I am new to makefiles. I learned makefile creation and other related concepts from "Managing projects with GNU make" book. The makefile is ready now and I need to make sure the one which I created is OK. Here is the makefile
#Main makefile which does the build
#makedepend flags
DFLAGS =
#Compiler flags
#if mode variable is empty, setting debug build mode
ifeq ($(mode),release)
CFLAGS = -Wall
else
mode = debug
CFLAGS = -g -Wall
endif
CC = g++
PROG = fooexe
#each module will append the source files to here
SRC := main.cpp
#including the description
include bar/module.mk
include foo/module.mk
OBJ := $(patsubst %.cpp, %.o, $(filter %.cpp,$(SRC)))
.PHONY:all
all: information fooexe
information:
ifneq ($(mode),release)
ifneq ($(mode),debug)
@echo "Invalid build mode."
@echo "Please use 'make mode=release' or 'make mode=debug'"
@exit 1
endif
endif
@echo "Building on "$(mode)" mode"
@echo ".........................."
#linking the program
fooexe: $(OBJ)
$(CC) -o $(PROG) $(OBJ)
%.o:%.cpp
$(CC) $(CFLAGS) -c $< -o $@
depend:
makedepend -- $(DFLAGS) -- $(SRC)
.PHONY:clean
clean:
find . -name "*.o" | xargs rm -vf
rm -vf fooexe
Questions
- The above given makefile works well with release and debug builds. But is it in the correct format? Or do you see any flaws in that?
- Above makefile does debug build by default when invoked using make. For release builds, make mode=release is required. Is this the correct approach?
- Is the debug and release compiler flags supplied to g++ is correct? For debug, I use -g -Wall and for release, just -Wall. Is this right?
Any help would be great.
Best Answer
-g
flag for the release build is not automatically bad, but if your code ever produces a core dump, it is easier to make head or tail of the core dump if the program file includes debugging information. The primary cost of debugging information is extra sections in the program file that do not need to be loaded into system memory - the runtime cost is small.-g
and-O
. It is harder to debug optimized code, but it gives you (often significant) performance benefits.