使用Makefile实现增量编译报错的解决方案咨询

1. 目标目录子结构未创建：当前规则仅创建了BUILD_DIR顶层目录，生成子目录下的.obj文件时（如backend/backend.obj），对应的子目录不存在，导致make无法生成目标文件，触发"无规则"错误。
2. 缺少第三方依赖的编译规则：VENDORS中的源文件来自../include目录，原Makefile仅定义了../../src下cpp文件的编译规则，未处理第三方文件的编译逻辑。
3. BUILD_DIR路径不符合预期：原配置指向../../SIN2024/x64/Debug，与你预期的ROOT_DIR/build不符。

# Gather all the source files
SRC = $(wildcard ../../src/*.cpp ../../src/*/*.cpp ../../src/*/*/*.cpp ../../src/*/*/*/*.cpp)
VENDORS = $(wildcard ../include/glad/glad.c ../include/im3d/im3d.cpp ../include/imgui/*.cpp)

# Object files (stored in ROOT/build directory)
BUILD_DIR = ../../build
OBJ = $(SRC:../../src/%.cpp=$(BUILD_DIR)/%.obj) $(VENDORS:../include/%.cpp=$(BUILD_DIR)/%.obj) $(VENDORS:../include/%.c=$(BUILD_DIR)/%.obj)

# Include and library directories
INCLUDE = -I../include -I../../src
LIBS = -L../lib -lglfw3dll -lassimp

# Compiler and linker flags
CXX = g++
CXXFLAGS = -g --std=c++20 $(INCLUDE)
CC = gcc
CFLAGS = -g $(INCLUDE)

# Rule to generate object files from src directory cpp files
$(BUILD_DIR)/%.obj: ../../src/%.cpp
    @mkdir -p $(dir $@)
    $(CXX) $(CXXFLAGS) -c "$<" -o "$@"

# Rule to generate object files from include directory cpp files (third-party)
$(BUILD_DIR)/%.obj: ../include/%.cpp
    @mkdir -p $(dir $@)
    $(CXX) $(CXXFLAGS) -c "$<" -o "$@"

# Rule to generate object files from include directory c files (like glad.c)
$(BUILD_DIR)/%.obj: ../include/%.c
    @mkdir -p $(dir $@)
    $(CC) $(CFLAGS) -c "$<" -o "$@"

# Main build target
all: main.exe

# Rule to link the final executable
main.exe: $(OBJ)
    $(CXX) -o $@ $(OBJ) $(LIBS)

# Clean up object files and the executable
clean:
    rm -rf $(BUILD_DIR) main.exe

• 修正BUILD_DIR路径：改为../../build，匹配你预期的ROOT/build目录。
• 自动创建子目录：使用mkdir -p $(dir $@)替代mkdir -p $(BUILD_DIR)，$(dir $@)会自动提取目标文件所在的完整路径，确保所有子目录都被创建。
• 添加第三方文件编译规则：分别为../include下的cpp和c文件编写编译规则，覆盖所有VENDORS源文件的编译需求。
• 明确Windows可执行文件名：将链接目标改为main.exe，符合Windows平台的可执行文件命名规范。
• 优化VENDORS通配符：用../include/imgui/*.cpp简化重复的ImGui文件路径，提升维护性。

内容的提问来源于stack exchange，提问作者AstralHex