Declaring an array with an integer

[rpalmer]

Hi,
I want to create an array based on the result from a mysql query.

ie.

int num_to_create;

struct ftp_details {
	char *host;
	char *userpass;
	char *options;
	long sid;
	long fid;
};

num_to_create = mysql_num_rows(res); // returns 1

struct ftp_details ftpdetails_array[num_to_create];

Later in program i get a segfault by code trying to use the array, however i can fix it by changing the code to

struct ftp_details ftpdetails_array[1];

So is it possible to declare an array with an integer?

Thanks,

[MacGyver]

It's permissible to do that if you are using a compiler that follows the C99 standard with that regard. If you are using a C89 compiler, it is not allowed.

I would not recommend doing it, however. In a case like this, I would malloc() the needed memory. Memory allocated via malloc() comes from the heap while memory allocated like you are doing it comes from the stack. Stack sizes are usually limited, and there is no real way to check if you blew your limit. If you attempt to allocate memory from the heap, at least you'll be in a position to recover if the memory allocation fails.

[rpalmer]

Ok Thanks.

So to use malloc, I would have to change my char pointers to fixed length arrays?

ie.

struct ftp_details {
	char host[200];
	char userpass[100];
	char options[50];
	long sid;
	long fid;
};

[robatino]

Also, most compilers haven't fully implemented C99 yet, so until that happens it's probably a good idea to try to write code that complies with both C89 and C99, which in particular means not using C99-specific features.

[MacGyver]

No, you don't have to change them to fixed length arrays. If they are pointers, you can malloc() them as well, depending upon how long they need to be.