ld cannot find an existing library

 am attempting to link an application with g++ on this Debian lenny system. ld is complaining it cannot find specified libraries. The specific example here is ImageMagick, but I am having similar problems with a few other libraries too.

I am calling the linker with:

g++ -w (..lots of .o files/include directories/etc..) \ -L/usr/lib -lmagic 

ld complains:

/usr/bin/ld: cannot find -lmagic 

However, libmagic exists:

$ locate libmagic.so /usr/lib/libmagic.so.1 /usr/lib/libmagic.so.1.0.0 $ ls -all /usr/lib/libmagic.so.1* lrwxrwxrwx 1 root root    17 2008-12-01 03:52 /usr/lib/libmagic.so.1 -> libmagic.so.1.0.0 -rwxrwxrwx 1 root root 84664 2008-09-09 00:05 /usr/lib/libmagic.so.1.0.0 $ ldd /usr/lib/libmagic.so.1.0.0      linux-gate.so.1 =>  (0xb7f85000)     libz.so.1 => /usr/lib/libz.so.1 (0xb7f51000)     libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb7df6000)     /lib/ld-linux.so.2 (0xb7f86000) $ sudo ldconfig -v | grep "libmagic"     libmagic.so.1 -> libmagic.so.1.0.0 

How do I diagnose this problem further, and what could be wrong? Am I doing something completely stupid?

 

The problem is the linker is looking for libmagic.so but you only have libmagic.so.1

A quick hack is to symlink libmagic.so.1 to libmagic.so

 

 

that works, I am kind of perplexed that it would name the file in a completely useless way by default - can you provide any insight why it would do this by default? – maxpenguin
Dec 3 '08 at 1:09 

Most likely it is a misconfiguration of the install script – grepsedawk
Dec 3 '08 at 1:15 

The foo.so.1 is a symlink to foo.so.1.0.0 too. This way, you can have several versions of a library in your system, and if an application needs a specific one, it can link to it, while in general, the newest one is chosen by
symlink. I do not know why this symlink was missing. – Svante
Dec 3 '08 at 1:19 

libmagic.so.1 is the soname, used by the dynamic linker; libmagic.so is used by the linker, and is usually together with the headers in the -dev package. The symlink might be missing because the -dev package was not installed.
– CesarB
Dec 3 '08 at 10:49