如何在使用 g++ 和 gcc 编译 obj 文件的 Makefile 中避免循环依赖？

Question

I tried to create a makefile for a project that use c++ and c. I need to compile those file in order to make de .o file, but when I compile using make I have circular dependency that is dropped.

I don't know why this error occurs as I tried to separate the building of .o files that comes from .c and .o files that comes froms .cpp files.

Here is my makefile :

SRC = $(wildcard *.c)
SRC++ = $(wildcard *.cpp)
OBJ = $(SRC++:.cpp=.o) $(SRC:.c=.o)
DEP = $(SRC:.c=.d) $(SRC++:.cpp=.d)

CC=gcc
CXX=g++

CFLAGS = -Wall
CXXFLAGS = -Wall

all: $(OBJ)

%.c : %.o
    $(CC) -c $(CFLAGS) $< -o $@  

%.cpp : %.o
    $(CXX) -c $(CXXFLAGS) $< -o $@  

# Clean the project
clean:
    @rm -f $(OBJ) $(DEP)

-include $(DEP)

Do you have any idea of what I am doing wrong ?

Answer 1

The rules you wrote are %.cpp : %.o and %.c : %.o . You wrote those rules the wrong way around. The target being built must be to the left of the colon, and the things it depends on must be to the right.

The error message tells you about a circular dependency because GNU Make defines an implicit rule where the dependencies are defined in the correct direction.