指针在主不更新 [英] Pointer not updating in main
问题描述
我在另一个文件中调用一个函数主程序 cbuf_update()
这反过来又来电 cbuf_sizeChange()
这里是什么困惑我:在 cbuf_update
,要求 cbuf_sizeChange
正确更新 cb_ptr
,但main.c中,它是垃圾从我释放在 sizeChange()
。我不能让静态的,因为有主cbufs的变量数。我该怎么办?我不能改变的签名 cbuf_update()
。
结构体DEF:
typedef结构{CBUF
unsigned int类型最高;
无符号整型启动;
无符号整型结束;
unsigned int类型的大小;
报价*报价;
} CBUF;
从main.c中召唤:
CBUF * eur_jpy;
eur_usd = cbuf_init();
cbuf_update(eur_jpy,时间,速度);
在其他文件中的相关方法:
CBUF * cbuf_init()
{
//初始化使用malloc的CBUF 返回CB1;
}无效cbuf_update(CBUF * cb_ptr,双速率)
{
cb_ptr = cbuf_sizeChange(cb_ptr,2);
}CBUF * cbuf_sizeChange(CBUF * CB1,双因子)
{
CBUF * CB2;
报价*报价;
报价=(报价*)malloc的(cb1->最大* *因素的sizeof(报价));
CB2 =(CBUF *)malloc的(sizeof的(*引号)+ 4 * sizeof的(无符号整数)); //更新报价这里(exluding它) cb2->大小= cb1->大小;
cb2->结束= cb1->大小 - 1;
cb2->最大=系数* cb1->最大;
cb2->启动= 0;
免费(cb1->引号);
免费(CB1); cb2->报价=报价; 返回CB2;
}
这一点看起来不正确的:
无效cbuf_update(CBUF * cb_ptr,双速率)
{
cb_ptr = cbuf_sizeChange(cb_ptr,2);
}
它修改 cb_ptr
,这是一个本地副本无论你传递给 cbuf_update()
作为第一个参数
您可能想沿着这些线路认为:
无效cbuf_update(CBUF ** cb_ptr,双速率)
{
* cb_ptr = cbuf_sizeChange(* cb_ptr,2);
}
和,而不是调用 cbuf_update(什么东西,速度)
通话 cbuf_update。(安培;什么东西,速度)
I have a main program in another file calling a function cbuf_update()
that in turn calls cbuf_sizeChange()
Here is what is confusing me: Within cbuf_update
, calling cbuf_sizeChange
properly updates cb_ptr
, but in main.c, it is garbage from when I freed cb1 in sizeChange()
. I cannot make it static because there are a variable number of cbufs in main. What do I do? I cannot change the signature of cbuf_update()
.
Struct def:
typedef struct cbuf {
unsigned int max;
unsigned int start;
unsigned int end;
unsigned int size;
quote *quotes;
} cbuf;
Call from main.c:
cbuf *eur_jpy;
eur_usd = cbuf_init() ;
cbuf_update(eur_jpy, time, rate) ;
Relevant methods in other file:
cbuf * cbuf_init()
{
//initialize the cbuf with malloc
return cb1;
}
void cbuf_update(cbuf *cb_ptr, double rate)
{
cb_ptr = cbuf_sizeChange(cb_ptr, 2);
}
cbuf *cbuf_sizeChange(cbuf *cb1, double factor)
{
cbuf *cb2;
quote *quotes;
quotes = (quote *)malloc(cb1->max * factor * sizeof(quote));
cb2 = (cbuf *)malloc(sizeof(*quotes) + 4 * sizeof(unsigned int));
//Update quotes here(exluding it)
cb2->size = cb1->size;
cb2->end = cb1->size - 1;
cb2->max = factor * cb1->max;
cb2->start = 0;
free(cb1->quotes);
free(cb1);
cb2->quotes = quotes;
return cb2;
}
This bit doesn't look right:
void cbuf_update(cbuf *cb_ptr, double rate)
{
cb_ptr = cbuf_sizeChange(cb_ptr, 2);
}
It modifies cb_ptr
, which is a local copy of whatever you passed into cbuf_update()
as the first parameter.
You might want to think along these lines:
void cbuf_update(cbuf **cb_ptr, double rate)
{
*cb_ptr = cbuf_sizeChange(*cb_ptr, 2);
}
and instead of calling cbuf_update(something, rate)
call cbuf_update(&something, rate)
.
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