Question

in a project using garbage collection:
Clang alerts ‘Potential null dereference….’ on line assigning *anError.

But this look right to me according to: Why does NSError need double indirection? (pointer to a pointer)

Can anyone see what i’m not seeing ?

- (NSData *)bookmarkDataForCurrentURL:(NSURL *)theURL error:(NSError **)anError
{
    NSArray *bkKeys = [CBPrepCommon bookmarkPropertyKeys];
    NSError *errorA = nil;
    NSData *bkmark = [theURL bookmarkDataWithOptions:NSURLBookmarkCreationPreferFileIDResolution includingResourceValuesForKeys:bkKeys relativeToURL:nil error:&errorA];

    if (![bkmark length] > 0) {
    if (errorA) {
        // error here
        *anError = [NSError errorWithDomain:[errorA domain] code:[errorA code] userInfo:[errorA userInfo]];
    }
    return nil;
}
return bkmark;

}

Answer 1

if (errorA && anError) {
    // error here
    *anError = [NSError errorWithDomain:[errorA domain] code:[errorA code] userInfo:[errorA userInfo]];
}

EDIT: Even cleaner:

- (NSData *)bookmarkDataForCurrentURL:(NSURL *)theURL error:(NSError **)anError
{
    NSArray *bkKeys = [CBPrepCommon bookmarkPropertyKeys];
    NSData *bkmark = [theURL bookmarkDataWithOptions:NSURLBookmarkCreationPreferFileIDResolution includingResourceValuesForKeys:bkKeys relativeToURL:nil error:anError];

    if ([bkmark length] == 0) {
        return nil;
    }

    return bkmark;
}