cmakefile

How to create and run a make file for C?

I have 3 files

hellomain.c
hellofunc.c
helloheader.h

and I am running via the GCC compiler. Usually I would type in:

gcc helloheader.h hellomain.c hellofunc.c -o results

And everything would run.

How could this be converted to a makefile? I know I have to title it makefile. I know I have to call it by typing in make in the compiler. But not sure what to actually type in the makefile.

Solution

  • Just about the simplest makefile possible for a project like your would be something like this:

    # The name of the source files
SOURCES = hellomain.c hellofunc.c

# The name of the executable
EXE = results

# Flags for compilation (adding warnings are always good)
CFLAGS = -Wall

# Flags for linking (none for the moment)
LDFLAGS =

# Libraries to link with (none for the moment)
LIBS =

# Use the GCC frontend program when linking
LD = gcc

# This creates a list of object files from the source files
OBJECTS = $(SOURCES:%.c=%.o)

# The first target, this will be the default target if none is specified
# This target tells "make" to make the "all" target
default: all

# Having an "all" target is customary, so one could write "make all"
# It depends on the executable program
all: $(EXE)

# This will link the executable from the object files
$(EXE): $(OBJECTS)
    $(LD) $(LDFLAGS) $(OBJECTS) -o  $(EXE) $(LIBS)

# This is a target that will compiler all needed source files into object files
# We don't need to specify a command or any rules, "make" will handle it automatically
%.o: %.c

# Target to clean up after us
clean:
    -rm -f $(EXE)      # Remove the executable file
    -rm -f $(OBJECTS)  # Remove the object files

# Finally we need to tell "make" what source and header file each object file depends on
hellomain.o: hellomain.c helloheader.h
hellofunc.o: hellofunc.c helloheader.h

    It could be even simpler, but with this you have some flexibility.

    Just for completeness sake, this is probably the most simple makefile possible:

    results: hellomain.c hellofunc.c helloheader.h
    $(CC) hellomain.c hellofunc.c -o results

    This is basically doing what you're already doing on the command-line. It's not very flexible and it will rebuild everything if any file changes.