ld cannot find an existing library

Question

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 - gt  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   gt    0xb7f85000      libz so 1   gt   usr lib libz so 1  0xb7f51000      libc so 6   gt   lib i686 cmov libc so 6  0xb7df6000       lib ld-linux so 2  0xb7f86000    sudo ldconfig -v   grep  libmagic      libmagic so 1 - gt  libmagic so 1 0 0   How do I diagnose this problem further  and what could be wrong  Am I doing something completely stupid

User · Answer

It is Debian convention to separate shared libraries into their runtime components (libmagic1: /usr/lib/libmagic.so.1 ? libmagic.so.1.0.0) and their development components (libmagic-dev: /usr/lib/libmagic.so ? …).

Because the library's soname is libmagic.so.1, that's the string that gets embedded into the executable so that's the file that is loaded when the executable is run.

However, because the library is specified as -lmagic to the linker, it looks for libmagic.so, which is why it is needed for development.

See Diego E. Pettenò: Linkers and names for details on how this all works on Linux.

In short, you should apt-get install libmagic-dev. This will not only give you libmagic.so but also other files necessary for compiling like /usr/include/magic.h.

User · Answer

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

User · Answer

Installing libgl1-mesa-dev from the Ubuntu repo resolved this problem for me

User · Answer

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

User · Answer

In Ubuntu  you can install libtool which resolves the libraries automatically     sudo apt-get install libtool   This resolved a problem with ltdl for me  which had been installed as libltdl so 7 and wasn t found as simply -lltdl in the make

User · Answer

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

User · Answer

Installing libgl1-mesa-dev from the Ubuntu repo resolved this problem for me

User · Answer

It is Debian convention to separate shared libraries into their runtime components (libmagic1: /usr/lib/libmagic.so.1 ? libmagic.so.1.0.0) and their development components (libmagic-dev: /usr/lib/libmagic.so ? …).

Because the library's soname is libmagic.so.1, that's the string that gets embedded into the executable so that's the file that is loaded when the executable is run.

However, because the library is specified as -lmagic to the linker, it looks for libmagic.so, which is why it is needed for development.

See Diego E. Pettenò: Linkers and names for details on how this all works on Linux.

In short, you should apt-get install libmagic-dev. This will not only give you libmagic.so but also other files necessary for compiling like /usr/include/magic.h.

User · Answer

In Ubuntu  you can install libtool which resolves the libraries automatically     sudo apt-get install libtool   This resolved a problem with ltdl for me  which had been installed as libltdl so 7 and wasn t found as simply -lltdl in the make

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

As mentioned above the linker is looking for libmagic so  but you only have libmagic so 1   To solve this problem just perform an update cache    ldconfig -v    To verify you can run     ldconfig -p   grep libmagic

User · Answer

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

User · Answer

As mentioned above the linker is looking for libmagic so  but you only have libmagic so 1   To solve this problem just perform an update cache    ldconfig -v    To verify you can run     ldconfig -p   grep libmagic

User · Answer

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

User · Answer

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

User · Answer

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

[linux] ld cannot find an existing library

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