access violation error

[Koroskin Denis]

On Thu, 14 Aug 2008 01:23:05 +0400, Wyverex <wyverex.cypher at gmail.com>  
wrote:

> Michael P. wrote:
>> /* junior304.d
>> 2008 junior problem 3
>> Smile with similies
>> Ask for 2 numbers; the number of adjectives and nouns
>> After you get the numbers and nouns and adjectives, out all possible  
>> similies
>> August 12th, 2008 */
>>  //Imports
>> import std.stdio;
>>  /*****
>> *Main*
>> *****/
>> void main()
>> {
>> 	int numberOfAdjectives;
>> 	scanf( "%d", &numberOfAdjectives );
>> 	int numberOfNouns;
>> 	scanf( "%d", &numberOfNouns );
>> 	
>> 	char[][] adjectives; //array of strings to hold the adjectives
>> 	adjectives.length = 6; //max number that user enters is 5, 6 to be  
>> safe 	char[][] nouns; //same as above, but for nouns
>> 	nouns.length = 6; //same as adjectives reason
>> 	
>> 	//get adjectives first
>> 	for ( int i = 0; i < numberOfAdjectives; i++ ) //get the specified #  
>> of adjectives
>> 	{
>> 		scanf( "%s", &adjectives[ i ] );
>> 	}
>> 	
>> 	//now get the # of nouns specified
>> 	for ( int i = 0; i < numberOfNouns; i++ )
>> 	{
>> 		scanf( "%s", &nouns[ i ] );
>> 	}
>> 	
>> 	//print out all possible similies
>> 	for ( int i = 0; i < numberOfAdjectives; i++ )
>> 	{
>> 		for ( int j = 0; j < numberOfNouns; j++ )
>> 		{
>> 			//for every adjective, place a noun after and turn it into a similie
>> 			writefln( "%s as %s", adjectives[ i ], nouns[ j ] );
>> 		}
>> 	}
>> }
>>   I get an accessviolation when I enter the last 2 for loops; any  
>> reason why?
>>  Input is:
>> 3
>> 2
>> Easy
>> Soft
>> Smart
>> pie
>> rock
>>  error!
>
Your code is seriously broken!

The following line is wrong, for example:
> scanf( "%s", &nouns[ i ] );

What are you doing here? Are you out of your mind? You are passing a  
pointer to a char[]* to a function that accept a char*. Your array will be  
overwritten with whatever you will type. It is wrong, wrong, wrong!

I think that you don't understand something. First of all, what is a  
char[]? It is a struct that consists of a array size and a pointer:

struct CharArray {
    size_t size;
    char* ptr;
}

typeof(nounts[i]) is a char[], typeof(&nouns[i]) is char[]*. You pass this  
pointer to a function that accepts a pointer to a preallocated buffer for  
a string to be written to.

A quick fix would be to:
1) allocate a buffer:
nouns[i] = new char[64];
2) pass a pointer to the preallocated buffer:
scanf("%s", nouns[i].ptr);

A good fix would be to use readf instead. I didn't use it, but this should  
be sufficient:
readf("%s", &nouns[i]);


> quick fix is to use printf
> printf( "%s as %s", &adjectives[ i ], &nouns[ j ] );
>
> i think (not sure don't really use phobos that much) scanf doesn't  
> return strings in a format writef likes...
>
> I though theres a readf but cant find documentation on it...

Test before posting, please!