问题
I'm trying to implement an replacement algorithm that deals with page faults. So i'm trying to creat a circular linked list using malloc and im getting the following error: "invalid application of sizeof' to incomplete type
pageInMemory'.following is the code:
typedef struct {
int use;
int reference;
int free;
struct pageInMemory* next;
} pageInMemory;
int main()
{
int i;
struct pageInMemory* start, *nn, *temp, *hand;
start = NULL;
for(i=0; i< pNum; i++)
{
nn = (struct pageInMemory *)malloc(sizeof(struct pageInMemory));
nn->use = 0;
nn->free = 1;
if(start==NULL)
{
nn->next = nn;
start =nn;
}
else
{ // sfhsdifhsdifj sdijfjsd
temp = start;
while(temp->next != start)
{
temp = temp->next;
}
temp->next = nn;
nn->next = start;
start = nn;
}
}
hand = start;
temp = start;
while(temp->next != start->next)
{
printf("%d\n", temp->use); //hi
}
return 0;// bye
}
so am i not supposed to use malloc this way ?
回答1:
change your struct definition as
struct pageInMemory{
int use;
int reference;
int free;
struct pageInMemory* next;
};
to get your code working. And just for your info do not typecast void* coming from malloc.
回答2:
pageInMemory
is itself defined as type. So instead of this,
nn = (struct pageInMemory *)malloc(sizeof(struct pageInMemory))
Use this,
nn = (pageInMemory *)malloc(sizeof(pageInMemory))
回答3:
It should be either:
typedef struct pageInMemory_s {
int use;
int reference;
int free;
struct pageInMemory_s * next;
} pageInMemory;
pageInMemory* start, *nn, *temp, *hand;
...
nn = malloc(sizeof(pageInMemory));
or
struct pageInMemory {
int use;
int reference;
int free;
struct pageInMemory* next;
};
struct pageInMemory* start, *nn, *temp, *hand;
...
nn = malloc(sizeof(struct pageInMemory));
A third variant would be:
typedef struct pageInMemory {
int use;
int reference;
int free;
struct pageInMemory * next;
} pageInMemory;
pageInMemory* start, *nn, *temp, *hand;
...
For this 3rd option you can use:
nn = malloc(sizeof(pageInMemory));
or
nn = malloc(sizeof(struct pageInMemory));
This latter variation I feel is very irritating as there is one name for two different things:
- The structure definition/declaration
struct pageInMemory
- The type definition/declaration
pageInMemory
I would not recommend to use this 3rd option, but the second.
来源:https://stackoverflow.com/questions/17211345/invalid-application-of-sizeof-to-incomplete-type-list-struct-c