How can I modify my Makefile so that I build two different executables

Question

I have a Makefile that works correctly, but now I want to modify it so that I can build two different executables (i.e. client.exe, server.exe). In my directory, I have a client.cpp and a server.cpp, each of which has a main function. I know I can't build an executable with more than one main function. Ultimately, I want to be able to build an executable (client.exe or server.exe) using 'make client', 'make server', or something to that effect.

I have seen similar questions on this website, but all of the solutions I have seen assume that the number of source files will not change. Take for example this solution: Makefile to compile multiple C programs? Or this question: How can I configure my makefile for debug and release builds? I do not want to have to update my Makefile every time I add a new source file.

How can I modify my Makefile so that I build two different executables?

SRC_DIR := src
OBJ_DIR := obj
BIN_DIR := bin

EXE := $(BIN_DIR)/client.exe
SRC := $(wildcard $(SRC_DIR)/*.cpp)
OBJ := $(subst $(SRC_DIR),$(OBJ_DIR),$(SRC:.cpp=.o))
DEP := $(OBJ:.o=.d)

.PHONY: clean

all: $(EXE)

CXX      := g++
CPPFLAGS := -I$(PWD) -MMD -MP
CXXFLAGS := -std=c++17
LDFLAGS  := -L /usr/lib/x86_64-linux-gnu
CFLAGS   := -Wall

$(EXE): $(OBJ) | $(BIN_DIR)
    $(CXX) $(LDFLAGS) $^ -o $@

$(OBJ_DIR)/%.o: $(SRC_DIR)/%.cpp | $(OBJ_DIR)
    $(CXX) $(CPPFLAGS) $(CFLAGS) $(CXXFLAGS) -c $< -o $@

$(BIN_DIR) $(OBJ_DIR):
    mkdir -p $@

clean:
    @$(RM) -rv $(BIN_DIR) $(OBJ_DIR)

-include $(DEP)

I have tried to exclude either the client.cpp or server.cpp file depending on which command I use (e.g. 'make client' or 'make server'). But I reached a dead end since I don't know how to make a rule that excludes one file.

SRC := $(filter-out $(SRC_DIR)/client.cpp, $(wildcard $(SRC_DIR)/*.cpp))
SRC := $(filter-out $(SRC_DIR)/server.cpp, $(wildcard $(SRC_DIR)/*.cpp))

Renaud Pacalet · Accepted Answer · 2022-04-13T08:11:52.850

Simply build two different lists of object files for your two executables:

...
EXE := $(patsubst %,$(BIN_DIR)/%.exe,client server)
...
CLIENT_OBJ := $(filter-out $(OBJ_DIR)/server.o,$(OBJ))
SERVER_OBJ := $(filter-out $(OBJ_DIR)/client.o,$(OBJ))

.PHONY: all client server

all: $(EXE)
client: $(BIN_DIR)/client.exe
server: $(BIN_DIR)/server.exe

$(BIN_DIR)/client.exe: $(CLIENT_OBJ)
$(BIN_DIR)/server.exe: $(SERVER_OBJ)

$(EXE): | $(BIN_DIR)
    $(CXX) $(LDFLAGS) $^ -o $@
...

How can I modify my Makefile so that I build two different executables

1 Answers1