How to DEBUG C++ in VISUAL STUDIO

absolutely love these pillars hey also guys my name is Luciano and welcome back to myself life series so today we're back on the couch you guys seem to dig that didn't have much time to go anywhere exciting for this video however the content is going to make up for that because today we're going to be learning all about how to use Visual Studio to debug our code now in planning this series unfortunately I have the difficult decision I was trying to decide which video goes where in what order and all that stuff a lot of these videos kind of depend on each other so if you see me mention things in certain videos that I haven't mentioned in previous videos it doesn't mean that I've kind of glossed over the topic it just means that it's probably going to come later that being said though debugging is just such an important part of programming and not just programming but of learning because if you know how to debug your code you're actually going to understand how the program works and how the computer actually runs your code so I thought I'd cover debugging pretty early on in this series because I'm actually going to use a lot of what we cover today to explain how the rest is language and how computer programs work in general in this video specifically like all of my support videos I'm going to be using Visual Studio however this concept applies to pretty much any IDE out there most ideas will support exactly what I'm going to show here today just might be in a different place but basically we're going to be covering two important features for free is a three I don't even know how Matt we can probably break this thing is to find breakpoints see that joke earlier was funny because breakpoints is a big part of debugging and looking at memory the breakpoints and reading memory those are kind of the two big parts of debugging it and of course you will be using them together so in other words you'll set breakpoints in order to read memory so what's the point of debugging what do I mean when I say let's debug our code the word debug means to debug right so to remove bugs from our code in order to remove a bug from our code we have to diagnose what with our program and that part can actually be pretty tricky even if you're well experienced in the language at the end of the day you have to remember that the computer is always right and by always I mean like 99% of the time it's very unlikely that you did something correctly and then the computer just didn't work as expected it's usually it's usually you who made a mistake and coming to realize that it's something that is very important for programmers you will soon learn that the computer is pretty much always right so really this is all about figuring out your mistake what did I do wrong what did I do to deserve this so breakpoints reading memory let's take a look so here I have a pretty simple visual studio project I've got my main file here which calls logs is the log CBP and logs are age that we made in the previous video in the video about C++ header files what we're going to do first of all is we're going to set a breakpoint and then we're going to step through the execution of our program so what our break point so a breakpoint is a point in our program at which the debugger will break and the word break here just means pause so what will happen is we can basically set a breakpoint on any line of code in our program and when when the execution hits that line it will pause it will suspend that execution thread on our case the entire program and let us take a look at the state of this program and by state I'm really referring to memory we can pause our program and just take a look at what is going on in its memory remember the memory of a running program is pretty much all it's got it's what every variable is set to it's what function will be called max everything when you will you break it down memory is all older there is really so being able to view memory is incredibly useful in diagnosing what the issue is with your program because by viewing the memory you can see what every variable is set to and be like hey this variable shouldn't be set to this value something's obviously wrong you can also step through the execution of your program line by line so I can put a breakpoint on line five and then just just hit a button and the program will advance just one line of code further into line six you can also step into functions to see where they'll take you it's just just so much you can do with breakpoints it's amazing and it's incredibly useful and if you're programming without this then I don't even know what you're doing so back to Moodle studio in order to set a breakpoint individual to you you can either just hit f9 and it will set a breakpoint on that car line of code or you can click on this sidebar anywhere under side by here just click once and you'll set a breakpoint obviously if you do something like set a breakpoint on line 3 that's not really going to work because there's nothing on line 3 is ever going to get executed so make sure you set a breakpoint on cones that actually will be executed on lines that will actually be hit so line 6 of course will be here because that's the first line of code in our program and then all you have to do is run your code through the debugger one tip is to make sure that you're in debug mode because if you're in release mode the compiler will actually change the way that your code look and your breakpoints might not ever get hit because your program has been rearranged we'll talk more in depth about what release mode actually does and all that stuff later but the gist is if your debugging just make sure you're in debug mode if we then hit the local windows debugger which ensures that we're actually running with the debugger attached our program will run and you can see that the focus from our program is actually stolen back to visual studio and we change into this kind of different alternate layout along with a big yellow arrow on that breakpoint indicating that that is currently where the instruction pointer is at in our program the main areas to look at here are basically this continue button which will continue executing our program like normal and then we have a bunch of buttons over here to let us step in to step over or step out now these three buttons are going to control exactly what happens next in our program so step into is going to step into the current function that is on this line of code if there is a function so in this case if I have stepped into an to log we would actually step into the log function so that we could see what it does step over is going to step over to the next line of code in this current function and step out is actually going to step out of this current function and take us back to whatever call of this function which in this case is if this is the main function will be the C standard library you can also use f11 to step into f10 step over or shift at 11 to step out so let's step into this log function and see what happens I'm going to hit eleven okay check this out so we step into this function we're at the very beginning of the SAP frame we haven't actually begun executing any code here we're just setting up this function stack frame we can hover our mouse over this message variable and check us out it tells us that it's set to hello world so that's the second part of debugging right we're reading memory now how cool is this if I hit f10 is going to bring us up to this line of code now the fact that the yellow arrow is on this line of code means that it actually hasn't executed this line of code yet it's just it's on there it's about true as soon as we hit a button like a scan or shift f11 to get out of the function or f5 which will continue our program as soon as we hit one of those is going to execute that line of code and possibly more but the yellow arrow means that it is on that line of code it hasn't actually executed that line of code yet so if I bring up my program right now you can see that that hello world message has not been printed but check this out if I hit at can and then check back look at that we've printed hello world because we've called that STD see our function and it actually has printed that text to the console we've executed that function so by setting breakpoints and by stepping through our program we can literally run our entire program line by line which of course is really cool and really useful when you're trying to figure out what you've done wrong anyway back here if we keep hitting f10 you'll see that we'll eventually get back to our main function f10 again we'll bring up to the next line of code in our main function and this will kind of keep going if I hit f5 is going to continue running our program as usual and I can just get an to it to propose my program as if it was just running normal alright it's a pretty cool stuff and even though this might look really simple this is actually really all there is to it I mean I've shown you guys pretty much everything I'll show you some more example so that you really get it but that's kind of the gist of it so let's go ahead and make some more variable to make things interesting I'm going to make an integer called a set it equal to 8 I'm going to do a plus plus which will increment a by 1 so in other words it will set a to be 9 I'm going to create a c string here by just typing in college our string equals hello i'm going to write a very basic for loop here that's going to iterate through the string and print each character out on a separate and then I'll leave in my log hello world for good measure so if I run my program with our breakpoints at all just to see what even happens you'll see that we get basically something like this where we have hello and then hello world all right now I step through this line by line and when I set a breakpoint at the very top here on a and just hit f5 all right cool let's take a look what a is what why is it negative 858 million well remember that yellow arrow doesn't mean that we've actually run this code we're actually just about to run it but we haven't actually executed line six the one that actually creates and sets that a variable so what the debugger is currently showing us is what the memory where a would be is showing right now and since we haven't actually set that variable to anything yet it's just uninitialized memory which means that this value is just showing up whatever that memory actually contains this would be a fantastic time to bring up these three important windows that we have here Otto's locals and wash orders and locals will basically just try and show you local variables or variables that it thinks might be important to you watch on the other hand lets us actually monitor variables so what I can do is I can type in a which is the name of the variable and here enter and you can see that it's showing in the value of a if I also want to view what string is I can also put that in and it's going to show me what string is now of course we have an initialize this memory yet so it's currently as completely useless it's just garbage but as we step through our program these values will update to show what's actually in the memory speaking of memory there's actually a view that we can use to view the entire memory of our program now of course it's called a memory of you so if we don't debug windows memory and memory one we're going to be greeted by this weird-lookin panel here that's going to show all of the memory of our program so on the very left we see the memory addresses in the middle we see the actual data the actual values represented in hexadecimal format and on the right we see the ascii interpretation of those numbers if you want to locate where does a variable actually installed as a memory of your program you need to know its memory address and to do that we can simply type in ampersand and a so the ampersand in front of the variable name will actually get that bear murmuring address if we hit enter we're going to be taken to the memory address of that a variable which in this case is a whole bunch of C's so that number that safety number is actually a hexadecimal value if you want to see what that is in decimal you can bring up a calculator if we switch to the programmer view we can type in two hexadecimal value if I just click on hexadecimal here type in cc as you can see what that value is in decimals 204 so 204 CC why is it set to that isn't that memory just supposed to be random a whole bunch of safeties seems kind of specific now that's the cool thing about debug mode and also why debug mode slowed down our program it's because the compiler will actually make our program do certain things certain extra things it's going to make allies easier when it comes to be bugging so for example the fact that this memory is a whole bunch of cc's means that it is uninitialized staff memory so what actually happened is the compiler knows that we're making we're trying to make a variable but we haven't initialized it yet so what I'm going to do is actually fill that memory with CC so that if we're debugging our code and something goes wrong we can look at the memory we can see that it's set to CC and we can be like oh of course I never initialized that variable that's why this is going all wrong now by doing extra things like that like setting our memory to CC before we initialize it obviously