make -C tests
make[1]: Entering directory '/home/marko/projects/preeny/preeny/tests'
cc hello.c -o hello
hello.c: In function ‘main’:
hello.c:3:2: warning: implicit declaration of function ‘puts’ [-Wimplicit-function-declaration]
puts("Hello world!");
^
make[1]: Leaving directory '/home/marko/projects/preeny/preeny/tests'
> gcc --version
gcc (GCC) 5.1.1 20150618 (Red Hat 5.1.1-4)
Fix for this: