Nauty and Traces on Mac OS X - c

Question

I am trying to use the code Nauty and Traces http://pallini.di.uniroma1.it/. But when I complied an example, say nautyex8.c (provided by the package), the following error showed up:
Undefined symbols for architecture x86_64:
"_alloc_error", referenced from:
_main in nautyex8-54d9da.o
"_densenauty", referenced from:
_main in nautyex8-54d9da.o
"_dispatch_graph", referenced from:
_main.options in nautyex8-54d9da.o
"_nauty_check", referenced from:
_main in nautyex8-54d9da.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I am using Mac OS X Yosemite (10.10.5) and Xcode (version 7.1). I believe that there is no error in the codes because they are widely used so I guess the problem comes from my system settings.
Thank you so much!

Answer 1

I've just opened a pull request to make brew install nauty work on OS X: https://github.com/Homebrew/homebrew-core/pull/48701
Until then, here's how you would build nautyex8.c on OS X, as of Nauty/Traces 2.6r12.
Step 1 is to download the code and build the library:
wget http://pallini.di.uniroma1.it/nauty26r12.tar.gz
tar zxvf nauty26r12.tar.gz
cd nauty26r12
./configure
make
ls -l nauty.a
Step 2 is to compile nautyex8.c and link it against the library you just built:
gcc -O3 nautyex8.c nauty.a
./a.out
You probably forgot to put that "nauty.a" at the end of your compiler command line. If I do that too, I get:
gcc -O3 nautyex8.c
Undefined symbols for architecture x86_64:
"_alloc_error", referenced from:
_main in nautyex8-05f086.o
"_densenauty", referenced from:
_main in nautyex8-05f086.o
"_dispatch_graph", referenced from:
_main.options in nautyex8-05f086.o
"_nauty_check", referenced from:
_main in nautyex8-05f086.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
which exactly matches the symptom you described.