头部更改不会触发重新生成.o (使用.d依赖文件)

Question

我有一个如此简单的makefile：

#Compiler flags
CC := gcc
INCLDIR := -I./includes

#Directories and files
BUILDDIR := build
STLIB := $(BUILDDIR)/libbinary_tree.a

DEPS:=$(BUILDDIR)/binary_tree.d

-include $(DEPS)

$(BUILDDIR)/binary_tree.o: ./source_files/binary_tree.c
    mkdir -p $(@D)
    $(CC) -c $< $(INCLDIR) -o $@
    $(CC) -MM $(INCLDIR) ./source_files/binary_tree.c > $(BUILDDIR)/binary_tree.d

.PHONY: build clean

build: $(BUILDDIR)/binary_tree.o
    ar -rcs $(STLIB) $(BUILDDIR)/binary_tree.o

clean:
    rm -r $(BUILDDIR)

首先调用make build创建包含binary_tree.o: source_files/binary_tree.c includes/binary_tree.h的./build/binary_tree.d文件，但是如果我更改标题includes/binary_tree.h，然后调用make build -它不重建build/binary_tree.o，只创建库/libbinary_tree.a。我不知道为什么makefile会忽略头文件中的更改。你能告诉我我的逻辑哪里错了吗？

Answer 1

因为，binary_tree.o与build/binary_tree.o不是同一个文件。

所以你对前提关系的定义是：

binary_tree.o: source_files/binary_tree.c includes/binary_tree.h

指的是与编译规则的目标完全不同的文件：

$(BUILDDIR)/binary_tree.o: ./source_files/binary_tree.c