I have a struct defined as:
struct {
char name[32];
int size;
int start;
int popularity;
} stasher_file;
and an array of pointers to those structs:
struct stasher_file *files[TOTAL_STORAGE_SIZE];
In my code, I'm making a pointer to the struct and setting its members, and adding it to the array:
...
struct stasher_file *newFile;
strncpy(newFile->name, name, 32);
newFile->size = size;
newFile->start = first_free;
newFile->popularity = 0;
files[num_files] = newFile;
...
I'm getting the following error:
error: dereferencing pointer to incomplete type
whenever I try to access the members inside newFile
. What am I doing wrong?
This question is related to
c
struct
dereference
the case above is for a new project. I hit upon this error while editing a fork of a well established library.
the typedef was included in the file I was editing but the struct wasn't.
The end result being that I was attempting to edit the struct in the wrong place.
If you run into this in a similar way look for other places where the struct is edited and try it there.
The reason why you're getting that error is because you've declared your struct
as:
struct {
char name[32];
int size;
int start;
int popularity;
} stasher_file;
This is not declaring a stasher_file
type. This is declaring an anonymous struct
type and is creating a global instance named stasher_file
.
What you intended was:
struct stasher_file {
char name[32];
int size;
int start;
int popularity;
};
But note that while Brian R. Bondy's response wasn't correct about your error message, he's right that you're trying to write into the struct
without having allocated space for it. If you want an array of pointers to struct stasher_file
structures, you'll need to call malloc
to allocate space for each one:
struct stasher_file *newFile = malloc(sizeof *newFile);
if (newFile == NULL) {
/* Failure handling goes here. */
}
strncpy(newFile->name, name, 32);
newFile->size = size;
...
(BTW, be careful when using strncpy
; it's not guaranteed to NUL-terminate.)
How did you actually define the structure? If
struct {
char name[32];
int size;
int start;
int popularity;
} stasher_file;
is to be taken as type definition, it's missing a typedef
. When written as above, you actually define a variable called stasher_file
, whose type is some anonymous struct type.
Try
typedef struct { ... } stasher_file;
(or, as already mentioned by others):
struct stasher_file { ... };
The latter actually matches your use of the type. The first form would require that you remove the struct
before variable declarations.
You are using the pointer newFile
without allocating space for it.
struct stasher_file *newFile = malloc(sizeof(stasher_file));
Also you should put the struct name at the top. Where you specified stasher_file is to create an instance of that struct.
struct stasher_file {
char name[32];
int size;
int start;
int popularity;
};
Source: Stackoverflow.com