Basic Makefile with two .cpp files and a header file - c++

Question

I wanted to learn how to create a basic Makefile for my program containing 3 files: a.cpp, b.cpp, and b.h. I include b.h in a.cpp and call a function that is declared there and defined in b.cpp. I went through several Makefile tutorials and came up with a Makefile like this:
CC=g++
CFLAGS= -std=c++11 -Wall -pedantic -g
SOURCES= a.cpp b.cpp
DEPS= b.h
OBJECTS=$(SOURCES:.cpp=.o)
EXECUTABLE=exec
all: $(EXECUTABLE)
#echo Make has finished.
$(EXECUTABLE): $(OBJECTS)
$(CC) $(CFLAGS) $(OBJECTS) -o $(EXECUTABLE)
%.o: %.cpp $(DEPS)
$(CC) $(CFLAGS) -c -o $# $<
clean:
$(RM) *.o *~ $(EXECUTABLE)
However, when I make and run exec it doesn't work as intended. The compiler gives no warnings or errors, but the function call in a.cpp is skipped over as if it's not there. Instead if I run the simple
g++ -std=c++11 -Wall -pedantic -g a.cpp b.cpp -o exec
my program runs as intended. Obviously I'm not doing something right in my Makefile, but I cannot figure out what.

Answer 1

CC=g++
CFLAGS= -std=c++11 -Wall -pedantic -g
SOURCES= a.cpp b.cpp
DEPS= b.h
OBJECTS=$(SOURCES:.cpp=.o)
EXECUTABLE=exec
all: $(EXECUTABLE)
#echo Make has finished.
$(EXECUTABLE): $(OBJECTS)
$(CC) $(OBJECTS) -o $#
.cpp.o:
$(CC) $(CFLAGS) -c $*.cpp
clean:
$(RM) *.o *~ $(EXECUTABLE)

Answer 2

When reading your Makefile example, it's useful to read it as a computer would, replacing fields as you walk through the file. The lines that popped out to me were:
SOURCES= a.cpp b.cpp
...
OBJECTS=$(SOURCES:.cpp=.o)
...
$(EXECUTABLE): $(OBJECTS)
$(CC) $(CFLAGS) $(OBJECTS) -o $(EXECUTABLE)
...
%.o: %.cpp $(DEPS)
$(CC) $(CFLAGS) -c -o $# $<
The first line defines the source files. The second defines the object files (extension .o) that the Makefile says can be built from the .cpp files. The third and fourth define a rule to produce the final executable, which requires that your two object files, a.o and b.o be successfully generated. The last two lines define a rule for generation of the object files, which specifies that they require their same-name .cpp files and the $(DEPS) == b.h files.
In the end, this Makefile calls the following lines:
g++ -std=c++11 -Wall -pedantic -g -c -o a.o a.cpp b.h
g++ -std=c++11 -Wall -pedantic -g -c -o b.o b.cpp b.h
g++ -std=c++11 -Wall -pedantic -g a.o b.o -o exec
So it appears that the breakage in your code is in the mixed-up flags passed to the compiler the first two times.