Question

“I get an error when I try to my application with a make file. This is my first attempt at creating a make file myself and i found many examples online, but i cannot get mine to work. The error i get, however is a compile error, that what i compile manually, i do not get. The error is:

`dave@ubuntu:~/School/CS647/Programs/Homework4$ make
g++ -Wall -o StatWrapper StatWrapper.o tools.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
make: *** [StatWrapper] Error 1

`
Here is my make file:

CC = g++
CFLAGS = -Wall
UTILDIR = ../../Utilities/
OBJECTS =  Sweeper.o FileID.o P4Ford.o DirentWrapper.o StatWrapper.o tools.o

all: StatWrapper DirentWrapper FileID Sweeper P4Ford

#P4Ford: $(OBJECTS)
#   $(CC) $(OBJECTS) -o P4Ford

DirentWrapper: DirentWrapper.o tools.o
    $(CC) $(CFLAGS) -o DirentWrapper DirentWrapper.o tools.o

StatWrapper: StatWrapper.o tools.o
    $(CC) $(CFLAGS) -o StatWrapper StatWrapper.o tools.o

P4Ford: P4Ford.o Sweeper.o
    $(CC) $(CFLAGS) -o P4Ford P4Ford.o Sweeper.o

Sweeper: Sweeper.o FileID.o StatWrapper.o DirentWrapper.o tools.o
    $(CC) $(CFLAGS) -o Sweeper Sweeper.o FileID.o StatWrapper.o DirentWrapper.o tools.o

FileID: FileID.o tools.o
    $(CC) $(CFLAGS) -o FileID FileID.o tools.o

#tools: tools.o
#   $(CC) $(CFLAGS) $(UTILDIR)tools.cpp

# dependencies ---------------------------------------------------
DirentWrapper.o: $(UTILDIR)DirentWrapper.cpp  $(UTILDIR)DirentWrapper.hpp
StatWrapper.o: $(UTILDIR)StatWrapper.cpp  $(UTILDIR)StatWrapper.hpp
P4Ford.o: P4Ford.cpp  Sweeper.hpp
Sweeper.o: Sweeper.cpp  FileID.hpp
FileID.o: FileID.cpp  $(UTILDIR)tools.hpp
tools.o: $(UTILDIR)tools.cpp $(UTILDIR)tools.hpp

# cleanup
clean:
    rm -f $(OBJECTS)

I believe this is an issue with my make file because it works when i compile manually, but i can’t be sure.

Thanks in advance.

Answer 1

Just add -c to the rules building object files. Without this the compiler assumes you are creating an executable which requires main() to be defined. The -c flag indicates the no linking shall be done, yet.