Make recompiles non modified files - c++

Question

I have a makefile for my program but I got everything recompiled every time I run it, even if I modify nothing.
Every time I run make it recompiles simHwIntf.cpp showHelp.cpp and sendFromFile.cpp
This is my make file:
IDIR = inc
LDIR = -L/usr/lib/x86_64-linux-gnu/
SDIR = src
ODIR = obj
BINDIR = bin
LDLIBS = -luhd
OBJ = $(patsubst %,$(ODIR)/%,$(O_FILES))
CC = g++
CFLAGS = -Wall -std=c++11 -I $(IDIR) #-Werror
BINARIES= main
C_FILES = simHwIntf.cpp showHelp.cpp sendFromFile.cpp
H_FILES = simHwIntf.h
O_FILES = $(C_FILES:.cpp=.o)
all: $(BINARIES)
#echo "Make file executed"
$(BINARIES): $(O_FILES)
$(CC) $(CFLAGS) -o $(BINDIR)/$# $(OBJ) $(LDIR) $(LDLIBS)
fileCreator: fileCreator.o
$(CC) $(CFLAGS) -o $(BINDIR)/$# $(ODIR)/fileCreator.o
fileHandler: fileHandler.o
$(CC) $(CFLAGS) -o $(BINDIR)/$# $(ODIR)/fileHandler.o
backYard: backYard.o
$(CC) $(CFLAGS) -o $(BINDIR)/$# $(ODIR)/backYard.o
%.o: $(SDIR)/%.cpp $(IDIR)/$(H_FILES)
$(CC) $(CFLAGS) -c -o $(ODIR)/$# $<
clean:
-rm -rf $(ODIR)/*.o *~
distclean: clean
-rm -rf $(BINDIR)/*
Each time the output in the shell is:
g++ -Wall -std=c++11 -I inc -c -o obj/simHwIntf.o src/simHwIntf.cpp
g++ -Wall -std=c++11 -I inc -c -o obj/showHelp.o src/showHelp.cpp
g++ -Wall -std=c++11 -I inc -c -o obj/sendFromFile.o src/sendFromFile.cpp
g++ -Wall -std=c++11 -I inc -o bin/main obj/simHwIntf.o obj/showHelp.o obj/sendFromFile.o -L/usr/lib/x86_64-linux-gnu/ -luhd
Make file executed
I've already search and read this: (How do I make Makefile to recompile only changed files?) but didn't help much.
Anybody that could give me a hand with this ?
I have a doubt with the directories, maybe one or several directories are re-created each time I run make and this causes everything inside to look like new to the compiler.
Thanks

Answer 1

You can see what triggered the build by echoing the dependencies that changed. Add this to your %.o target :
#echo [triggered by changes in $?]
You should also use the VPATH special variable instead of specifying the sources path in your %.o target. See GNU make VPATH documentation

Answer 2

Please try replacing
%.o: $(SDIR)/%.cpp $(IDIR)/$(H_FILES)
$(CC) $(CFLAGS) -c -o $(ODIR)/$# $<
with
$(ODIR)/%.o: $(SDIR)/%.cpp $(IDIR)/$(H_FILES)
$(CC) $(CFLAGS) -c -o $(ODIR)/$# $<

Answer 3

Directories matter when you define targets.
If a define a rule
myexec: objdir/myexec.o
$(CC) $(CFLAGS) -o bindir/myexec objdir/myexec.o $(LDFLAGS)
Make believes that that this would create the file myexec in the working directory. When you rerun make the target myexec wasn't found, so it will be created again. Add the paths in the targets and it should work.
Try replacing
BINARIES= main
with
BINARIES= $(BINDIR)/main
and the rule
$(CC) $(CFLAGS) -o $(BINDIR)/$# $(OBJ) $(LDIR) $(LDLIBS)
with
$(CC) $(CFLAGS) -o $# $^ $(LDIR) $(LDLIBS)
And change the other rules similarly.
Note, in general it is a bad idea to use $# in combination with a path when creating the target in some rule (as in $(BINDIR)/$#), because this will never create the actual target file. A bare $# should be sufficient.