C++ Makefile：如何正确包含头文件及其目录？

Makefile: How to correctly include header file and its directory?

提问by tonga

I have the following makefile:

我有以下生成文件：

CC=g++
INC_DIR = ../StdCUtil
CFLAGS=-c -Wall -I$(INC_DIR)
DEPS = split.h

all: Lock.o DBC.o Trace.o

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

clean:
    rm -rf *o all

This makefile and all three source files Lock.cpp, DBC.cpp, Trace.cppare located in the current directory called Core. One of the source file Trace.cppcontains a line that includes a header file outside the current directory:

此生成的文件和所有三个源文件Lock.cpp，DBC.cpp，Trace.cpp位于被称为当前目录Core。其中一个源文件Trace.cpp包含一行，该行包含当前目录之外的头文件：

//in Trace.cpp
#include "StdCUtil/split.h"

The header file split.his located at one level above the current directory and then in the subdirectory called StdCUtil. So that's why I added INC_DIR = ../StdCUtilin the makefile. The overall directory structure looks like the following:

头文件split.h位于当前目录的上一级，然后位于名为StdCUtil. 所以这就是我INC_DIR = ../StdCUtil在makefile中添加的原因。整体目录结构如下所示：

root
  |___Core
  |     |
  |     |____Makefile
  |     |____DBC.cpp
  |     |____Lock.cpp
  |     |____Trace.cpp
  |
  |___StdCUtil
        |___split.h

But when I make it, it gives me the error:

但是当我成功时，它给了我错误：

Trace.cpp:8:28: fatal error: StdCUtil/split.h: No such file or directory
 #include "StdCUtil/split.h"
                            ^
compilation terminated.
<builtin>: recipe for target 'Trace.o' failed

Why this doesn't find the header file split.heven if I specify the INC_DIRin the makefile? How to correct this?

为什么split.h即使我INC_DIR在 makefile 中指定了头文件也找不到头文件？如何纠正这个？

回答by David Hammen

These lines in your makefile,

你的makefile中的这些行，

INC_DIR = ../StdCUtil
CFLAGS=-c -Wall -I$(INC_DIR)
DEPS = split.h

and this line in your .cpp file,

和你的 .cpp 文件中的这一行，

#include "StdCUtil/split.h"

are in conflict.

处于冲突中。

With your makefile in your source directory and with that -Ioption you should be using #include "split.h"in your source file, and your dependency should be ../StdCUtil/split.h.

使用源目录中的 makefile 并使用该-I选项，您应该#include "split.h"在源文件中使用，并且您的依赖项应该是../StdCUtil/split.h.

Another option:

另外一个选项：

INC_DIR = ../StdCUtil
CFLAGS=-c -Wall -I$(INC_DIR)/..  # Ugly!
DEPS = $(INC_DIR)/split.h

With this your #includedirective would remain as #include "StdCUtil/split.h".

有了这个，您的#include指令将保持为#include "StdCUtil/split.h".

Yet another option is to place your makefile in the parent directory:

另一种选择是将您的 makefile 放在父目录中：

root
  |____Makefile
  |
  |___Core
  |     |____DBC.cpp
  |     |____Lock.cpp
  |     |____Trace.cpp
  |
  |___StdCUtil
        |___split.h

With this layout it is common to put the object files (and possibly the executable) in a subdirectory that is parallel to your Coreand StdCUtildirectories. Object, for example. With this, your makefile becomes:

使用这种布局，通常将目标文件（可能还有可执行文件）放在与您的Core和StdCUtil目录平行的子目录中。Object， 例如。有了这个，你的makefile就变成了：

INC_DIR = StdCUtil
SRC_DIR = Core
OBJ_DIR = Object
CFLAGS  = -c -Wall -I.
SRCS = $(SRC_DIR)/Lock.cpp $(SRC_DIR)/DBC.cpp $(SRC_DIR)/Trace.cpp
OBJS = $(OBJ_DIR)/Lock.o $(OBJ_DIR)/DBC.o $(OBJ_DIR)/Trace.o
# Note: The above will soon get unwieldy.
# The wildcard and patsubt commands will come to your rescue.

DEPS = $(INC_DIR)/split.h
# Note: The above will soon get unwieldy.
# You will soon want to use an automatic dependency generator.


all: $(OBJS)

$(OBJ_DIR)/%.o: $(SRC_DIR)/%.cpp
  $(CC) $(CFLAGS) -c $< -o $@

$(OBJ_DIR)/Trace.o: $(DEPS)

回答by manlio

The preprocessor is looking for StdCUtil/split.hin

预处理器正在寻找StdCUtil/split.h中

• ./(i.e. /root/Core/, the directory that contains the #include statement). So ./+ StdCUtil/split.h= ./StdCUtil/split.hand the file is missing

• ./（即/root/Core/，包含#include 语句的目录）。所以./+ StdCUtil/split.h=./StdCUtil/split.h并且文件丢失

and in

并在

• $INC_DIR(i.e. ../StdCUtil/= /root/Core/../StdCUtil/= /root/StdCUtil/). So ../StdCUtil/+ StdCUtil/split.h= ../StdCUtil/StdCUtil/split.hand the file is missing

• $INC_DIR（即../StdCUtil/= /root/Core/../StdCUtil/= /root/StdCUtil/）。所以../StdCUtil/+ StdCUtil/split.h=../StdCUtil/StdCUtil/split.h并且文件丢失

You can fix the error changing the $INC_DIRvariable (best solution):

您可以修复更改$INC_DIR变量的错误（最佳解决方案）：

$INC_DIR = ../

or the include directive:

或包含指令：

#include "split.h"

but in this way you lost the "path syntax" that makes it very clear what namespace or module the header file belongs to.

但是通过这种方式，您丢失了“路径语法”，这使得头文件所属的命名空间或模块非常清楚。

Reference:

参考：

• C++ #include semantics

• C++ #include 语义

EDIT/UPDATE

编辑/更新

It should also be

也应该是

CXX = g++
CXXFLAGS = -c -Wall -I$(INC_DIR)

...

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

回答by Bill Perkins

Try INC_DIR=../ ../StdCUtil.

试试INC_DIR=../ ../StdCUtil。

Then, set CCFLAGS=-c -Wall $(addprefix -I,$(INC_DIR))

然后，设置 CCFLAGS=-c -Wall $(addprefix -I,$(INC_DIR))

EDIT: Also, modify your #includeto be #include <StdCUtil/split.h>so that the compiler knows to use -I rather than local path of the .cpp using the #include.

编辑：另外，修改你的#include，#include <StdCUtil/split.h>以便编译器知道使用 -I 而不是使用 .cpp 的本地路径#include。

回答by cmaster - reinstate monica

This is not a question about make, it is a question about the semantic of the #includedirective.

这不是关于 make 的问题，而是关于#include指令语义的问题。

The problem is, that there is no file at the path "../StdCUtil/StdCUtil/split.h". This is the path that results when the compiler combines the include path "../StdCUtil" with the relative path from the #includedirective "StdCUtil/split.h".

问题是，路径“../StdCUtil/StdCUtil/split.h”中没有文件。这是编译器将包含路径“../StdCUtil”与来自#include指令“StdCUtil/split.h”的相对路径组合在一起时产生的路径。

To fix this, just use -I..instead of -I../StdCUtil.

要解决此问题，只需使用-I..代替-I../StdCUtil。