在动态结构数组中使用realloc [英] Using realloc in dynamic structure array
问题描述
我正在尝试使用realloc动态创建结构实例,并在进行时用临时结构中的数据填充它.当程序再次到达要再次分配该结构的指针的行时,程序崩溃,但是我不确定如何构造该函数.我有以下代码:
I am trying to use realloc to dynamically create instances of a struct, filling it with data from a temporary structure as I go. The program crashes when it reaches the line to malloc a pointer of the structure a second time but I am not sure how I should structure this function. I have the following code:
#define MAX_STRING 50
struct data {
int ref;
int port;
char data[MAX_STRING+1];
}valid, invalid;
void read_file(FILE *file);
void validate(struct data* temp);
int g = 0;
int main(){
char inputfile[100];
FILE *file = fopen("file.txt" , "r");
if (file != NULL){
read_file (file);
}
else{
// Some code here..
}
return 0;
}
void read_file(FILE *file){
struct data* temp = malloc(sizeof(struct data));
char buf[1024];
while(!feof(file)){
fgets(buf, sizeof buf, file))
sscanf(buffer, "%d.%d.%s", &temp->ref, &temp->port, &temp->data);
validate(temp);
g++;
}
}
void validate(struct data* temp){
if((some condition) && (some condition))
{
create_valid(temp);
}
if((some condition) && (some condition))
{
create_invalid(temp);
}
}
我不确定如何构造以下功能:
I am unsure of how to structure the following function:
int create_vaild(struct data* temp){
struct data* valid = malloc(sizeof(struct data)); <<<<<<<<< Line that crashes
valid = realloc(valid, g * sizeof(struct data));
valid[g] = *temp;
if (valid[g] == NULL){
//error.
};
printf("\n%i:%i:%s\n", (valid+g)->ref, (valid+g)->port, (valid+g)->data);
return 0;
}
推荐答案
我看到一个潜在的问题:
I see one potential problem:
您将g设置为0,即
int g =0;
在调用create_valid()
之前不会增加它.您正在使用此值在该函数内部分配内存:
You are not incrementing it before the call to create_valid()
. You are using this value to allocate memory inside that functions:
valid = realloc(valid, g * sizeof(struct data));
所以现在g
是0
.
稍后在下一行中取消引用此指针
Later in the next line you dereference this pointer
valid[g] = *temp;
这是您尚未分配的一些内存,因为realloc()
没有为您分配内存,因为您向其传递了0.因此崩溃.
This is some memory which you have not allocated as realloc()
didn't allocate memory for you becasue you passed 0 to it.Hence the crash.
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