al_init();
    return 0;
}

I am compiling with

g++ `pkg-config --libs allegro-5.0` test.cpp -o test

But I always get

/tmp/ccVmmERa.o: In function `main':
test.cpp:(.text+0xf): undefined reference to `al_install_system'
collect2: error: ld returned 1 exit status

(pkg-config returns -L/usr/local/lib -lallegro, there doesn't seem to be anything wrong with that)

Also, I can compile the examples with the the given makefile just fine, so there doesn't seem to be anything wrong with the library. I would just try to do the same thing the makefile does to make it work, but I don't understand it at all (I can barely write my own simple ones).

Oh, and I'm using Ubuntu 11.10 and gcc 4.7, though I don't think that has anything to do with it.

So - why does this happen, and how can I fix it?

Answer 1

Put the libs last on the command line:

g++ test.cpp -o test `pkg-config --libs allegro-5.0`

When linking, the order of the files and libraries matter.