指向结构的指针 [英] pointers to structures
问题描述
我在这里有点困惑，没有编程一段时间。任何帮助
都会感激不尽。
如果我定义了几个结构：
struct sfinfo {
双倍srate;
短ssize;
短期支票;
};
typedef struct {
void * pRawBuf;
FILE * fp;
struct sfinfo info;
} SOUNDFILE;
和函数如此：
void sfinfocopy（struct sfinfo * from，struct sfinfo * to）{
to-> srate = from-> srate;
to-> ssize = from-> ssize;
to-> chans = from-> chans;
}
如果我这样做：
blah（struct sfinfo * info）{
SOUNDFILE * outsfp;
outsfp = （SOUNDFILE *）malloc（sizeof（SOUNDFILE）））== NULL;
sfinfocopy（info，&（outsfp-> info））;
}
它没有'似乎工作。表达式&（outsfp-> info）是不对的，是吗？
Robert
I am a bit confused here, having not programmed for some time. Any help
would be gratefully received.
If I define a couple of structures thus:
struct sfinfo {
double srate;
short ssize;
short chans;
};
typedef struct {
void *pRawBuf;
FILE *fp;
struct sfinfo info;
} SOUNDFILE;
and a function so:
void sfinfocopy(struct sfinfo *from, struct sfinfo *to) {
to->srate = from->srate;
to->ssize = from->ssize;
to->chans = from->chans;
}
If I then do something like this:
blah(struct sfinfo *info) {
SOUNDFILE *outsfp;
outsfp = (SOUNDFILE *)malloc(sizeof(SOUNDFILE)))==NULL;
sfinfocopy(info, &(outsfp->info));
}
It doesn''t seem to work. The expression &(outsfp->info) isn''t right, is it?
Robert
推荐答案
以下编译对我来说很好：
#include< stdio.h>
struct sfinfo {
双倍srate;
短ssize;
短期chans;
};
typedef struct {
void * pRawBuf;
FILE * fp;
struct sfinfo info;
} SOUNDFILE;
void sfinfocopy（struct sfinfo * from，struct sfinfo * to）{
to-> srate = from-> srate;
to-> ssize = from-> ssize;
to-> chans = from-> chans;
}
blah（struct sfinfo * info）{
SOUNDFILE * outsfp;
outsfp =（SOUNDFILE *）malloc（sizeof（SOUNDFILE））; / *删除错误* /
sfinfocopy（info，&（outsfp-> info））;
}
int main（无效）
{
struct sfinfo obj = {0};
blah（& obj）;
}
-
Frederick Gotham
The following compiles just fine for me:
#include <stdio.h>
struct sfinfo {
double srate;
short ssize;
short chans;
};
typedef struct {
void *pRawBuf;
FILE *fp;
struct sfinfo info;
} SOUNDFILE;
void sfinfocopy(struct sfinfo *from, struct sfinfo *to) {
to->srate = from->srate;
to->ssize = from->ssize;
to->chans = from->chans;
}
blah(struct sfinfo *info) {
SOUNDFILE *outsfp;
outsfp = (SOUNDFILE *)malloc(sizeof(SOUNDFILE)); /* Remove ERROR */
sfinfocopy(info, &(outsfp->info));
}
int main(void)
{
struct sfinfo obj = {0};
blah(&obj);
}
--
Frederick Gotham
R Dow写道：
R Dow wrote:
blah（struct sfinfo * info）{
SOUNDFILE * outsfp;
outsfp =（SOUNDFILE *）malloc（sizeof（SOUNDFILE）））== NULL;
sfinfocopy（info，&（outsfp- > info））;
}
它似乎无法奏效。表达式&（outsfp-> info）不对，是吗？
blah(struct sfinfo *info) {
SOUNDFILE *outsfp;
outsfp = (SOUNDFILE *)malloc(sizeof(SOUNDFILE)))==NULL;
sfinfocopy(info, &(outsfp->info));
}
It doesn''t seem to work. The expression &(outsfp->info) isn''t right, is it?
不，没关系。这是你的malloc系列。
1.不要回复[提示：包括stdlib.h]
2.使用sizeof（* outfp）作为里面的大小
3.什么是== NULL应该做什么？
4.在malloc之后添加一个if语句来检查NULL
Tom
No it''s fine. It''s your malloc line.
1. Don''t cast return [hint: include stdlib.h]
2. use sizeof( *outsfp ) as the size inside
3. What is ==NULL supposed to do?
4. Add an if statement after the malloc to check for NULL
Tom
Frederick Gotham发布：
Frederick Gotham posted:
outsfp =（SOUNDFILE *）malloc（sizeof（SOUNDFILE））;
outsfp = (SOUNDFILE *)malloc(sizeof(SOUNDFILE));
#include< stdlib.h>
-
Frederick Gotham
#include <stdlib.h>
--
Frederick Gotham
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