The left operand of '==' is a garbage value

Question

I am getting this error when I analize my ios project

The left operand of '==' is a garbage value

this is what the code looks like where its occurring.. This method is used to sort the array I have that is returned to me from the DB.

- (NSMutableArray *)startSortingTheArray:(NSMutableArray *)unsortedArray
{
    [unsortedArray sortUsingComparator:^ NSComparisonResult(SearchResultItem *d1, SearchResultItem *d2) {
        //initalize comparison
        NSComparisonResult result;

        NSInteger manufacturerID1 = d1.manufacturerID;
        NSInteger manufacturerID2 = d2.manufacturerID;
            if (manufacturerID1 > manufacturerID2)
                return NSOrderedAscending;
            if (manufacturerID1 < manufacturerID2)
                return NSOrderedDescending;
            if (manufacturerID1 == manufacturerID2) {

            NSString *model1 = d1.model;
            NSString *model2 = d2.model;
            result = [model1 localizedCompare:model2];
        }
        if (result == NSOrderedSame) {
//..

score 5 · Accepted Answer · answered Oct 11 '12 at 20:42

The compiler is complaining because it believes it's possible to reach the == comparison before result has a value.

The best option given your code is to use else if and else:

if (manufacturerID1 > manufacturerID2)
    return NSOrderedAscending; // we won't reach the comparison so result doesn't matter
else if (manufacturerID1 < manufacturerID2)
    return NSOrderedDescending; // we won't reach the comparison so result doesn't matter
else {
    NSString *model1 = d1.model;
    NSString *model2 = d2.model;
    result = [model1 localizedCompare:model2]; // in any other case, result will be set.
}
...

Or you could do this:

NSComparisonResult result;
...
if (manufacturerID1 > manufacturerID2)
    return NSOrderedAscending;
else if (manufacturerID1 < manufacturerID2)
    return NSOrderedDescending;

NSString *model1 = d1.model;
NSString *model2 = d2.model;
result = [model1 localizedCompare:model2];
...

Or even this:

if (manufacturerID1 > manufacturerID2)
    return NSOrderedAscending;
else if (manufacturerID1 < manufacturerID2)
    return NSOrderedDescending;

NSComparisonResult result = [d1.model localizedCompare:d2.model];
...

This way the compiler knows that if the comparison is reached, the value of result will already have been set.

Cool this worked perfectly! will mark your answer once the time is up... thanks a bunch — HurkNburkS, Oct 11 '12 at 20:42

score 0 · Answer 2 · answered Oct 11 '12 at 20:43

I think it's just the llvm “solver” not understanding that precisely one of <, >, or == must be true in relation to the manufacturerID[12] comparisons. Try removing the if (manufacturerID1 == manufacturerID2) block, so that it can tell that the value of result isn't being used uninitialized. Despite your comment, you don't actually initialize its value, there.

The left operand of '==' is a garbage value

2 Answers2