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判斷棧的增長方向
dreamhead老大曾經討論過這個問題，尋找一種可移植的方式來判斷棧的增長方向，見《棧的增長方向》。今天在讀Ruby hacking guide第5章，介紹alloca函數的部分，提到ruby實現的C語言版本的alloca.c，讀了下代碼，發現這裏倒是實現了一個很漂亮的函數用於實現判斷棧的增長方向，利用了局部static變量，與dreamhead老大的想法其實是一致的。
#include<stdio.h>
static void find_stack_direction(void);
static int stack_dir;
int main(void)
{
find_stack_direction();
if(stack_dir==1)
puts("stack grew upward");
else
puts("stack grew downward");
return 0;
}
static void find_stack_direction (void)
{
static char *addr = NULL; /* address of first
`dummy', once known */
auto char dummy; /* to get stack address */
if (addr == NULL)
{ /* initial entry */
addr = &dummy;
find_stack_direction (); /* recurse once */
}
else /* second entry */
if (&dummy > addr)
stack_dir = 1; /* stack grew upward */
else
stack_dir = -1; /* stack grew downward */
}
static void find_stack_direction(void);
static int stack_dir;
int main(void)
{
find_stack_direction();
if(stack_dir==1)
puts("stack grew upward");
else
puts("stack grew downward");
return 0;
}
static void find_stack_direction (void)
{
static char *addr = NULL; /* address of first
`dummy', once known */
auto char dummy; /* to get stack address */
if (addr == NULL)
{ /* initial entry */
addr = &dummy;
find_stack_direction (); /* recurse once */
}
else /* second entry */
if (&dummy > addr)
stack_dir = 1; /* stack grew upward */
else
stack_dir = -1; /* stack grew downward */
}
文章轉自莊周夢蝶 ，原文發布時間2007-09-17
最後更新：2017-05-18 10:32:52