I am trying to practice to create Makefiles. The goal is to create a makefile such that if a change is made to any of the source code files, the project can be rebuilt by typing make at the command line.
I have the following files:
Code:
ac.cc: has include ac.h and pg.h
fr.cc: has main function and include pg.h
gq.cc: has main function and include ac.h, bb.h
pg.cc: has include pg.h
vw.cc: has main function and include ac.h
This is the error I keep getting:
Code:
Makefile:32: warning: overriding recipe for target 'pg.o'
Makefile:8: warning: ignoring old recipe for target 'pg.o'
g++ -c ac.cc
g++ -c pg.cc
g++ -o acprog ac.o pg.o
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crt1.o: In function `_start':
/build/glibc-Ir_s5K/glibc-2.19/csu/../sysdeps/x86_64/start.S:118: undefined reference to `main'
collect2: error: ld returned 1 exit status
Makefile:2: recipe for target 'acprog' failed
make: *** [acprog] Error 1
z1755294@hopper:~/assign1/assign1$
What exactly am I doing wrong and how can I fix this to make it work.
Thanks
Moderator's Comments:
Please use CODE or ICODE tags for all sample input, output, and code segments. And use CODE tags (not ICODE tags) for full line and multiline input, output, and code segments.
The warnings at the start of your output are there because you have two rules in your make file for building pg.o (both shown in red above). Since you said that pg.cc includes pg.h (but not ac.h), get rid of the first rule in your makefile for building pg.o that starts on line 8 in your makefile.
All runnable C++ programs must include one function named main() (which is the function that will be called when your program starts execution). Your build is failing because neither pg.cc nor ac.cc contain such a function.
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