How to create multiple executables using makefile from a single target - build

Question

I am trying to build excutables for multiple files which are built in the same way. When i run make all the excutables should be generated. I am getting error at prerequisites part of the macro.
CXX = g++
CXX_FLAGS = -g -Wall
LD_FLAGS =
INC_DIR = -I/my/path/include
SRC_DIR = .
LIB_DIR = -L$/my/path/lib
OBJ_DIR = obj
EXE_DIR = exe
SRCS := $(foreach s_dir, $(SRC_DIR), $(wildcard $(s_dir)/*.cpp))
OBJS := $(patsubst $(SRC_DIR)/%.cpp, $(OBJ_DIR)/%.o, $(SRCS))
EXES := $(patsubst $(SRC_DIR)/%.cpp, $(EXE_DIR)/%.out, $(SRCS))
all: create_directories create_objects create_exes
create_directories:
#echo "Creating $(OBJ_DIR) and $(EXE_DIR)..."
#mkdir -p obj
#mkdir -p exe
create_objects:
$(foreach b_dir, $(OBJ_DIR), $(eval $(call build-objects, $(b_dir))))
create_exes:
$(foreach ot, $(EXE_DIR), $(eval $(call build-exes, $(ot))))
define build-objects
$1/%.o: %.cpp
$(CXX) $(CXX_FLAGS) $(INC_DIR) -MMD -MP -c $$< -o $$#
endef
define build-exes
$1/%.out:obj/%.o
$(CXX) $(LD_FLAGS) -o $# $(OBJS) $(LIB_DIR) -lmylib
endef
Is this a right way to do generate multiple exes or any other simple way?

Answer 1

If I'm reading this makefile right, then it's much too complicated.
First let's have a rule to build object files:
$(OBJ_DIR)/%.o: %.cpp
$(CXX) $(CXX_FLAGS) $(INC_DIR) -MMD -MP -c $< -o $#
Now if we're not sure about the existence of obj/, we could add a rule to create it, but for the moment let's just put in a failsafe (we'll come back to this later):
$(OBJ_DIR)/%.o: %.cpp
#mkdir -p $(OBJ_DIR)
$(CXX) $(CXX_FLAGS) $(INC_DIR) -MMD -MP -c $< -o $#
And a similar rule to build the executables:
$(EXE_DIR)/%.out: $(OBJ_DIR)/%.o
#mkdir -p $(EXE_DIR)
$(CXX) $(LD_FLAGS) -o $# $^ $(LIB_DIR) -lmylib
And finally (at the top) some variables, the lists of files, and the all rule:
CXX = g++
CXX_FLAGS = -g -Wall
LD_FLAGS =
INC_DIR = -I/my/path/include
SRC_DIR = .
LIB_DIR = -L$/my/path/lib
OBJ_DIR = obj
EXE_DIR = exe
SRCS := $(wildcard $(SRC_DIR)/*.cpp)
EXES := $(patsubst $(SRC_DIR)/%.cpp, $(EXE_DIR)/%.out, $(SRCS))
# Let the object files take care of themselves
all: $(EXES)
That's all you need. Once this is working perfectly, we can discuss refinements like rules for building directories.