prepare (1/3): 
finished

make (2/3): 
g++ -o main main.cpp comparison.cpp
/tmp/ccVkT85M.o: In function `mergeSort(int*, long, long)':
comparison.cpp:(.text+0x349): undefined reference to `merge(int*, long, long, long)'
collect2: error: ld returned 1 exit status
Makefile:2: recipe for target 'all' failed
make: *** [all] Error 1

build failed