C语言可变参数与函数参数的内存对齐详解

void va_start(va_list ap, last_arg)


type va_arg(va_list ap, type)


void va_end(va_list ap)

#include <stdio.h>
#include <stdarg.h>//引用可变参数宏头文件

int getSum(int num, ...)//定义可变参数的函数
{
    int sum = 0;
    va_list list;//创建va_list类型的变量
    va_start(list, num);//初始化可变参数list
    for(int i = 0; i < num; i++)
    {
        sum += va_arg(list, int);//访问参数列表中的每个项
    }
    va_end(list);//释放内存
    return sum;
}

int main()
{
    printf("%d\n", getSum(4, 4, 5, 6, 7));
}

#include <stdio.h>
#include <stdarg.h>//引用可变参数宏头文件

void func(char *demo, ...)
{
    char *pstr = NULL;
    va_list list;
    va_start(list, demo);
    while(1)
    {
        pstr = va_arg(list, char *);
        if(*pstr == '$')//以 '$' 代表结束
            break;
        printf("%s\n", pstr);
    }
    va_end(list);
}

int main()
{
    func("demo", "ABC", "123", "Hello Wolrd!", '$');
}

#include <stdio.h>

int getSum(int num, ...)
{
    int sum = 0;
    char *p = NULL;
    p = (char*)&num;
    p += 8;
    for(int i = 0; i < num; i++)
    {
        sum += *((int*)p);
        p += 8;
    }
    return sum;
}
int main()
{
    int a = 1;
    int b = 2;
    int c = 3;
    printf("sum = %d\n", getSum(3, a, b, c));
}

#include <stdio.h>

void func(int a, int b, int c)
{
    printf("a = %p\n", &a);
    printf("b = %p\n", &b);
    printf("c = %p\n", &c);
}
int main()
{
	int a,b,c;
	func(a, b, c);
}

#include <stdio.h>

void func(char a, short b, long long c)
{
    printf("a = %p\n", &a);
    printf("b = %p\n", &b);
    printf("c = %p\n", &c);
}

int main()
{
    char a = 1;
    short b = 2;
    long long c = 3;
    func(a, b, c);
}

#include <stdio.h>

void func(double a, double b, double c)
{
    printf("a = %p\n", &a);
    printf("b = %p\n", &b);
    printf("c = %p\n", &c);
}

int main()
{
    double a = 1;
    double b = 2;
    double c = 3;
    func(a, b, c);
}

#include <stdio.h>
typedef struct
{
    char c[7];
}str_t;

void func(str_t a, str_t b, str_t c)
{
    printf("a = %p\n", &a);
    printf("b = %p\n", &b);
    printf("c = %p\n", &c);
}

int main()
{
    str_t a;
    str_t b;
    str_t c;
    func(a, b, c);
}

#include <stdio.h>
typedef struct
{
    char c[4];
}str_t;

void func(str_t a, str_t b, str_t c)
{
    printf("a = %p\n", &a);
    printf("b = %p\n", &b);
    printf("c = %p\n", &c);
}

int main()
{
    str_t a;
    str_t b;
    str_t c;
    func(a, b, c);
}