使错误未定义引用

Question

I'm using a headless image and compiling this simple code in GNU bash. I receive these linker errors

#include <IL/il.h>   
#include <IL/ilu.h> 
#include <IL/ilut.h>   
#include <stdio.h>   
#include <stdlib.h>   
#include <string.h>   

int main(int argc, char **argv)   
{     
    ILuint  ImgId;

 // Initialize DevIL.   
    ilInit();   

    // Generate the main image name to use.   
    ilGenImages(1, &ImgId);   

    // Bind this image name.   
    ilBindImage(ImgId);   

    // Loads the image specified by File into the image named by ImgId.   
    if (!ilLoadImage(argv[1])) {   
        printf("Could not open file...exiting.\n");   
        return 3;   
    }   

    // Display the image's dimensions to the end user.   
    printf("Width: %d  Height: %d  Depth: %d  Bpp: %d\n",   
           ilGetInteger(IL_IMAGE_WIDTH),   
           ilGetInteger(IL_IMAGE_HEIGHT),   
           ilGetInteger(IL_IMAGE_DEPTH),   
           ilGetInteger(IL_IMAGE_BYTES_PER_PIXEL));   

    return 0;
}

root@parallella:/home/parallella/parallella-examples/lena# make display
cc     display.c   -o display
/tmp/ccSqb23j.o: In function `main':
display.c:(.text+0xa): undefined reference to `ilInit'
display.c:(.text+0x16): undefined reference to `ilGenImages'
display.c:(.text+0x1e): undefined reference to `ilBindImage'
display.c:(.text+0x2a): undefined reference to `ilLoadImage'
display.c:(.text+0x48): undefined reference to `ilGetInteger'
display.c:(.text+0x52): undefined reference to `ilGetInteger'
display.c:(.text+0x5c): undefined reference to `ilGetInteger'
display.c:(.text+0x66): undefined reference to `ilGetInteger'
collect2: error: ld returned 1 exit status
make: *** [display] Error 1

How can I fix this linker problem?

Answer 1

Where are ilInit , ilGenImages , etc. defined? That is - which source file/pre-compiled library holds them? You need to provide that information to cc.

Assuming these are defined in a source file called foo.c , the solution will be:

cc display.c foo.c -o display

In further details, this error rises when the compiler has the correct declarations for your functions (in your header files), but no definition (actual binary or sources to create that binary) are found.