Make did not work after I changed my file - makefile

Question

These are my files:
add.c add.h main.c makefile
This is makefile:
main:main.o add.o
gcc -o main main.o add.o
main.o:$(#:%.o=%.c)
gcc -o main.o -c main.c
add.o:$(#:%.o=%.c) $(#:%.o=%.h)
gcc -o add.o -c add.c
.PHONY:clean
clean:
rm *.o -rf
rm main -rf
Then after I change the main.c and make.
But make told me this:
make: `main' is up to date.
If I change my makefile:
main:main.o add.o
gcc -o main main.o add.o
main.o:main.c
gcc -o main.o -c main.c
add.o:$(#:%.o=%.c) $(#:%.o=%.h)
gcc -o add.o -c add.c
.PHONY:clean
clean:
rm *.o -rf
rm main -rf
Then after I change the main.c and make.
It can work.
I donot know the reason.

Answer 1

The dependencies in
main.o:$(#:%.o=%.c)
add.o:$(#:%.o=%.c) $(#:%.o=%.h)
are not valid make syntax.
Replace these two rules with one pattern (generic) rule:
%.o : %.c
gcc -c -o $# ${CPPFLAGS} ${CFLAGS} $<
The above rule is actually very similar to the built-in rule for compiling .o files from .c:
Compiling C programs
n.o is made automatically from n.c with a recipe of the form $(CC) $(CPPFLAGS) $(CFLAGS) -c.
In other words, you can remove your original rules for main.o and add.o and it should build correctly.