当所有cpp文件在一个目录中时,这个makefile工作得很好。但是在创建子目录后,由于缺少子目录,它无法创建*.o文件:
目录结构
.
├── Makefile
├── README.md
├── src
│ ├── Adventurer
│ │ └── Adventurer.cpp
│ ├── Board
│ │ ├── AdventureTile.cpp
│ │ └── Board.cpp
Makefile
CC := g++ # This is the main compiler
SRCDIR := src
BUILDDIR := build
TARGET := bin/forbidden-island
SRCEXT := cpp
SOURCES := $(shell find $(SRCDIR) -type f -name *.$(SRCEXT))
OBJECTS := $(patsubst $(SRCDIR)/%,$(BUILDDIR)/%,$(SOURCES:.$(SRCEXT)=.o))
CFLAGS := -g -Wall
LIB := -lsfml-graphics -lsfml-window -lsfml-system
INC := -I include
$(BUILDDIR)/%.o: $(SRCDIR)/%.$(SRCEXT)
# BUILDPATH=$($(BUILDDIR)/%.o) # missing step of creating subdirectories
# OFILE=$(basename $@)
@mkdir -p $(BUILDDIR)
@echo " $(CC) $(CFLAGS) $(INC) -c -o $@ $<"; $(CC) $(CFLAGS) $(INC) -c -o $@ $<
这段代码的一个示例输出如下:
g++ -g -Wall -I include -c -o build/Board/Board.o src/Board/Board.cpp
src/Board/Board.cpp: In member function ‘AdventureTile Board::getTile(int, int)’:
src/Board/Board.cpp:13:1: warning: no return statement in function returning non-void [-Wreturn-type]
}
^
Assembler messages:
Fatal error: can't create build/Board/Board.o: No such file or directory
Makefile:23: recipe for target 'build/Board/Board.o' failed
make: *** [build/Board/Board.o] Error 1
如何更改命令,使其只是o文件的名称而不是完整路径。使用特殊变量$@。
(basename $@)
返回了build/Board/Board
,但需要它是board.o。
=============== 解决方案 ===============
Makefile失败是因为子目录没有创建。
行@mkdir -p $(BUILDDIR)
需要变成@mkdir -p $(dir $@)
来解决这个问题。