当前位置：网站首页>[C and pointer Chapter 14] preprocessor
[C and pointer Chapter 14] preprocessor
2022-07-24 11:49:00 【Xiaoyuan Xiaoyuan eats dumplings】
The first 14 Chapter The preprocessor
14.1 Predefined symbols
#include<stdio.h>
int main()
{
printf(" The name of the source file to compile ：%s \n",__FILE__);
printf(" The line number of the current line of the file ：%d \n",__LINE__);
printf(" The date the file was compiled ：%s\n",__DATE__);
printf(" When the file was compiled ：%s\n",__TIME__);
printf(" Whether the compiler is ANSI C：%d\n",__STDC__);
return 0;
}
==========================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
The name of the source file to compile ：test.c
The line number of the current line of the file ：7
The date the file was compiled ：Jul 21 2022
When the file was compiled ：15:04:21
Whether the compiler is ANSI C：1
14.2 #define
#include<stdio.h>
#define DEBUG_PRINT printf("File %s line %d:"\ "x=%d,y=%d,z=%d",\ __FILE__,__LINE__,\ x,y,z)
int main()
{
int x=1,y=1,z=1;
x *= 2;
y += x;
z = x*y;
DEBUG_PRINT;
return 0;
}
=====================================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
File test.c line 13:x=2,y=3,z=6
#include<stdio.h>
#define PROCESS_LOOP for(int i=0;i<10;i++) \ {
\ printf("value=%d\n",i); \ }
int main()
{
PROCESS_LOOP;
return 0;
}
===================================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
value=0
value=1
value=2
value=3
value=4
value=5
value=6
value=7
value=8
value=9
14.2.1 macro
#include<stdio.h>
#define SQUARE(x) x*x
int main()
{
printf("result = %d",SQUARE(6));
return 0;
}
=========================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
result = 36
#include<stdio.h>
#define SQUARE(x) x*x
int main()
{
int a=5;
printf("result = %d",SQUARE(a+1));
return 0;
}
=========================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
result = 11
#include<stdio.h>
#define SQUARE(x) (x)*(x)
int main()
{
int a=5;
printf("result = %d",SQUARE(a+1));
return 0;
}
=======================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
result = 36
#include<stdio.h>
#define DOUBLE(x) (x)+(x)
int main()
{
int a=5;
printf("result = %d",10*DOUBLE(a));
return 0;
}
=====================================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
result = 55
#include<stdio.h>
#define DOUBLE(x) ((x)+(x))
int main()
{
int a=5;
printf("result = %d",10*DOUBLE(a));
return 0;
}
===========================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
result = 100
14.2.2 #define Replace
#include<stdio.h>
#define PRINT(FORMAT,VALUE) \ printf("The value is " FORMAT "\n",VALUE)
int main()
{
PRINT("%d",24);
return 0;
}
===============================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
The value is 24
#include<stdio.h>
#define PRINT(FORMAT,VALUE) \ printf("The value of " #VALUE \ " is " FORMAT "\n",VALUE)
int main()
{
int x = 20;
PRINT("%d",x+3);
return 0;
}
========================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
The value of x+3 is 23
#include<stdio.h>
#define ADD_TO_SUM(sum_number,value) \ sum ## sum_number += value
int main()
{
int sum1 = 20;
ADD_TO_SUM(1,10);
printf("sum1 The value of is ：%d",sum1);
return 0;
}
============================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
sum1 The value of is ：30
14.2.3 Macros and functions
#include<stdio.h>
#define MAX(a,b) ((a)>(b)?(a):(b))
int main()
{
int a = 10,b = 15;
printf("MAX = %d",MAX(a,b));
return 0;
}
===================================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
MAX = 15
#include<stdio.h>
#include<stdlib.h>
#define MALLOC(n,type) \ ((type *)malloc((n) * sizeof(type)))
int main()
{
int *p = MALLOC(25,int);
if(p!=NULL)
printf("OK");
return 0;
}
===========================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
OK
14.2.4 Macro parameters with side effects
#include<stdio.h>
#define MAX(a,b) ((a)>(b)?(a):(b))
int main()
{
int x=5,y=8;
int z = MAX(x++,y++);
printf("x = %d,y = %d,z = %d",x,y,z);
return 0;
}
===============================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
x = 6,y = 10,z = 9
14.2.5 Naming conventions
14.2.6 #undef
14.2.7 Command line definition
14.3 Conditional compilation
#include<stdio.h>
#define DEBUG 1
int main()
{
#if DEBUG
printf("DEBUG is 1 \n");
#endif
return 0;
}
===========================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
DEBUG is 1
#include<stdio.h>
#define DEBUG1 0
#define DEBUG2 0
#define DEBUG3 1
int main()
{
#if DEBUG1
printf("DEBUG1 \n");
#elif DEBUG2
printf("DEBUG2 \n");
#elif DEBUG3
printf("DEBUG3 \n");
#endif
return 0;
}
=================================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
DEBUG3
14.3.1 Is it defined
#include<stdio.h>
// #define symbol 0
#define X 0
#define ABC 0
#define BCD 0
int main()
{
// #if defined(symbol)
// printf("symbol has been defined");
// #endif
// #ifdef symbol
// printf("symbol has been defined");
// #endif
// #if !defined(symbol)
// printf("symbol has not been defined");
// #endif
// #ifndef symbol
// printf("symbol has been defined");
// #endif
#if X>0||(defined(ABC) &&defined(BCD))
printf("X>0||(defined(ABC) &&defined(BCD))");
#endif
return 0;
}
14.3.2 Nested instruction
#include<stdio.h>
#define OS_UNIX 0
#define OPTION2 0
int main()
{
#if defined(OS_UNIX)
#ifdef OPTION1
printf("OPTION1");
#endif
#ifdef OPTION2
printf("OPTION2");
#endif
#elif defined(OS_MSDOS)
#ifdef OPTION2
printf("OPTION2");
#endif
#endif
return 0;
}
=============================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc tempCodeRunnerFile.c -o tempCodeRunnerFile } ; if ($?) {
.\tempCodeRunnerFile }
OPTION2
14.4 File contains
14.4.1 The function library file contains
14.4.2 The local file contains
14.4.3 Nested files contain
//test.h
#ifndef _test_H
#define _test_H 1
#endif
========================================================
//test.c
#include<stdio.h>
#include "test.h"
int main()
{
printf("%d",_test_H);
return 0;
}
============================================
PS E:\project_C> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
1
14.5 Other instructions
#include<stdio.h>
// #define OPTION_A 1
int main()
{
#if defined(OPTION_A)
printf("123");
#else
#error no defined
#endif
return 0;
}
==============================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
test.c: In function 'main':
test.c:9:10: error: #error no defined
#error no defined
#include<stdio.h>
#line 10 "string"
// The first 10 That's ok
int main() // The first 11 That's ok
{
// The first 12 That's ok
printf("%d %s",__LINE__,__FILE__); // The first 13 That's ok
return 0;
}
===========================================
PS E:\project_C\test> cd "e:\project_C\test\" ; if ($?) {
gcc test.c -o test } ; if ($?) {
.\test }
13 string
14.6 summary
14.7 Summary of warnings
14.8 Summary of programming tips
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