I had a working Makefile
for small C++ applications that just had a couple of source code files inside a single folder that was also the output folder. Now I am trying to separate source and object files and ran into a problem. This is how my makefile looks right now, I'll go into detail where the problem occurs below.
CC = gcc
CXX = g++
RM = del
TARGET = plox.exe
CFLAGS = -Wall -ggdb -O3 $(INCLUDE)
CXXFLAGS = -std=c++11 -Wall -ggdb -O3 $(INCLUDE)
LDFLAGS = $(LIB) -lglfw3 -lopengl32 -lglu32 -lgdi32
INCLUDE = -I$(GLFW_INC) -I$(GLAD_INC)
LIB = -L$(GLFW_LIB)
SRC_DIR = src
BUILD_DIR = build
GLFW_DIR = d:/external/glfw-3.1
GLFW_INC = $(GLFW)/include
GLFW_LIB = $(GLFW)/lib64
GLAD = d:/external/glad-c
GLAD_INC = $(GLAD)/include
CXX_SOURCES = $(SRC_DIR)/%.cpp
CXX_OBJS = $(addprefix $(BUILD_DIR)/, $(CXX_SOURCES:.cpp=.o))
OBJS = $(CXX_OBJS) $(BUILD_DIR)/glad.o
all: $(TARGET)
$(TARGET): $(OBJS)
$(CXX) -o $@ $^ $(LDFLAGS)
$(CXX_OBJS): %.o: $(SRC_DIR)%.cpp
$(CXX) $(CXXFLAGS) -c -o $@ $<
$(BUILD_DIR)/glad.o: src/glad.c
$(CC) -c $(CFLAGS) -c -o $(BUILD_DIR)/glad.o $(SRC_DIR)/glad.c
.PHONY: clean
clean:
$(RM) $(TARGET) $(OBJS)
The problem is in the line:
$(CXX_OBJS): %.o: $(SRC_DIR)/%.cpp
Before my changes, it looked like this:
$(CXX_OBJS): %.o: %.cpp
A friend helped gave me a template and I never really knew what that line really does. In another thread I learned that this is a static pattern rule so I guess this is where I made the mistake. But writing it down just now, I think the error could be earlier already. I might have made a mistake when defining $(CXX_OBJS)
. Could it be that the objects in that list are of the form build/src/test.o
instead of build/test.o
?
But how can I fix the addprefix
line to produce the correct output? And where does the error in the title come from; where am I mixing those? I thought it could be about the $(SRC_DIR)
in the static pattern rule because I probably misunderstood how it worked, but omitting it doesn't make the error go away. Moreover (assuming CXX_OBJS
is working correctly later), if the static pattern rule checks every file in the list $(CXX_OBJS)
for a match with %.o
, and then has a dependency on the same file with ending .cpp
, then that is also not correct because of the build
folder prefix.
All in all, I'm very confused about how to handle the folder prefixes correctly and any advice is greatly appreciated!
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