/*------------------------------------------------------------------------------
HELLO.C
Copyright 1995-1999 Keil Software, Inc.
------------------------------------------------------------------------------*/
#include <REG52.H> /* special function register declarations */
/* for the intended 8051 derivative */
#include <stdio.h> /* prototype declarations for I/O functions */
#include <stdlib.h>
#include <string.h>
#include <ABSACC.H>
#define ERR_CASE 1 //test pointer
#ifdef MONITOR51 /* Debugging with Monitor-51 needs */
char code reserve [3] _at_ 0x23; /* space for serial interrupt if */
#endif /* Stop Exection with Serial Intr. */
/* is enabled */
#if ERR_CASE
void test_func(char *str)
{
char *p;
printf("%s/n",str);
p=malloc(100);
memset (p, '/0', sizeof (p));
strncpy(p,"test string",100);
str=p;
}
#else
void test_func(char **str)
{
#if 0
char *p;
p=malloc(100);
memset (p, '/0', sizeof (p));
strncpy(p,"test string",100);
*str=p;
#else
*str=malloc(100);
memset (*str, '/0', sizeof (*str));
strncpy(*str,"test string",100);
#endif
}
#endif
/*---------------------------------------------
The main C function. Program execution starts
here after stack initialization.
------------------------------------------------*/
void main (void) {
char *p_str="init string";
/*------------------------------------------------
Setup the serial port for 1200 baud at 16MHz.
------------------------------------------------*/
#ifndef MONITOR51
SCON = 0x50; /* SCON: mode 1, 8-bit UART, enable rcvr */
TMOD |= 0x20; /* TMOD: timer 1, mode 2, 8-bit reload */
TH1 = 221; /* TH1: reload value for 1200 baud @ 16MHz */
TR1 = 1; /* TR1: timer 1 run */
TI = 1; /* TI: set TI to send first char of UART */
#endif
/*------------------------------------------------
Note that an embedded program never exits (because
there is no operating system to return to). It
must loop and execute forever.
------------------------------------------------*/
init_mempool (&XBYTE [0x2000], 0x1000);
/* initialize memory pool at xdata 0x2000
for 4096 bytes */
#if ERR_CASE
test_func(p_str);//把指向的内容传进去,只能读取传进的内容,不能改写;并不影响指针,退出时指针并不变化.
#else
test_func(&p_str);//把指针传进去,对指针进行操作
#endif
if(NULL!=p_str)
printf ("%s/n",p_str); /* Print "Hello World" */
while (1) {
P1 ^= 0x01; /* Toggle P1.0 each time we print */
}
}