Invalid initializer compiler-error at malloc of struct array

Question

I'm trying to read an arbitrary number of string items into an array of structs when my program initializes. I want to allocate heap memory for the

When the compiler gets to the following line, it throws an error: invalid initializer.

The first part of my code:

int main() {
    printf("Work starts in the vineyard.\n");

    typedef struct {
        char* name[20];
        unsigned int jobs;
    }Plantation;

    // read from list of plantations
    FILE  *plantationFile = fopen("./data/plantations.txt", "r");
    if (plantationFile==NULL) {perror("Error opening plantations.txt."); exit(1);}

    char line[20];
    char *lp = line;
    int plantationCount;
    Plantation plantations[] = (Plantation *)malloc(sizeof(Plantation));
    if (!feof(plantationFile)) {
        int i = 0;
        fgets(line, 20, plantationFile);
        scanf(lp, "%i", &plantationCount);
        realloc(plantations, sizeof(Plantation) * plantationCount);
        while( !feof(plantationFile) ) {
            fgets(line, 20, plantationFile);
            strcpy(*(plantations[i].name), lp);
            plantations[i].jobs = 1u;
            ++i;
        }
    }
...

What am I missing here?

The compiler output:

$ gcc -W -Wall vineyard.c
vineyard.c: In function ‘main’:
vineyard.c:30:32: error: invalid initializer
     Plantation plantations[] = (Plantation *)malloc(sizeof(Plantation));
                                ^

It also throws the same if I leave out typecasting.

$ gcc -W -Wall vineyard.c
vineyard.c: In function ‘main’:
vineyard.c:30:32: error: invalid initializer
     Plantation plantations[] = malloc(sizeof(Plantation));
                                ^~~~~~

Thanks!

dbush · Accepted Answer · 2020-04-29 20:53:22Z

2

You're defining plantations as an array, and you're trying to initialize an array with a pointer. An initializer for an array must be a brace enclosed list of initializers. More importantly, while arrays and pointers are related, they are not the same thing.

Define plantations as a pointer instead of an array:

Plantation *plantations = malloc(sizeof(Plantation));

Also, realloc can change where the allocated memory points to, so you need to assign the return value back:

plantations = realloc(plantations, sizeof(Plantation) * plantationCount);

You should also check the return value of malloc and realloc for errors.

answered Apr 29, 2020 at 20:53

dbush

233k27 gold badges261 silver badges334 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Bundologus Over a year ago

Okay, I see what you mean. The malloc function's return type is pointer, and I'm trying to assign that to an array type variable. I guess I got confusedIf I keep plantations as a pointer, will I be able to use the plantations[i] syntax, or am I limited to pointer arithmetic? If so, is there a way I can use the [ ] syntax?

dbush Over a year ago

@Bundologus Yes, *(A + B) is exactly equivalent to A[B].

Collectives™ on Stack Overflow

Invalid initializer compiler-error at malloc of struct array

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related