Memory alloc issues, crash on device iOS SDK 4.1(Thread 0 crash)

Question

I have two problems

1) My App works fine on the device the first few times its run. Then it crashes after the First screen pops up(Tab BAr). If i connect the device to my MAC and then run the device app it works(not debug mode).

I Checked the crash Logs, it crashed cos of "EXC_BAD_ACCESS (SIGSEGV)" and Thread0 crashed.The error was NSAutorelease released a deallocated Object.

2) I ran the app using instruments on the simulator. It show a lot of leaks on this function call. Here is a sample code. When i run it using Instruments it shows a leak on the "setObject" line.

//class A- subclass of NSObject

+(NSMutableDictionary *)Hello {

 NSMutableDictionary *dctONE = [[NSMutableDictionary alloc]initWithCapacity:0];
 NSMutableArray *arrKeys = [[NSMutableArray alloc] initWithCapacity:0];

    [arrKeys addObject:@"Object1"];
 [arrKeys addObject:@"Object2"];

    [dctONE setObject:[NSString stringWithFormat:@"dsfsdf"] forKey:[arrKeys          objectAtIndex:0]];
 [dctONE setObject:[NSString stringWithFormat:@"dsfsdf"] forKey:[arrKeys objectAtIndex:1]];

    [arrKeys release];
    return dctONE;

}

/// class B

-(void)some_Function {
 NSMutableDictionary * dct = [A Hello];   //all declarations are done

 //do stuff with dct
 [dct release];
}

WHy does it Leak at "setObject"?? I am releasing everything properly right? Only thing is the [NSString stringWithFormat:] but that is autorelease right??

This is driving me Crazy?

Are the two problems related?? PS: It Doesnt crash on the sim, and strangely doesnt crash even when i connect my device to my MAC and then test it on device(not debugging, directly clicking the app on the device)

EDIT:

-(NSMutableDictionary *) ExecuteDataSet:(NSString *)strQuery
{
    NSMutableDictionary  *dctResult = [[[NSMutableDictionary alloc] init] autorelease];
//  BOOL isSucess = FALSE;

const char *sql = [strQuery UTF8String];
sqlite3_stmt *selectStatement;

//prepare the select statement
int returnValue = sqlite3_prepare_v2(database, sql, -1, &selectStatement, NULL);
if(returnValue == SQLITE_OK)
{
    sqlite3_bind_text(selectStatement, 1, sql, -1, SQLITE_TRANSIENT);
    //loop all the rows returned by the query.
    NSMutableArray *arrColumns = [[NSMutableArray alloc] init];
    for (int i=0; i<sqlite3_column_count(selectStatement); i++) 
    {
        const char *st = sqlite3_column_name(selectStatement, i);
        [arrColumns addObject:[NSString stringWithCString:st encoding:NSUTF8StringEncoding]];
    }
    int intRow =1;
    while(sqlite3_step(selectStatement) == SQLITE_ROW)
    {
        NSMutableDictionary *dctRow = [[NSMutableDictionary alloc] init];
        for (int i=0; i<sqlite3_column_count(selectStatement); i++)                 
        {
            int intValue = 0;
            const char *strValue;
            switch (sqlite3_column_type(selectStatement,i)) 
            {
                case SQLITE_INTEGER:
                    intValue  = (int)sqlite3_column_int(selectStatement, i);
                    [dctRow setObject:[NSString stringWithFormat:@"%d",intValue] forKey:[arrColumns objectAtIndex:i]];                      
                    break;

                case SQLITE_TEXT:
                    strValue = (const char *)sqlite3_column_text(selectStatement, i);
                    [dctRow setObject:[NSString stringWithCString:strValue encoding:NSUTF8StringEncoding] forKey:[arrColumns objectAtIndex:i]];                     
                    break;

                default:
                    strValue = (const char *)sqlite3_column_value(selectStatement, i);
                    [dctRow setObject:[NSString stringWithCString:strValue encoding:NSUTF8StringEncoding] forKey:[arrColumns objectAtIndex:i]];
                    break;
            }

        }
        [dctResult setObject:[dctRow retain] forKey:[NSString stringWithFormat:@"Table%d",intRow]];
        intRow ++;
        [dctRow release];
    }
    [arrColumns release];
}
return dctResult;

}

Answer 1

The leak appears to be in this line:

[dctResult setObject:[dctRow retain] forKey:[NSString stringWithFormat:@"Table%d",intRow]];

setObject will call retain on the object it stores, but you are actually retaining it manually, so its retain count will be 2 instead of 1, and when dctResult gets released, it won't be removed from memory.

Answer 2

You're doing a whole bunch of unnecessary work in +Hello. My first step at debugging is always to remove unnecessary complexity. Try it like this:

+(NSMutableDictionary *)Hello {

     NSMutableDictionary *dctONE = [NSMutableDictionary dictionaryWithObjectsAndKeys:
         @"dsfsdf", @"Object1", @"dsfsdf", @"Object2", nil];

     return dctONE;
}

That NSMutableDictionary dictionaryWithObjectsAndKeys method takes a nil-terminated array that goes object, key, object, key. It returns an autoreleased NSMutableDictionary object, which is what you want to be returning.

There are no guarantees in this world, but I can darn near promise you that method won't leak.