Library Dependencies

• One library will often depend on another library. For example, many GNU/Linux systems include libtiff, a library that contains functions for reading and writing image files in the TIFF format.This library, in turn, uses the libraries libjpeg (JPEG image routines) and libz (compression routines).

  #include <stdio.h>
  #include <tiffio.h>
  
  int main (int argc, char** argv)
  {
    TIFF* tiff;
    tiff = TIFFOpen (argv[1], "r");
    TIFFClose (tiff);
    return 0;
  }
  $ gcc -o tifftest tifftest.c -ltiff
  $ ldd tifftest
  libtiff.so.3 => /usr/lib/libtiff.so.3 (0x4001d000)
  libc.so.6 => /lib/libc.so.6 (0x40060000)
  libjpeg.so.62 => /usr/lib/libjpeg.so.62 (0x40155000)
  libz.so.1 => /usr/lib/libz.so.1 (0x40174000)
  /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
  

• Static libraries, on the other hand, cannot point to other libraries. If decide to link with the static version of libtiff by specifying $-static$ on your command line, you will encounter unresolved symbols:

  $ gcc -static -o tifftest tifftest.c -ltiff
  /usr/bin/../lib/libtiff.a(tif_jpeg.o): In function 'TIFFjpeg_error_exit':
  tif_jpeg.o(.text+0x2a): undefined reference to 'jpeg_abort'
  /usr/bin/../lib/libtiff.a(tif_jpeg.o): In function 'TIFFjpeg_create_compress':
  tif_jpeg.o(.text+0x8d): undefined reference to 'jpeg_std_error'
  tif_jpeg.o(.text+0xcf): undefined reference to 'jpeg_CreateCompress'
  ...
  

  To link this program statically, you must specify the other two libraries yourself:

  $ gcc -static -o tifftest tifftest.c -ltiff -ljpeg -lz