• <ins id="pjuwb"></ins>
    <blockquote id="pjuwb"><pre id="pjuwb"></pre></blockquote>
    <noscript id="pjuwb"></noscript>
          <sup id="pjuwb"><pre id="pjuwb"></pre></sup>
            <dd id="pjuwb"></dd>
            <abbr id="pjuwb"></abbr>
            <2025年7月>
            293012345
            6789101112
            13141516171819
            20212223242526
            272829303112
            3456789

            統計

            • 隨筆 - 24
            • 文章 - 0
            • 評論 - 17
            • 引用 - 0

            常用鏈接

            留言簿(4)

            隨筆分類

            隨筆檔案

            相冊

            搜索

            •  

            最新評論

            閱讀排行榜

            評論排行榜

            有關include guard的一個好帖子(收藏)
            終于弄清楚了原來說的同一個頭文件不能被兩次或兩次以上包含是針對同一個源文件而言的。借用80后的流行語,真是漢哪!

            原貼地址:http://www.keil.com/forum/docs/thread10237.asp

            作者 Per Westermark

            The

            #ifndef xx
            #define xx
            ...
            #endif
            

            method is to make sure that a header file isn't included more than once from the same c file.

            You can not - and normally don't want to - stop multiple c files from including the same header file.

            A header file is included because:
            1) You have specifically added a line #include "xx" or #include <xx> in the source file. Don't do that unless you want the file to be included :)
            2) You are including one header file, that it it's turn (one or more steps away) includes another header file. But a header file should only contain a recursive #include if it really needs that other file for some declarations. Hence, you need to include it.

            What does this mean?

            If the header file must be seen by multiple source files, you can't use it to allocate global variables, since the linker would then complain about multiple sets of global variables with the same name. This can be solved with the following:

            //globals.h
            #ifndef _GLOBALS_H
            #define _GLOBALS_H
            #if defined MAIN
            #define EXTERN
            #else
            #define EXTERN extern
            #endif
            ...
            EXTERN int my_global_variable;
            #endif // _GLOBALS_H
            

            // main.c
            #define MAIN
            #include "globals.h"
            ...
            // misc.c
            #include "globals.h"
            ...
            

            In this case, only the inclusion in main.c will result in an "allocation" of global variables, because the #define EXTERN will be empty. All other source files that includes "globals.h" will just see the type information for the global variables.

            posted on 2009-02-19 09:04 小蔥蘸醬 閱讀(996) 評論(2)  編輯 收藏 引用

            評論

            # re: 有關include guard的一個好帖子(收藏) 2009-02-19 21:19 陳梓瀚(vczh)

            EXTERN的時候,如果剛好main沒有引用它,那就鏈接錯誤了- -#
              回復  更多評論    

            # re: 有關include guard的一個好帖子(收藏)[未登錄] 2009-02-20 16:15 小蔥蘸醬

            @陳梓瀚(vczh)
            歡迎評論!
            只要在include "globals.h"前定義了MAIN,就不會聯接錯誤,跟引用有什么關系呢?
              回復  更多評論    
            亚洲国产成人久久综合一 | 国产福利电影一区二区三区久久老子无码午夜伦不 | 2020最新久久久视精品爱| 国内精品人妻无码久久久影院| 狠狠色婷婷久久一区二区| 奇米影视7777久久精品| 丰满少妇人妻久久久久久 | 中文精品久久久久国产网址| 九九久久精品无码专区| 中文字幕无码免费久久| 亚洲国产精品无码久久一区二区 | 久久国产精品成人免费| 久久久久亚洲精品日久生情 | 人妻无码久久一区二区三区免费| 国色天香久久久久久久小说| 麻豆精品久久精品色综合| 久久水蜜桃亚洲av无码精品麻豆| 成人免费网站久久久| 激情伊人五月天久久综合| 九九久久精品国产| 久久精品亚洲精品国产色婷| 亚洲午夜久久久久久久久电影网| 天天综合久久久网| 中文字幕精品久久久久人妻| 日韩欧美亚洲综合久久影院Ds| 天天爽天天爽天天片a久久网| 无码八A片人妻少妇久久| 久久免费观看视频| 亚洲а∨天堂久久精品| 久久青青草原亚洲av无码app| 国产亚洲成人久久| 99久久无码一区人妻a黑| 7777久久久国产精品消防器材| 久久97久久97精品免视看秋霞| 99久久人妻无码精品系列| 久久人做人爽一区二区三区| 久久狠狠一本精品综合网| 久久99国产精品久久99小说| 久久99精品国产99久久6| 国产精品毛片久久久久久久| 国产精品久久久久影院嫩草|