自写printf函数遇到的问题，可变参

#include<stdio.h>
#include<stdarg.h>

void myPrintf(const char *formatStr,...);

void myPrintf(const char *formatStr,...)
{
        va_list begin;
        char ch;
        int i;
        int dh;
        va_start(begin,formatStr);
        for(i = 0;formatStr[i];i++)
        {
                if(formatStr[i] == '%')
                {
                        i++;
                        switch (formatStr[i])
                        {
                                        case 'c':
//提示下面这一行有错误
//myPrintf.c:21:11: warning: ‘char’ is promoted to ‘int’ when passed through ‘...’ //[enabled by default]
//myPrintf.c:21:11: note: (so you should pass ‘int’ not ‘char’ to ‘va_arg’)
//myPrintf.c:21:11: note: if this code is reached, the program will abort

/*******有错误的一行*/                  ch = va_arg(begin,char);
                                        putchar(ch);
                                        break;
                        }
                }
                else
                putchar(formatStr[i]);
        }

}

int main(void)
{
        char first = 'g';
        myPrintf("abcdef%c",first);
        return 0;
}

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