0. Raymond的前言

在<<学习GNU Emacs(第二版)>>的前言中,Eric Raymond写道:

我有很多知识都是通过阅读别人的程序代码而掌握的,这些"前辈"包括: Olin Shivers, Jamie Zawinski, Kyle Jones, Barry Warsaw, Roland McGrath, Richard Stallman本人(当然得有他)和许多其他程序员。

1. glib?

glib是什么?
GLIB - Library of useful routines for C programming

2. 下载源代码

$ pwd /home/c-aries/source/glib $ cat url http://ftp.gnome.org/pub/gnome/sources/glib/2.16/glib-2.16.6.tar.bz2 http://ftp.gnome.org/pub/gnome/sources/glib/2.16/glib-2.16.6.md5sum $ wget -c -i url

3. 编译源代码,解决依赖关系,安装

$ tar xvf glib-2.16.6.tar.bz2 $ cd glib-2.16.6

在 ./mybuild 文件夹下进行编译
程序安装的目标目录为 ./mybuild/work

编译和安装的命令如下:

$ mkdir mybuild $ cd mybuild $ ../configure --prefix=`pwd`/work $ make $ make install

4. 学习源代码

这里以glib源代码中宏定义G_GNUC_EXTENSION的学习笔记为例:
G_GNUC_EXTENSION定义于 glib/gmacros.h

4.1 G_GNUC_EXTENSION的实现

#if     __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 8) #  define G_GNUC_EXTENSION __extension__ #else #  define G_GNUC_EXTENSION #endif

4.2 为何出现G_GNUC_EXTENSION?

比如在C语言中使用long long数据类型时,如果使用__extension__修饰,此时gcc使用'-ansi -pedantic'选项则不会报错。
'-ansi -pedantic'选项的含义如下:

-ansi     Specify the standard to which the code should conform. Currently CPP knows     about C and C++ standards; others may be added in the future. -pedantic     Issue all the mandatory diagnostics listed in the C standard. Some of them     are left out by default, since they trigger frequently on harmless code.

4.3 G_GNUC_EXTENSION使用实例

G_GNUC_EXTENSION typedef unsigned long long guint64;

5 修改源代码,编程调试

为glib修改源代码,添加功能,找bug的趣事就留给大家慢慢玩了
这里介绍如何使用自己修改和编译得来的glib函数库进行编程调试

5.1 查看cflags编译选项

$ pkg-config --cflags mybuild/work/lib/pkgconfig/glib-2.0.pc -I/home/c-aries/source/glib/glib-2.16.6/mybuild/work/include/glib-2.0 -I/home/c-aries/source/glib/glib-2.16.6/mybuild/work/lib/glib-2.0/include

5.2 查看libs链接选项

$ pkg-config --libs mybuild/work/lib/pkgconfig/glib-2.0.pc -L/home/c-aries/source/glib/glib-2.16.6/mybuild/work/lib -lglib-2.0

 
5.3 编程实例

使用自己修改和编译得来的glib函数库进行编程调试
在笔者的cvs本地仓库checkout出test-glib项目，程序运行后，打印出64位无符号整数的最大值

$ pwd /home/c-aries/develop $ cvs co test-glib $ cd test-glib/ $ make $ ./main The Largest Number Of 64 Bits: 18446744073709551615

test-glib项目的源代码如下:

$ cvs co -p test-glib cvs checkout: Updating test-glib =================================================================== Checking out test-glib/Makefile RCS:  /home/c-aries/cvs/test-glib/Makefile,v VERS: 1.1.1.1 *************** CC = gcc CFLAGS = -Wall -Werror -Wcast-align -g LDFLAGS = MAINOBJECT = main.o opt.o TESTOBJECT = test.o GLIBHOME = /home/c-aries/source/glib/glib-2.16.6/mybuild/work GLIBPC = $(GLIBHOME)/lib/pkgconfig/glib-2.0.pc GLIBCFLAGS = `pkg-config --cflags $(GLIBPC)` GLIBLIBS = `pkg-config --libs $(GLIBPC)` all: main main: $(MAINOBJECT)     $(CC) $(LDFLAGS) $(GLIBLIBS) $(MAINOBJECT) -o $@ test: $(TESTOBJECT)     $(CC) $(LDFLAGS) $(TESTOBJECT) -o $@ main.o: main.c     $(CC) $(CFLAGS) $(GLIBCFLAGS) -c $< opt.o: opt.c     $(CC) $(CFLAGS) -c $< test.o: test.c     $(CC) $(CFLAGS) -c $< clean:     rm -f *.o *~ *.log a.out main test .PHONY: all clean =================================================================== Checking out test-glib/main.c RCS:  /home/c-aries/cvs/test-glib/main.c,v VERS: 1.2 *************** #include <stdio.h> #include <stdlib.h> #include <glib.h> #include "opt.h" int main(int argc, char *argv[]) {   options_init();   options_deal(argc, argv);   g_print("The Largest Number Of 64 Bits: %" G_GUINT64_FORMAT "\n",\       G_MAXUINT64);   exit(EXIT_SUCCESS); } =================================================================== Checking out test-glib/opt.c RCS:  /home/c-aries/cvs/test-glib/opt.c,v VERS: 1.1.1.1 *************** #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include "opt.h" struct options opt; static void show_usage(); static void show_usage() {   printf("usage: main [options]\n\ -h 打印该帮助信息\n\ -v 显示程序内部提示\n"); } void options_init() {   opt.verbose = 0; } void options_deal(int argc, char *argv[]) {   int my_opt;   while ((my_opt = getopt(argc, argv, "hv")) != -1) {     switch(my_opt) {     case 'h':       show_usage();       exit(EXIT_SUCCESS);     case 'v':       opt.verbose = 1;       break;     default:       show_usage();       exit(EXIT_FAILURE);     }   } } =================================================================== Checking out test-glib/opt.h RCS:  /home/c-aries/cvs/test-glib/opt.h,v VERS: 1.1.1.1 *************** #ifndef OPT_H #define OPT_H struct options {   int verbose; }; void options_init(); void options_deal(int argc, char *argv[]); #endif $

glib