从 Makefile 中的 $@ 获取文件名

Question

this makefile works great when all the cpp files are in one directory. upon creating subdirectories it fails to create the *.o files because its missing subdirectories:

Directory Structure

.
├── 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 $@ $<

an example output of this code is:

 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

how can the command be changed so that it is just the name of the o file and not the full path. using the special variable $@.

(basename $@) returned build/Board/Board but need it to be board.o

=============== Solution ===============

The Makefile was failing because the subdirectories were not created. the line @mkdir -p $(BUILDDIR) needed to become @mkdir -p $(dir $@) to remedy this.

Answer 1

I don't really understand what you mean by how can the command be changed so that it is just the name of the o file ... which command?

It's not correct for a recipe to create a file which is not exactly the value of $@ . That's what make expects you to create and things won't work correctly if your recipe creates some other file.

In any event the functions GNU make supports are available here . The one you want is $(notdir $@) . However you don't even need that, because there are variants of the automatic variables for the directory ( $(@D) ) and file ( $(@F) ).