安徽理工大学：《Linux开发基础 Development Foundation on Linux OS》课程教学资源（PPT课件讲稿）GNU C/C++ programming、CGI programming in GNU C/C++ language（方贤进）

②安薇理工大学 ANHUI UNIVERSITY OF SCIENCE TECHNOLOGY Linux开发基础 Development Foundation on Linux Os 方贤进,PhD& Associate Prof 安徽理工大学计算机科学与工程学院

安徽理工大学 计算机科学与工程学院 Linux开发基础 Development Foundation on Linux OS 方贤进, Ph.D & Associate Prof

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG Section 2 GNU C/C++ programming

3 Section 2 GNU C/C++ programming

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG hat is GNU? The GNU operating system is a complete free software system, upward-compatible with Unix. GNU stands for GNU's Not Unix" richard Stallman made the initial Announcement of the GNU Pro ject in September 1983 Source: http://www.gnu.org/gnu/initial announcement. htm

4 What is GNU? ➢ The GNU operating system is a complete free software system, upward-compatible with Unix. GNU stands for “GNU's Not Unix”. Richard Stallman made the Initial Announcement of the GNU Project in September 1983. Source: http://www.gnu.org/gnu/initial￾announcement.html

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG What is Free Software? Free software"is a matter of liberty, not price. To understand the concept, you should think of"free"as in"free speech", not as in free beer Free software is a matter of the users' freedom to run, copy distribute, study, change and improve the software. More precisely. it refers to four kinds of freedom for the users of the software a The freedom to run the program, for any purpose(freedom O) a The freedom to study how the program works, and adapt it to your needs(freedom 1). access to the source code is a precondition for this a The freedom to redistribute copies so you can help your neighbor (freedom 2) a The freedom to improve the program, and release your improvements to the public, so that the whole community benefits (freedom 3). Access to the source code is a precondition for this

5 What is Free Software? ➢ “Free software” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech”, not as in “free beer”. ➢ Free software is a matter of the users' freedom to run, copy, distribute, study, change and improve the software. More precisely, it refers to four kinds of freedom, for the users of the software:  The freedom to run the program, for any purpose (freedom 0).  The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the source code is a precondition for this.  The freedom to redistribute copies so you can help your neighbor (freedom 2).  The freedom to improve the program, and release your improvements to the public, so that the whole community benefits (freedom 3). Access to the source code is a precondition for this

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG hat is gcc? GCC, the GNU Compiler Collection The GNU Compiler Collection includes front ends for C, C+t, Objective-C, Fortran, Java and Ada, as well as libraries for these languages(libstdc++, libgcj, ). GCC was originally written as the compiler for the GNU operating system. The GNU system was developed to be 100% free software free in the sense that it respects the user's freedom Sourcehttp://gcc.gnu.org

6 What is gcc? ➢ GCC, the GNU Compiler Collection. ➢ The GNU Compiler Collection includes front ends for C, C++, Objective-C, Fortran, Java, and Ada, as well as libraries for these languages (libstdc++, libgcj,...). GCC was originally written as the compiler for the GNU operating system. The GNU system was developed to be 100% free software, free in the sense that it respects the user's freedom. Source: http://gcc.gnu.org

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG 21 GNU C/C++编译器的使用 gc通过扩展名来判断文件的类型,从而确定用何种方式处理该文件 后缀名 说明 C语言源代码文件 C/cxc+源代码文件 h 程序所包含的头文件 已经预处理过的C语言源代码文件 已经预处理过的C++源代码文件 m Objective-C语言源代码文件 ss 汇编语言源代码文件 经过预编译的汇编语言源代码文件 a/。so 编译后的库代码 编译后的目标文件

7 后缀名 说明 .c C语言源代码文件 .C/.cc/.cxx C++源代码文件 .h 程序所包含的头文件 .i 已经预处理过的C语言源代码文件 .ii 已经预处理过的C++源代码文件 .m Objective-C语言源代码文件 .s 汇编语言源代码文件 .S 经过预编译的汇编语言源代码文件 .a/.so 编译后的库代码 .o 编译后的目标文件 2.1 GNU C/C++编译器的使用 gcc通过扩展名来判断文件的类型，从而确定用何种方式处理该文件

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG 21 GNU C/C++编译器的使用 gcc编译器选项和参数 参数 含义 -o Place the output into C Compile and assemble, but do not 99 db Produce debugging information for use by GDB O the compiler tries to reduce code size and execution time without performing any optimizations that take a great deal of com-pilaTion Time Produce debugging information in the operating systems native format. GDB can work with this debugging information I Add the directory dir to the list of directories to be searched for header files. Directories named by-i are searched before the L Search the library named library when linking

8 2.1 GNU C/C++编译器的使用 gcc 编译器选项和参数 参数 含义 -o Place the output into -c Compile and assemble, but do not link -ggdb Produce debugging information for use by GDB. -O the compiler tries to reduce code size and execution time, without performing any optimizations that take a great deal of com-pilation time. -g Produce debugging information in the operating system's native format. GDB can work with this debugging information. -I Add the directory dir to the list of directories to be searched for header files. Directories named by -I are searched before the -L Search the library named library when linking

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG 21 GNU C/C++编译器的使用 1、直接通过编译生成目标代码可执行文件: Sgcc hello. c -o hello 2、如果一个程序包含有多个源文件,则也可直接生成目标代码: void f10 printf("%sIn","function 1); void f20 printf( %sIn", function 2); maino f10 f20 Sgcc f1.c f2.c main. c -o main

9 2.1 GNU C/C++编译器的使用 1、直接通过编译生成目标代码可执行文件： $gcc hello.c –o hello 2、如果一个程序包含有多个源文件，则也可直接生成目标代码： void f1() { printf(“%s\n”, "function 1"); } void f2() { printf("%s\n", "function 2"); } main() { f1(); f2(); } $gcc f1.c f2.c main.c –o main

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG > Linux上广泛使用的C语言编译器是GNUC编译器,GNU c建立在自由软件基金会的编程许可证的基础上,可以自 由发布。在 Linux下,一个完整的c语言开发环境到少包 括以下三个组成部分: √函数库gbc(在/us/ib和/ib目录中) √编译器gcc √系统头文件q! ibc header(h) glibc是构成一个完整的C语言开发环境所必不可少的组成 邗分,也是Lnux下C语言的主要函数库。 glibc_header中包含了系统编译源代码所需要的声明文 件如果缺少系统头文件,很多用到系统功能的c程序将无 法编译。(包含在/usr/ include/及其子目录中) 10

10 ➢ Linux上广泛使用的C语言编译器是GNU C编译器，GNU C建立在自由软件基金会的编程许可证的基础上，可以自 由发布。在Linux下，一个完整的C语言开发环境到少包 括以下三个组成部分： ✓函数库glibc (在/usr/lib和/lib目录中) ✓编译器gcc ✓系统头文件glibc_header (*.h) ➢ glibc是构成一个完整的C语言开发环境所必不可少的组成 部分，也是Linux下C语言的主要函数库。 ➢ glibc_header中包含了系统编译源代码所需要的声明文 件,如果缺少系统头文件，很多用到系统功能的C程序将无 法编译。(包含在/usr/include/及其子目录中)

⑧安薇理工大学 ANHUI UNIVERSITY OFSCIENCE TECHNOLOG 2.2GNUC/C++函数库 定义:是一些预先编译好的函数的集合,那些函数都是按照可再使用 的原则编写的。它们通常是一组相互关联的用来完成某项常见工作的 函数构成(比如c库里面的标准辅入输出函数、时间函数和数学函数 等)。 函数库中的函数可以通过连接程序与应用程序进行连接,而不必在每 次开发程序时都对这些通用的函数进行编译 不同类型的应用程序将会使用不同的函数库。如数学应用将使用数学 库 Elibm(usr/ib/ibma,/usr/ib/ibm.so),标准的C库 libc(usr/ib/ibc.a, /usr/lib/libc. so) 注意:*h只是对函数的声明( declaration),函数的定义是在具体的函 数库中

11 2.2 GNU C/C++函数库 ➢ 定义：是一些预先编译好的函数的集合，那些函数都是按照可再使用 的原则编写的。它们通常是一组相互关联的用来完成某项常见工作的 函数构成（比如c库里面的标准输入输出函数、时间函数和数学函数 等）。 ➢ 函数库中的函数可以通过连接程序与应用程序进行连接，而不必在每 次开发程序时都对这些通用的函数进行编译。 ➢ 不同类型的应用程序将会使用不同的函数库。如数学应用将使用数学 库libm(/usr/lib/libm.a, /usr/lib/libm.so)，标准的C库 libc(/usr/lib/libc.a,/usr/lib/libc.so)。 注意：*.h只是对函数的声明（declaration）,函数的定义是在具体的函 数库中