eos$ make Makefile; make
make: Warning: File `Makefile' has modification time 6.1 s in the future
make: Nothing to be done for `Makefile'.
make: warning:  Clock skew detected.  Your build may be incomplete.
make: Warning: File `Makefile' has modification time 6.1 s in the future
gcc -Wall -std=c99   -c -o writer.o writer.c
gcc -Wall -std=c99   -c -o reader.o reader.c
gcc -Wall -std=c99 writer.o reader.o -o main
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
make: *** [main] Error 1