usr/bin/ld: cannot find -l<nameOfTheLibrary>
To figure out what the linker is looking for, run it in verbose mode.
For example, I encountered this issue while trying to compile MySQL with ZLIB support. I was receiving an error like this during compilation:
/usr/bin/ld: cannot find -lzlib
I did some Googl'ing and kept coming across different issues of the same kind where people would say to make sure the .so file actually exists and if it doesn't, then create a symlink to the versioned file, for example, zlib.so.1.2.8. But, when I checked, zlib.so DID exist. So, I thought, surely that couldn't be the problem.
I came across another post on the Internets that suggested to run make with LD_DEBUG=all:
LD_DEBUG=all make
Although I got a TON of debugging output, it wasn't actually helpful. It added more confusion than anything else. So, I was about to give up.
Then, I had an epiphany. I thought to actually check the help text for the ld command:
ld --help
From that, I figured out how to run ld in verbose mode (imagine that):
ld -lzlib --verbose
This is the output I got:
==================================================
attempt to open /usr/x86_64-linux-gnu/lib64/libzlib.so failed
attempt to open /usr/x86_64-linux-gnu/lib64/libzlib.a failed
attempt to open /usr/local/lib64/libzlib.so failed
attempt to open /usr/local/lib64/libzlib.a failed
attempt to open /lib64/libzlib.so failed
attempt to open /lib64/libzlib.a failed
attempt to open /usr/lib64/libzlib.so failed
attempt to open /usr/lib64/libzlib.a failed
attempt to open /usr/x86_64-linux-gnu/lib/libzlib.so failed
attempt to open /usr/x86_64-linux-gnu/lib/libzlib.a failed
attempt to open /usr/local/lib/libzlib.so failed
attempt to open /usr/local/lib/libzlib.a failed
attempt to open /lib/libzlib.so failed
attempt to open /lib/libzlib.a failed
attempt to open /usr/lib/libzlib.so failed
attempt to open /usr/lib/libzlib.a failed
/usr/bin/ld.bfd.real: cannot find -lzlib
Ding, ding, ding...
So, to finally fix it so I could compile MySQL with my own version of ZLIB (rather than the bundled version):
sudo ln -s /usr/lib/libz.so.1.2.8 /usr/lib/libzlib.so
Voila!
If your library name is say libxyz.so and it is located on path say:
/home/user/myDir
then to link it to your program:
g++ -L/home/user/myDir -lxyz myprog.cpp -o myprog
There does not seem to be any answer which addresses the very common beginner problem of failing to install the required library in the first place.
On Debianish platforms, if libfoo is missing, you can frequently install it with something like
apt-get install libfoo-dev
The -dev version of the package is required for development work, even trivial development work such as compiling source code to link to the library.
The package name will sometimes require some decorations (libfoo0-dev? foo-dev without the lib prefix? etc), or you can simply use your distro's package search to find out precisely which packages provide a particular file.
(If there is more than one, you will need to find out what their differences are. Picking the coolest or the most popular is a common shortcut, but not an acceptable procedure for any serious development work.)
For other architectures (most notably RPM) similar procedures apply, though the details will be different.