Make recompiles non modified files

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