crash at [NSFileManager removeItemAtPath:error:]

Question

I am trying to remove a file from path using following code. But my application is crashing while removing file from the path.

- (void)saveEditedSavedFile:(NSString*)editedfile As:(NSString*)originalFile
{
    [originalFile retain];
    NSArray* dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString* docsDir = [dirPaths objectAtIndex:0]; 

    NSError* error = nil;

    NSString *editedFilePath=[docsDir stringByAppendingPathComponent:editedfile];

    NSFileManager* fileMngr = [NSFileManager defaultManager];

    if([fileMngr fileExistsAtPath:originalFile])
    {
nslog(@"%@", originalFile); // nslog always prints the correct path even if it crashes..
        [fileMngr removeItemAtPath:originalFile error:NULL];
    }

    if ([fileMngr moveItemAtPath:editedFilePath toPath:originalFile error:&error] != YES)
    {
        UIAlertView* alertView1 = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Unable to Save File. Please Choose a Diffrent name." delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];
        [alertView1 show];
        [alertView1 release];

    }

}

Here i am trying to replace an already existing file with a new file.(Moving a file operation) but it crashes at [fileMngr removeItemAtPath:originalFile error:NULL];

I am getting a call stack like this ..

#0  0x99f1dc5a in __kill ()
#1  0x99f1dc4c in kill$UNIX2003 ()
#2  0x99fb05a5 in raise ()
#3  0x99fc66e4 in abort ()
#4  0x99fb4e78 in szone_error ()
#5  0x99fb4fb3 in free_list_checksum_botch ()
#6  0x99ec7a88 in small_free_list_remove_ptr ()
#7  0x99ec45cc in szone_free_definite_size ()
#8  0x99ec35e8 in free ()
#9  0x99ee8adb in fts_close$INODE64 ()
#10 0x99f31b57 in __removefile_tree_walker ()
#11 0x99f31999 in removefile ()
#12 0x0006ed01 in -[NSFilesystemItemRemoveOperation main] ()
#13 0x0005cbd2 in -[__NSOperationInternal start] ()
#14 0x0006eaa2 in -[NSFileManager removeItemAtPath:error:] ()

can anyone let me know why my application is crashing? i checked that that path is coming as correct there.

Answer 1

Best guess is that originalFile has been over released and at some point during the execution of -removeItemAtPath:error: its memory has been reallocated. Try running it with the zombies profiling tool.

Answer 2

The stack trace looks like there's an implementation error in NSFileManager .

The functions that do the dirty work of deleting (nested) files ( remove file and __removefile_tree_walker ) use BSD's "fts" facility (see man fts ) to walk the directory structure. In the latter function an FTS handle gets closed that is not open. This is definitely a bug in the implementation. You should file a radar .

How that can happen is a matter of guessing. I'd look in the direction of concurrent operations on the filesystem (parallel deletion on the same item, moving part of the hierarchy while it gets deleted, ...).