ld cannot find an existing library

maxpenguin_10733 0
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I 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?

shared-objects shared-libraries linker gcc linux
8 Answers

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

grepsedawk_143880

As just formulated by grepsedawk, the answer lies in the -l option of g++, calling ld. If you look at the man page of this command, you can either do:

  • g++ -l:libmagic.so.1 [...]
  • or: g++ -lmagic [...] , if you have a symlink named libmagic.so in your libs path
Piotr_Lesnicki_387960

Unless I'm badly mistaken libmagic or -lmagic is not the same library as ImageMagick. You state that you want ImageMagick.

ImageMagick comes with a utility to supply all appropriate options to the compiler.

Ex:

g++ program.cpp `Magick++-config --cppflags --cxxflags --ldflags --libs` -o "prog"
Brian_Gianforcaro_34150

I tried all solutions mentioned above but none of them solved my issue but finally I solved it with the following command.

sudo apt-get install libgmp3-dev

This will do the magic.

user_163967720
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