CODEWITHSUNDEEP
objective-cmemory-managementnsstringautoreleasedealloc
Robert
Robert

Reputation: 13

NSString alloc outside autorelease pool creates mysterious memory leak?

the following error is produced at runtime when manually allocating and releasing memory:

objc[10430]: Object 0x109014b60 of class __NSCFData autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug

I searched the internet but usually these errors are caused by not releasing memory or using autoreleased shorthands... I cannot find any unreleased memory, nor am I using an autoreleased shorthand... Hoping you can help!

My code is:

#import "try.h"

@implementation try

- (try*)initWithSwing
{
    self = [super init];
    if (self) {
        [self tellAboutSwing:YES];
    }

    return self;
}

- (void) tellAboutSwing: (BOOL) swing {

    NSString *s = [[NSString alloc] initWithFormat: @"%@ %@", @"Do we have a swing on our playground?", (swing ? @"Yes" : @"No")];


    // cast to a char
    const char *c = [s UTF8String];
    [s release];    
    printf("%s", c);

}

- (void) dealloc {
    printf( "Deallocing Playground\n" );
    [super dealloc];
}

int main(void) {
    try *t;
    t = [[try alloc] initWithSwing];
    [t release];
}

@end

Putting an autorelease pool inside the instance method fixes the issue, but that shouldn't be necessary with NSString alloc. While I am new to Objective-C I think I have grasped the concept of owning and releasing variables, yet I am having difficulty finding my error here.

Here's my .h file:

#include <Foundation/Foundation.h>


@interface try : NSObject
- (void) tellAboutSwing: (BOOL) swing;
@end

Help would be greatly appreciated :)

Regards,

Robert

Upvotes: 1

Views: 672

Answers (2)

CodeStage
CodeStage

Reputation: 540

You should just use an NSAutoreleasePool. It's normal to have one and at some point you won't find an alternative which is not creating autoreleased objects internally.

I think you should check out some tutorials and guides on memory management and the basics, otherwise you will have a hard time understaning Objective-C.

For example, there is a great course on iTunesU which is free and explains the basics of Objective-C.

Upvotes: 1

Wevah
Wevah

Reputation: 28242

IIRC -[NSString UTF8String] uses an autoreleased NSData to actually hold the bytes of the UTF-8 C string.

Update: Here's a simpler way using just C functions:

- (void) tellAboutSwing: (BOOL) swing {    
    printf("%s %s", "Do we have a swing on our playground?", (swing ? "Yes" : "No"));
}

Upvotes: 5

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