论malloc()后忘记初始化(memset)的后果

始终牢记：malloc后，一定记得memset，否则，隐藏的BUG折腾死人！

下面这段简单的程序，在create_node()函数中，malloc后，忘了memset，结果运行时出现如下错误．还好代码规模不大，gdb跟踪后发现了异常．如果在一个庞大的工程中，忘了memset，问题就不一定好找了

$ ./NodeMallocFree 
key=the first element, value=Ala
key=t, value=same key but different value
段错误 (核心已转储)

NodeMallocFree.c:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define RET_TRUE     0
#define RET_FALSE   -1

struct node {
	char *key;
	char *value;
	struct node *next;
};

static void free_node(struct node **p)
{
	struct node *n = *p;
	if(NULL == n)
		return;

	if(n->key)
		free(n->key);

	if(n->value)
		free(n->value);

	n->key = NULL;
	n->value = NULL;

	free(n);
	n = NULL;
}

static int copy_node_content(char **dst, char *src)
{
	int len;

	if(*dst || NULL == src)
		return RET_FALSE;

	len = strlen(src);
	*dst = malloc(len+1);
	memset(*dst, 0, len+1);
	strncpy(*dst, src, len);	

	return RET_TRUE;
}

static struct node * create_node(char *key, char *value)
{
	struct node *n;

	n = malloc(sizeof(struct node));
	// Be careful !!!!!
	//memset(n, 0, sizeof(struct node));
	if(key)
		copy_node_content(&n->key, key);
	if(value)
		copy_node_content(&n->value, value);

	return n;	
}

static void print_node(struct node *n)
{
	printf("key=%s, value=%s\n", n->key, n->value);
}


int main()
{
	struct node *n, *n2;

	n = create_node("the first element", "Ala");
	print_node(n);
	free_node(&n);

	n2 = create_node("the first element", "same key but different value");
	print_node(n2);
	free_node(&n2);

	
	return 0;
}