Memory leak in _conversionRulesFromUnit:toUnit:

[Tom Erik Støwer]

Instruments is reporting a memory leak in _conversionRulesFromUnit:toUnit: in HHUnitConverter.m here:

    NSMutableArray *rules = [NSMutableArray new];

The leak goes away when I change that line to:

    NSMutableArray *rules = [NSMutableArray array];

which creates an autoreleased array. I'm not sure if that's the root cause, but I can't find any other source.

I use the converter through a category:

#import "HHUnitConverter+Temperature.h"

@implementation HHUnitConverter (Temperature)

+ (HHUnitConverter *)sharedTemperatureConverter
{
    static HHUnitConverter *converter;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        converter = [HHUnitConverter new];
        [converter letUnit:@"C" convertToUnit:@"F" byMultiplyingBy:(9/5) andAdding:32];
    });
    return converter;
}

- (NSNumber *)fahrenheitFromCelsius:(NSNumber *)celsiusValue
{
    return [self value:celsiusValue.doubleValue convertedFromUnit:@"C" toUnit:@"F"];
}

- (NSNumber *)celsiusFromFahrenheit:(NSNumber *)fahrenheitValue
{
    return [self value:fahrenheitValue.doubleValue convertedFromUnit:@"F" toUnit:@"C"];
}

@end

I'd be happy to send a pull request on the fix, unless you think there is some other cause to the leak.

[Tom Erik Støwer]

More information on the leak. There are actually two leaks, one on the NSMutableArray object, but also one Malloc 16 bytes, that stems from this line:

    [rules addObject:[_weights objectForKey:routeStep.edge.name]];

[Andrei Iutkin]

What's the exact code that you use? I'm trying to reproduce the issue with this:

for (int i = 0; i < 100000; i++) {
    [[HHUnitConverter sharedTemperatureConverter] fahrenheitFromCelsius:@(30)];
}

but I can't see any leaks.

Also, do you have ARC on in your project?

[Andrei Iutkin]

I was able to reproduce the reported leaks when I turned off ARC.

HHUnitConverter is meant to be used with ARC only. If you can't use it for your entire project, you could flag HHUnitConverter.m with -fobjc-arc in build settings.

[Andrei Iutkin]

Closing it now. Feel free to reopen if needed.

[Tom Erik Støwer]

I am definately using ARC. Sorry I have not been able to respond. I will provide more debugging data tomorrow.

[Tom Erik Støwer]

Each call to a converter-method results in the two leaks: