Developing Public Safety Technology in Suffolk's Rural Heartland
Tom Fosdick
Tom Fosdick is a software architect whose experience ranges from low level coding through to product management, delivery and customer relationships.
For nearly 20 years Tom has specialised in providing advanced technology to front line Emergency Services both in the UK and internationally.
The Cat’s Favourite Spot on a Dark Morning.Something struck me yesterday. Something Evil. It comes out of the fact that you can use C#’s Null-Coalescing operator – that’s ?? to most people – with reference types as well as nullable (value) types.
Most C# devs I dare say will be familiar with C#’s nullable types. They’re really System.Nullable<T> but C# allows you to use the nice shortcut of just putting a ? after the type declaration…
class ExampleClass
{
int? exampleField;
System.Nullable<int> isTheSameAsExampleField;
}
You quite often see ?? used with examples of nullable types but it can actually be used with any reference type too. String is the most obvious[1]. For instance there’s a very common gotcha of performing some operation on a string that could actually be null. For instance,
if(someObject.someString.Contains("SOME TEXT"))
{
If someString is NULL (as opposed to "") this will throw a NullReferenceException
Note that although the logical result of these two options is the same the way it accomplishes that result is subtly different. In the first example if the string is null the Contains will never be executed. In the second it will be executed against the "" object (which clearly doesn’t contain "SOME TEXT"). The result in both cases is that the if condition as a whole evaluates to false, but it does so for different reasons.
…and so now here’s a way you can use these powers for evil. Let’s say you need to add something to a list, the problem is that you don’t know if the list has been instantiated yet, but if it hasn’t you need to instantiate it. This type of situation actually happens quite a lot and this solution works, ho-hum.
List<string> list = null;
...some code...
(list ?? (list = new List<string>()) ).Add("blah");
It works because C#’s assignment operator (single =) produces a result, the result is the value that was assigned. So this code says "if list is instantiated then use it for the Add. If not then instantiate a new List<string> and assign the value to list then take the result of that assignment (the newly instantiated object) and use that for the Add".
In summary then, you can use ?? against any type that could have a null value, not just System.Nullable<T>, but be careful with it because it’s a power than can be easily abused.
[1] string is actually a reference type, but it behaves like a value type
An accidental feature has just bitten us in the butt. I thought it worth a quick mention because it’s one of those things that happens quite often in the software industry and it’s more complex than it might first appear.
In this case it’s the ordering of a list – the customer had noticed that the list was always in a particular order. They wrote their training notes and indeed their operational procedures based around the fact that this list was always in that order.
We didn’t explicitly program the list to be in that order, we didn’t declare it as a feature that it’d be in that order, nevertheless it so happened that it was. Then we fixed a bug and as a result the ordering of the list changed slightly.
Now we have a bug report complaining that we’ve broken the list.
There are certain elements of the software development world that now would be waving their in-depth specifications at us crowing about how bad Agile is at this kind of thing and how if we’d “done it properly” then it would have been clear from the start that the list was in no guaranteed order.
They would be mockingly waving those specification documents if a) they could move them without a fork-lift and b) they hadn’t been put out of business years ago by Agile software houses like Seed.
Would it really have helped though? Perhaps – maybe the customer wouldn’t have relied on the ordering of the list or maybe they’d have spotted that it wasn’t ordered and asked for a change in the specification before the initial delivery.
Actually that isn’t so likely. Such specifications are often so complex and confusing that they never get much distribution within the customer organisation and if they do the number of people who understand them is limited (often to zero). The likelihood that the people who needed to know that the list was not in a guaranteed order actually knowing this is rather far from 100%.
Naturally there is also the risk that no matter how detailed the specification that particular detail was omitted.
So it is by no means certain that having an in-depth specification would have prevented this from happening. The only thing it is likely to do is make the contractual situation unequivocal.
That’s not the real question though, what we have to consider is what the result of us batting it back to the customer with the comment “well we never said it would do that in the first place” would be. Even with a water-tight contract such a response would have to be carefully considered.
The software industry today relies on good customer relations, repeat business and reputation. We want the customers that are using our software to continue using our software, not least because they pay an annual licence fee. Even if you’re an app developer for smartphones you have to be careful – if you annoy your customers they post bad reviews and there’s only so many bad reviews you can face down before you app dies in favour of someone else’s that has better reviews.
From a purist software development point of view this list ordering is a feature request, indeed that’s what we’ll call it internally. The relationship with the customer however is a far more complex matter – every customer tries to get at least some of their feature requests through as bugs in the hope that they’ll either get them for free or that they’ll be treated with a higher priority. If you let the customer walk all over you then you’ll be in trouble. On the other hand the age of profiteering has long passed and if the customer thinks your trying to charge them unjustly to fix genuine bugs then you could find your reputation damaged and your business will suffer as a result.
We may think of Computer Science as a logical, scientific profession but the reality of being a good software developer is that you not only need to understand logic, but you need a good grasp of politics too.
There’s almost a throw-away comment in my last article, The Internet and the Office Roof, “I was prepared”. We all knew about the St Jude storm and we knew fairly well when it was going to hit. But what does “prepared” mean? What did I do and what do I have that made me well prepared?
In many ways that story is far more important than me jumping on and off the office roof trying to find some mobile Internet. There’s some kit I have that’s useful but let’s start here because it’s simpler;
Things I Did Before the Storm
Loose objects outside are problematic. They can get blown around and damage themselves, other things or simply get blown away. So the day before the storm I had a wander around. Bins are a classic problem but ours have a little pen they live in and I thought them safe.
Garden furniture is another problem but ours is folding, so I collapsed it all and weighted it down. It’s quite heavy so in that state I was confident it wouldn’t budge.
I also surveyed the structures around the house – the decking, the fencing, the bin pen, the Wendy house. Were these in good condition? Were there any parts loose or vulnerable that might need fixing down?
Water Container
I took the time to draw some water into the camping container. Some large scale power outages were possible and there are a lot of electric pumps in the water network. Although we didn’t lose water there were disruptions nearby.
Rechargeable devices are great, but useless if they’re not charged. So the day before the storm I made sure that everything that I use and all out battery packs were on charge well in time for the storm.
I had a good look at the house too – did everything look in good order? Again anything loose or vulnerable could cause big problems. Chimney pots for instance are pretty big and heavy, you don’t want a loose one crashing through your roof.
Things I Have that Might Help
An “A” rated freezer like mine is a far better place to store cold food – even if it’s turned off – than a cool box. However the greater the thermal mass in the freezer the longer it will remain frozen. If you have a load of cool blocks it’s worth chucking them in the freezer a day or two before the storm (which I did).
I always keep a stock of tinned and packet food in as well because this is the country and things happen. A few days worth of relatively nonperishable food is a good thing to have regardless. I make sure that I always have rice, lentils, dried egg noodles, soy sauce and spices. You can make a stir-fry with all sorts of things, most notable vegetables which you can store for a good period of time without a fridge and you can always make lentil curry.
I have a lot of camping gear – stove, lights etc. I made sure they were all easily accessible. It’s nice to have a kettle rather than just boil water in a saucepan, but it’s by no means essential!
Batteries
A lot of camping things are battery powered rather than rechargeable so I make sure that I always have a small stock of (the right) batteries.
Three of my favourite (portable) lights are these.
Nightsearcher Trio
The NightSearcher Trio is available from a number of places. It’s a rechargeable LED torch and it’s exceedingly bright. It has a big handle that’s easy to grab and a flat bottom which means that it can be placed upright – pointed at the ceiling. In that mode it will happily light an average sized room. It claims to work for up to 23 hours. I can’t vouch for that but I can vouch for the fact it lasts many hours indeed.
UltraFire Torch
The Ultrafire Q5 is another torch, but it’s a pencil variety. It can run off its own special battery (expensive) or a pair of AAs. It’s nothing like as bright as the Nightsearcher but is pretty impressive for the size.
Tilley Lamp
A Tilley Lamp – this is a pressurised paraffin lamp so you really need to know what you’re doing to use (and maintain) one of these safely. It throws off a reasonable light and will last several hours on a tank of paraffin (kerosene). Its big advantage is that it also throws off a lot of heat as well so if you’re stuck with neither light nor heat it’s ideal.
The most dangerous thing about these is getting one lit. After that – with reasonable caution – they’re safe to use indoors.
Powergen
The Powergen is a mobile phone power pack. It’s essentially just a battery with 3 USB ports on it that provide power. It also has a LED torch on it. It’s good for about 4 charges of a modern smartphone.
Old Corded Phone
A corded telephone – when the electricity fails generally a cordless phone base station stops working. The resilience of the UK Telephone network is actually quite good and the chances are that even if the power is out the phone will actually still work – as long as you have a phone that doesn’t need any power other than from the phone line itself. This particular phone lived in a workshop for years, hence the sawdust.
Nokia 6310i
A Nokia 6310i. It’s an old, stupid mobile phone but from a disaster-coping view it stands out in 2 ways.
The transmitter and receiver on this model were particularly good.
It has a genuine 3 week standby time.
This gives me a pretty good chance of being able to communicate even if everything else goes wrong – and for some time too. Although I still have to sit on the office roof (or walk up the nearby hill) to use it.
Tea Light
Tea Lights – small self-contained candles that apparently can last up to 8 hours. They last 4, but they’re cheap and can be used relatively safely without the need for candle-sticks.
12V Power Pack
A 12V power pack. These are actually designed to start cars that have a flat battery but they come with a range of accessories, notably torches and car accessory sockets. We have one primarily to keep our smart-phones topped up for a week or so when we’re camping well away from power. There are a lot of things you can run from a car accessory socket. Some power packs even have inverters so you can use normal household appliances with them (although probably not for long).
Pure One Portable Radio
A battery powered radio – in this case actually a DAB and FM / AM radio. Local radio is often the most reliable source of information when all other forms of communication are failing.
Bombay Sapphire
Gin – it’s good for cleaning wounds and in dire circumstances it can be used as fuel. Apparently some people drink it, too.
Work Related Things
Half of your county might be without power but the rest of the world doesn’t stop. You’ve got to try to continue to work as best you can. Naturally I have back-up plans.
My main machine is a high-end laptop with an SSD that I normally use docked. This has two advantages.
It’s effectively its own UPS.
I’m mobile. I can work anywhere I can put the laptop down without having to move a lot of stuff.
I have a good quality laptop backpack bag. This means I can cycle easily with my laptop – useful if for whatever reason the car in unavailable or, let’s say, the local roads are strewn with broken branches, fallen trees and other debris.
I did consider getting a mobile broadband deal but I end up without Internet / WiFi so infrequently that it just makes no sense. For the amount that I need it I can tether my phone instead.
My parents-in-law are in easy cycling distance and they’re on a different telephone exchange and use a different ISP which means that the chances of the Internet failing in both locations is fairly small. There are also (actually) a few WiFi hotspots in the local town and there’s another town that’s not too far away that has loads.
I have a SIP phone which means that I have a telephone – the same telephone – wherever I can find some Internet with half reasonable bandwidth.
I thought I’d got away without any ill effects from the “St Jude” storm on Monday – not so. My Internet failed yesterday morning; I felt like I’d had an arm cut off.
I’m a remote worker – have been for 2 years (a fact that I really should blog more about). I knew the lack of Internet was going to cause problems but I didn’t realise exactly how much.
Some Internet, at least!
The first thing I had to do was call the ISP to find out what was up. What’s their phone number? Well it used to be on a piece of paper under the router along with all the technical (but not security) details of the connection. The paper was missing. There’s no mobile phone signal at my address so the next image I would like to present to you is me, stood on the roof of the office at the end of the garden waving my phone in the air because if you’re really lucky on a clear day you can get some mobile signal there. Eventually I got enough mobile Internet packets to find their phone number.
Apparently the Internet problem is due to local power problems and they can’t give me a fix time because the power company won’t give them one.
No problem I say to myself – my team know what they’re doing they can survive without me as long as it’s not days. I’ll just let them know. Precisely how am I going to do this then? I’m usually pretty easy to contact, Email, Skype, MS Lync, Google Talk, SIP phone, none of which are going to work. I don’t even have any of the team’s mobile numbers. Telephone again then. The next problem is that I never actually call the Departmental Office so I don’t know the number.
That’s me on the roof of my office again waving a mobile phone around for 10 minutes trying to find the number before I realise that although Outlook won’t connect I will still have my email and the office number will be in someone’s signature – sorted.
Now down to business and for the first time I’m ahead of the game. I know I won’t be able to connect to the Team Foundation Server so I take a back-up of the source tree and then open the solution offline. The problem I’m working on is a complex one, the code didn’t make much sense – I mean I understood what it did, but what it did didn’t seem logical. I needed some context so I wondered if it had always been done like this. Usually I’d look at the module history, but that’s all in the Team Foundation Server that I don’t currently have access to.
Never mind I think, I’ll tackle a different problem, one that’s SQL Server based. Quickly I realise that I can’t remember the syntax for the OVER / PARTITION aggregate functionality. So I have a go, get it wrong and then hit F1 for some help. Which is online, so that’s a non-starter.
But I do have a book on SQL Server that I can refer to. In Safari, the online book system. That’s not going to work either.
Clearly this lack of Internet is becoming quite a problem. I am inventive though and I’ve got a spare satellite TV dish. I wonder to myself if perhaps I mount my mobile phone at the focal point of the dish and direct it at the most line-of-sight phone mast I might just get enough signal strength to tether the phone. I suspect that the answer is a strong no but maybe there is something sensible and practical I can do to improve the signal. I’ll just Google… oh wait, no I won’t.
Small scale disaster planning though is something I blogged about a while ago so I should be on top of this right? The primary backup plan for power / internet loss is to go to my in-law’s house in the nearby town. The problem is that they’re at work. My wife has a key but she’s away on business. To be honest this kind of suits me because I find laptop screens rather limiting, I far prefer the large pair of monitors I have in my office so if I can manage without Internet that’s better for me.
Nevertheless it would be good for me to get some Internet at some point, check emails, make sure the team are OK etc. The secondary backup plan is to find some public WiFi. There’s none in the village (and it wouldn’t work even if there was) so I ponder popping into the local town for lunch – the car is also away with my wife on business but the weather looks OK and I have a bicycle and a laptop backpack bag. I wonder what the weather forecast will be for later though – I’ll just look that up on the Internet… erm, no. Oh well, I can risk it, I have wet weather gear. I’m certainly not going to risk it though unless I can guarantee a cafe or coffee shop that has WiFi and I don’t remember seeing any adverts when I was last there. I’ll just Google… oh no, wait, no I won’t.
Just as I’m thinking this something pops into the back of my mind – I’m sure I remember reading when I signed up for my broadband Internet access that they had a backup dial-in option. The details of that will also be on that missing piece of paper but I remember printing it out from an email. So it’s back onto the office roof for me searching through my email history to find the details. They do indeed, but sadly it’s a national call rate number which means it would get expensive very quickly – but it was enough just to check my email.
At about 9:30pm the situation got even worse, I lost electricity as well. I live in the country where there is no street lighting. I was on the stairs and it suddenly went dark. I was prepared for this – there were torches at strategic points around the house and I got the candles and lighter out so I could find them in the dark.
What I wasn’t quite prepared for was how dark it was, it was pitch black. So I sat down with a view to waiting until my eyes picked up some light. Unusually for the house however I had my mobile phone in my pocket so a few seconds later I was carefully making my way down the stairs to one of the torches.
Electricity is another strange thing – it’s easy to overlook how important it has become to our lives.
The freezer was defrosting. As I had no idea how long I’d be without power the only thing I could do was put some towels under it and hope it wasn’t too long.
The central heating is gas, but of course the pump and all the controls are electric. Fortunately I have a multi-fuel stove which is definitely not electric in any way at all and being honest it wasn’t that cold.
Fortunately the cooker is dual-fuel, which means that the gas rings still work. It does leave me without a grill or oven though which limits what I can cook.
The house phone is a cordless model – the handset might work but the base station won’t. I keep an old fashioned corded handset just for this, so I was able to plug that in. It is worth noting that you shouldn’t assume that if you’ve got no power the phone won’t work. In reality it usually does – in the UK at least.
My alarm clock is a Lumie Bodyclock – it’s great most of the time but it is very definitely mains powered. I don’t have a mechanical alarm clock, but I do have a mobile phone so there was a solution there.
The weirdest thing though was this – it was night and I didn’t know which of the house lights were turned on and which off. This meant that if the power came back on at say 3am (which it did) some of the house lights would turn on, possibly without me knowing.
This morning I had power but still no Internet, so I’m currently sat at my in-law’s dining room table borrowing their Internet and just having to deal with the tiny laptop screen and horrid keyboard.
Being well prepared was definitely worth it – clearly I knew that losing electricity would be a serious inconvenience but just how much I rely on the Internet surprised me considerably.
The other day I saw someone do something very much like this and it made me cringe a little. There’s no problem with this when the number of items that are being dealt with is small, but as the number of items increases performance will take a spectacular nosedive.
static string[] composers = {"Pyotr Ilyich Tchaikovsky",
"Gabriel Fauré",
"Sergei Sergeyevich Prokofiev",
"Jean Sibelius",
"Ludwig van Beethoven",
"Benjamin Britten",
"Erik Satie"};
static void Main(string[] args)
{
Console.WriteLine(" L I S T I N G S H O R T N A M E D C O M P O S E R S");
Console.WriteLine(" =========================================================");
IEnumerable<string> shortComposers = composers.Where(x => x.Length < 15);
for (int i = 0; i < shortComposers.Count(); i++)
{
Console.WriteLine("Composer {0} => {1}", i, shortComposers.ElementAt(i));
}
Console.Write(" - PRESS ANY KEY TO EXIT - ");
Console.ReadKey();
}
What’s the problem? Well in this trivial example nothing at all, but if the list of names were a bit longer then we could find that this code runs very slowly indeed. There are two problems.
C#’s for loop combined with IEnumerable’s .Count() method is somewhat toxic.
In order to understand why we need to look at what .NET is doing behind the scenes. Originally I used the rather excellent IL Spy to decompile part of the .NET Framework itself.
Since then Microsoft have actually published the source – so let’s take a look at what .Count() really does.
public static int Count<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw Error.ArgumentNull("source");
ICollection<TSource> collectionoft = source as ICollection<TSource>;
if (collectionoft != null)
return collectionoft.Count;
ICollection collection = source as ICollection;
if (collection != null)
return collection.Count;
int count = 0;
using (IEnumerator<TSource> e = source.GetEnumerator())
{
checked
{
while (e.MoveNext()) count++;
}
}
return count;
}
So if it’s a ICollection<T> or a plain ICollection it returns the Count property of the object, if not it gets the enumerator and counts up every item in the IEnumerable.
Now we have to look at C#’s for loop and how it’s evaluated. If we look at the C# 4.0 language specification it says;
A for statement is executed as follows:
If a for-initializer is present, the variable initializers or statement expressions are executed in the order they are written. This step is only performed once.
If a for-condition is present, it is evaluated.
If the for-condition is not present or if the evaluation yields true, control is transferred to the embedded statement. When and if control reaches the end point of the embedded statement (possibly from execution of a continue statement), the expressions of the for-iterator, if any, are evaluated in sequence, and then another iteration is performed, starting with evaluation of the for-condition in the step above.
If the for-condition is present and the evaluation yields false, control is transferred to the end point of the for statement.
Or in other words every time the loop goes round the Count() method is called. So if there are 1000 items in the list then the Count() method will be called 1000 times. Each time the Count() method itself is called it will get the enumerator and count up 1000. So that’s more than 1,000,000 operations that are performed when only 1000 should have been.
It’s easy to fix…
int shortComposersCount=shortComposers.Count();
for (int i = 0; i < shortComposersCount; i++)
{
Console.WriteLine("Composer {0} => {1}", i, shortComposers.ElementAt(i));
}
Now there are 2000ish operations performed because the Count() method is only called once. Note that there is some overhead in creating the shortComposersCount variable, so for small numbers you may find that it’s faster just to leave the Count() where it was. If you do leave it as was though be aware that performance will degrade exponentially as the count increases.
.ElementAt() is inefficient
To look at the second problem let’s fire up the Dot Net Reference Source again and take a look at what .ElementAt() does.
public static TSource ElementAt<TSource>(this IEnumerable<TSource> source, int index)
{
if (source == null)
throw Error.ArgumentNull("source");
IList<TSource> list = source as IList<TSource>;
if (list != null)
return list[index];
if (index < 0)
throw Error.ArgumentOutOfRange("index");
using (IEnumerator<TSource> e = source.GetEnumerator())
{
while (true)
{
if (!e.MoveNext())
throw Error.ArgumentOutOfRange("index");
if (index == 0)
return e.Current;
index--;
}
}
}
Having seen what Count() does that won’t surprise you. If the IEnumerable doesn’t implement IList then ElementAt() gets the enumerator and calls MoveNext() the requisite number of times to move through to the specified position, then returns the current item. This is not good – we’re performing a whole heap of unnecessary operations and the performance drop off as the number of items increases will be horrid.
So we need a bit of a rethink – in this case simply using a foreach instead of a for fixes everything neatly.
int i=0;
foreach (string shortComposer in shortComposers)
{
Console.WriteLine("Composer {0} => {1}", i++, shortComposer);
}
This way the enumerator is only got and enumerated once – the performance improvement of this way of doing it over the original for loop implementation will be an eyebrow-raiser.
Comparing this with an array
But what if we have to use a for loop (for some other reason)?
I won’t go into the details of the implementation of the C# array but…
It has a Length property (not a method) that directly returns the size of the array, it doesn’t do any counting.
It (obviously) has an indexer property that directly returns an item from an array – again no counting involved.
So an array also solves both of our problems…
string[] shortComposers = composers.Where(x => x.Length < 15).ToArray();
for (int i = 0; i < shortComposers.Length; i++)
{
Console.WriteLine("Composer {0} => {1}", i, shortComposers[i]);
}
This isn’t bad, but you must be aware that the instantiation of a new object – the array – introduces quite a bit of overhead. You may find that using this construct is slower than the original in some surprising circumstances. For instance if the item is a value type (such as a struct or string) then the overhead of creating an array of them can easily be more than the cost of doing all those extra operations. Reference types (e.g. objects) will be less prone to this.
It’s not safe!Conclusion
Be aware that a lot of LINQ operations end up iterating through item by item performing some operation or other. This fact can be hidden in innocuous looking method calls such as ElementAt(). The number of unnecessary operations can very quickly get out of hand, especially when combined with other iterative operations.
If in doubt, use the source. If you haven’t got the source for whatever you’re using then, if it’s legal to do so where you live, crank up your favourite .NET decompiler and find out what’s going on underneath.
It’s week one again in the university calendar which seems like a good time to welcome our new students, our new interns at Seed and in fact everyone who’s starting university this week.
There are plenty of articles on university life etc. so I’m not going to repeat what they say. What I want to talk about is that feeling when you start a new job or even a new could that you have no idea what you’re doing and that you’re floundering. It’s entirely normal, I think it’s something that most people go through. When you start a new job the amount you have to learn is pretty substantial. You might be able to code well enough in C# but when someone hands you a 200,000 line project it’s going to take you some time to get your head around it, and I don’t mean a few hours. For a project that size it will take months before you’re fully up to speed with the code base.
Also, although you may know systems like TFS they way the new firm use it will probably be different. Even silly things like the fact that you won’t know their internal procedures very well so admin tasks will take longer meaning that you have less time available for development.
Many of the people around you might seem like they’re wizards in comparison to you but the reality is that they’re just further down the road with the code, the methodologies, the systems, the business and even things like they might have known the original developer so they might understand why some things are done they way they are.
This is especially true if you’re a new graduate or intern – the realities of software development are very different to the academic environment and it’s going to take you a while to adjust and to get up to speed with everything that’s going on. This is normal, don’t worry about it and do ask for help and advice when you feel unsure.
Be aware also of “impostor syndrome“. It’s pretty common in the world of art, music and comedy where artists are often confused by their success, not believing that they’re actually very good or deserve the attention they’re getting. From the people I talk to it seems fairly common in the computer science world too. If you’re feeling that you’ve somehow lucked your way into a position that you don’t really deserve or that you’re surviving not by a talent for developing software but by conning people into thinking that you’re doing a good job then this might be something that you need to be aware of.
Reading Time: < 1minuteCoprinopsis Atramentaria, I think
This morning I was greeted by these little beauties in the garden. I’m mildly familiar with the destroying angel and the death cap as Britiain’s only truly deadly mushrooms. Initially I thought they might be the former but on closer inspection (or rather getting the book out) I think they’re common ink caps, which it transpires are nearly as bad.
Apparently the ink cap is quite edible, unless you consume any alcohol. If you do then the reaction produces a very nasty poison that has resulted in death. This can happen anything up to three days after consuming the mushroom.
I won’t be putting these in my soup for lunch then, especially as I’ve got a table booked in the The Dog for this evening!
It’s a problem we as developers face time and time again, it works on my box but for some reason it doesn’t work on the customer’s machine and it’s not reporting anything useful in the error stream.
Maybe we could install Visual Studio on the customer’s machine and run it in debug? Maybe, probably not. Even if the customer lets you it probably involves punting significant chunks of binary around the place, a lengthy install and although Microsoft probably won’t mind as long as you uninstall it when you’re done it probably does violate your Visual Studio licence.
A much lighter alternative is to use the .NET Command Line Debugger. It’s available as part of the Windows SDK which is significantly less hassle to install than VS and far less likely to get you into trouble with the customer or with Microsoft.
The debugger is MDBG.exe and is likely to be in C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin (which you might consider adding to the PATH).
—=== Edit 2013-08-30 ===—
In fact a little research indicates that you can be even more lightweight by installing the relevant parts of the Windows SDK on another box and then just copying Mdbg.exe and MdbgCore.dll to a temporary directory on the target machine.
—=== End of Edit ===—
—=== Edit 2014-11-21 ===—
In an update that could easily be decorated with the attribute [FFS] it appears that mdbg.exe is no longer part of the Windows SDK. Instead it can be found as a “sample debug program”—=== End of Edit ===—
You can load the executable you need on the command line, e.g. C:\Program Files\MyCompany\MyProduct>mdbg MyProduct.exe
MDBG Finds the Problem
Ah, that’ll be it. I’ve made a typo in one of the XML config files. That’ll be a new item for the backlog then, “Make the app write some useful information to the error stream when some numpty screws up the XML“. It’s fine that it terminates, just not that it gives no reason for terminating.
Back on topic, MDBG.exe itself is easy enough to use, it’s even good enough to list its basic usage in response to a ?
To waterproof or not to waterproof, that is the question. Will I get wetter from the inside than the rain could ever make me and what’s the problem with getting wet anyway? Last time I checked I was waterproof.
Usually in the UK getting wet is a problem only because you get cold but on warm still days like this that won’t happen. Putting your phone and wallet in a waterproof pouch and just getting soaked is a serious option.
Today I went for the waterproof jacket only which proved the right decision, the heavens opened when I was in the middle of nowhere and trying to dry out on the 09:43 to London could have been awkward.
PS – I then decided that as it was London I wouldn’t need the waterproof as I could always nip into somewhere under cover, got caught in an open space and got completely soaked.
Reading Time: 5minutesGeo-Tagged: Dove St Inn Beer Festival
I don’t like giving air-time to scare stories – indeed I seem to spend rather a lot of my time debunking them. I find a lot of them distasteful in attempting to use the most extreme means they can to frighten people. This American “NBC Action News” report (video) definitely falls into that category. I think I need to explain this – sensibly – without trying to frighten anyone.
The story, for those who choose not to watch, is that if you post images from your smartphone to online images services (such as flickr) you could be giving away a hell of a lot of personal information that you had no intention of making public. That information could be very useful to criminals.
Now between the ridiculous hyperbole, the desperate attempts of the newscasters to instil panic into every parent and an American “expert” who is clearly no expert at all there is actually some degree of truth behind this. Not only that but it somewhat falls into my area of expertise.
What we’re talking about is geo-tagging and it’s not new(s) – it’s been going on for years. Pretty much all smart phones and a good number of digital cameras have an option to record where and when the photo was taken (generally using GPS, the same system that sat-navs use to work out where you are). Those phones and cameras then write that information into the image itself in what’s called a geo-tag. If you post that image to an online image service then, depending on which one you use and various options etc. that information might stay in the file and it’s possible that someone viewing the file might be able to retrieve that information.
To do so – to find this information out – is in no way hacking. You don’t need to get access to any accounts or run any strange programs downloaded from dodgy darknets. Beneath is a screenshot of a free tool that came with my camera and all I’ve done is to use it on the image at the top of this page (which I’m very deliberately posting publicly).
You could use this tool on any image that contains a geo-tag to find out when and where it was taken. This one is a few metres out – basically the wrong side of the street. That’s fairly typical. I did some experiments around my house last night however and it was possible for me to identify which room I was in when the photo was taken.
Now if it had been one of those images that I’d taken last night that I’d used in this article, rather than giving away the location of The Dove St Inn I would have given away my home address.
The amount of information you could give away like this can build up. If you post an image for which the content is clearly identifiable, or there are comments that clearly identify the place or activity then someone could quite easily build up a picture of your life. Your home address, your childrens’ schools, what parks they play in and when, when you’re away from your house, your elderly relatives houses and when you typically visit them, when you’re on holiday, etc. etc.
They could, but actually the chances that anyone is actively stalking you are pretty slim. There are billions of people out there after all. Also remember that there are quite a few ducks that have to line up for this information to be revealed and if even one of them is out of line then you won’t be publishing this information to the entire planet.
Another aspect of this is story is the fact that if the geo-tag information is in the image and that image is publicly available it can be indexed for searching. So it’s possible to search for images by their location – instead of searching for just images of kittens you could search for images of kittens within, say, 500m of a particular location. If you got any results the chances are that you’d know pretty much the house that they were at. I do find that a little concerning.
Over lunch I thought I’d give it a go – I wondered who else had posted public pictures of – or from – The Dove St Inn. So I searched flickr for “Dove” within a small area of Ipswich.
Dove St Pictures
All perfectly innocent in this case but it proves the point – you can search for a term and find images connected with that term in a given area.
So what can we do to prevent this from happening? Essentially the message is simple, don’t post geo-tagged images to public sites unless you’re really happy about what it reveals. Your options are as follows.
Turn off geo-tagging on your phone and cameras. My smartphone has an easy option in the camera app itself called “store location”. If you turn it off, the location is never stored in the image and it can never be made public.
It is kind of handy to know when and where an image was taken though – thankfully there are other options.
Make sure that you never post anything publicly. Many social networking sites and image hosting sites have privacy controls that allow you to ensure that only people you trust can see the photos.
Remove the geo-tags before posting. The Nikon ViewNX utility that came free with my camera can remove geo-tags as well as view them. I bet there are smartphone apps for it too.
Use an image service that has the ability to remove geo-tags of images that you’ve posted – flickr for instance has this option (under “defaults for new uploads”) and I imagine most of them do.
If you don’t find “geo-tag” or “location data” in your privacy settings then look out for the term “EXIF” – this is the format that most smartphones and cameras use to add information such as the camera brand and exposure details as well as the location to the image file.
Personally I prefer option 2 – I tend to restrict who can view my images. I only make a few publicly available and I pay close attention to what those ones reveal, not just through geo-tags but also through the content of the image itself.
So in conclusion your smartphone is not a hot-line to the Cosa Nostra and it’s really rather unlikely that anyone with any criminal intentions is paying any attention to any images you’re posting online.
It is however worth checking if you’re posting geo-tagged images with no privacy control and if you are then have a think about whether or not you’re happy with that. If not then delete them, remove the geo-tags or make them private and then implement some sort of strategy to make sure you stop doing it.
