Basic usage of GCC

Catalog

One 、GCC

Two 、GCC、gcc、g++ The relationship between the three

3、 ... and 、gcc The build process

Four 、 file type

5、 ... and 、gcc Compilation options

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One 、GCC

GCC(GNU Compiler Collection) namely GNU Compiler Suite , It belongs to a programming language compiler , Its original name was GCC（GNU C Compiler） namely GNU c Language compiler , Although the abbreviations are the same, the functions are very different .GCC The original intention is to GNU A compiler specially written by the operating system , The original GNU Is dedicated to compiling C Code , Now it has been extended to compile C、C++、Java、Objective-C A collection of compilers for many programming languages

Two 、GCC、gcc、g++ The relationship between the three

  gcc（GNU C Compiler） yes GCC Medium c compiler , and g++（GNU C++ Compiler） yes GCC Medium c++ compiler .gcc and g++ Both can be compiled c and cpp file , But there are differences .gcc Compiling cpp The grammar is in accordance with c To compile, but cannot be linked to by default c++ The library of （gcc Default link c library ,g++ Default link c++ library ）.g++ compile .c and .cpp All the documents are unified according to cpp Syntax rules to compile . So generally compile c use gcc, compile c++ use g++.

3、 ... and 、gcc The build process

use gcc compile *.c Files do not directly generate executable files , In the process, it also goes through pretreatment 、 Compile and assemble several processes

 

• In the pretreatment stage ,gcc The header file to be called will be included , Replace macro constants and macro code snippets
• In the compilation phase ,gcc Will check the normalization of the code 、 Whether there are grammar mistakes, etc , After checking to be correct ,gcc Will translate the document into .s Suffix assembly file
• In the assembly phase ,gcc Will be able to .s Suffix assembly file Translate into .o Suffix target file ( Binary files recognized by the machine )
• In the link phase ,gcc Will link the target file to the Library , Generate executable files

Four 、 file type

stay Linux In the system , There is no uniform suffix for executable files , The system distinguishes executable files from non executable files according to the attributes of files . and gcc The suffix is used to distinguish the category of the input file , Let's introduce gcc Some of the agreed rules followed

.c A file with a suffix ,C Language source code file ;

.a A file with a suffix , Is a library file composed of object files ;

.C,.cc or .cxx A file with a suffix , yes C++ Source code file ;

.h A file with a suffix , Is the header file included in the program ;

.i A file with a suffix , It's pretreated C Source code file ;

.m A file with a suffix , yes Objective-C Source code file ;

.o A file with a suffix , Is the compiled target file ;

.s A file with a suffix , Is the assembly language source code file ;

.S A file with a suffix , Is a precompiled assembly language source code file

5、 ... and 、gcc Compilation options

Options	effect
E	Activate preprocessing ; The header file 、 Macro expansion （.i file ）
S	Activate preprocessing 、 compile ; Generate assembly code （.s file ）
c	Activate preprocessing 、 compile 、 assembly ; Generate target file （.o file ）
nothing	Activate preprocessing 、 compile 、 assembly 、 link ; Generate executable files （.out file ）
o	Generate goals
Wall	Open compilation alarm （ all ）
g	Embed debugging information , convenient gdb debugging
llib	link lib library （ Here is lowercase L ） amount to C++ #pragma comment(lib, “xxx.lib”)
Idir	increase include Catalog ( This is capital i ) Header file path
LDir	increase lib Catalog （ Compiling static and dynamic libraries ）

Suppose the source file name is test.c.

1. No option to compile Links

usage ：gcc test.c

effect ： take test.c Preprocessing 、 assembly 、 Compile and link to form an executable . The output file is not specified here , The default output is a.out.

2. Options -o

usage ：gcc test.c -o test

effect ： take test.c Preprocessing 、 assembly 、 Compile and link to form an executable test.-o Option is used to specify the file name of the output file .

3. Options -E

usage ：gcc -E test.c -o test.i

effect ： take test.c Preprocessing output test.i file .

4. Options -S

usage ：gcc -S test.i 

effect ： Will preprocess the output file test.i Assemble into test.s file .

5. Options -c

usage ：gcc -c test.s

effect ： Will assemble the output file test.s Compile output test.o file .

6. No option link

usage ：gcc test.o -o test

effect ： The output file will be compiled test.o Link to final executable test.

7. Options -O

usage ：gcc -O1 test.c -o test

effect ： Use compile optimization level 1 compiler . The level of 1~3, The higher the level, the better the optimization effect , But the longer it takes to compile .