our program is doing extra things that are going to slow it down so we don't want to be doing that in release mode when we actually release our program when we ship our game we want to be doing all that but when it comes to debugging is very useful so if I come over here and I hit ask and a lot of things are going to happen one other thing you can do actually in this watch window is right click and select hexadecimal display and so now you can see that the value of a actually is a whole bunch of C's which of course means that a is currently on an initialized stack memory let's go back to our non-tax decimal display and let's hit f10 and a number of cool things are going to happen so namely in this watch window our value has changed to a it's also red which indicates that it's changed since the last breakpoint our instruction pointer has moved down which is showing that it's now about about tax if you're defining code hasn't done it yet no no not yet but it's about two and then if we look in our memory view you can also see that these four bytes of memory has been set to eight by the way I should probably mention that every two digits here is equal to one byte that's also why web viewing is in hexadecimal because if we do that every two hexadecimal digits are always going to align to be one byte of memory so we can tell just by looking at this that these eight hexadecimal digits are four bytes of memory and you can see that it's been set to eight so that's what we're doing that's all we're doing right now we've paused our program and we're taking a look at its state we're reading its memory if I hit f10 again we're going to advance this is now set to nine it's such nine here as well pretty cool stuff you can see that string is still uninitialized stack memory but check this out I'm about to initialize in honor so if I hit f10 it's initialized because this is an actual pointer it's also telling us the memory address of that string so if I was to copy this memory address here from the what window and paste it into my memory view and hit enter look at this I'm taking to these bytes which in this ask interpretation you can see that it says hello and what's really interesting is that if you actually keep reading you can see that our program literally contains memory close to this hello variable that says stack around a variable was corrupted the variable is being used without being initialized obviously our program containing strings like stack around the variable was corrupted in its memory is not something that will exist in release mode but it's just another great example of what will actually happen in debug mode to help you debug the program okay cool so things getting real interesting here because we've run into this for loop what's going to happen if I keep advancing through this now we haven't covered for loops or any kind of control flow statements in this series yet the next few videos are probably going to deal with it I really wanted to cover the debugger first so that we can actually step through this control flow statements in the future and see how they work and you guys already know how to use this debugger view but basically of all it's going to do stuff multiple times so if we step through this program you can see that is set to zero it's going to grab index 0 from this string which is going to be the very first character in the string which is a capital H if we hit f10 we can hover our mouse over C and see there's a set to H we can also come over here into watch and just type in C and you can see when our taking a look at what C is when I hit f10 is going to log that letter to the console and then when it gets back to this curly bracket it's going to run this comparison it's going to compare is I less than 5 and then if so it's going to increment I and then jump back into here so if I hit f10 you can see we jump up here to do the comparison if I hit f10 again we've done the I plus plus I is now 1 we're going to do the same thing all over again except this time I is 1 so it's going to grab the second character which is the letter E and continue on in this case C is equal to e you consider this change here you know watch if we come up here do ampersand C and hit enter you can see we have 65 which is the letter e according to our asked of you fantastic I can keep running through this and everything's going to be great now suppose that I wanted to answer this for loop and maybe jump to this log function I don't really care about stepping through this I get how it works how do I get out of this for loop if I try and step out or hit shift at 11 it's actually going to enter the whole function I don't want to do that I just want to kind of keep running the for loop and then stop here how do I do that well it's pretty simple all you have to do is put a breakpoint on where you want to stop next and if I hit f5 or press the continue button up here it's actually going to run my program until it hears the next breakpoint which in this case is this log function so by this point he considers the memory that used to make up this C variable is set to o it's actually still active that memory still there even though we've gone out of scope and we'll talk about that in the future but the memory of sets the very last character the word hello if we bring back our program you can see it's printed up that entire hello word and then we're about to execute this hello world log by hit f10 we're going to jump to the next line of code here it's going to print hello world now we've actually paused execution of this program because we had a breakpoint here I just hit f10 so if I press ENTER here nothing is actually going to happen I need to hit f5 and then our program will close because it is going to still detect that Enterprise so that's it a fantastically simple overview of basic debugging that's going to be a lot more through this but what I just showed in this video is going to be the basis of how we actually debug our code remember a program is really just made up of memory even the instruction pointer which is where in our program we actually are executing code and the actual code that we're executing all of that is stored in memory so being able to view our memory is really all we have and really all we need and by setting breakpoints it lets us pause our program at a given time at a given line of code and actually inspect it and take a look to see what all of our variables are set to which of course is going to be incredibly useful when you're running code I hope you guys enjoyed this video if you did please hit that like button let's see if we can beat our like record I don't know I think it's about 800 let's just let's just let's just smash that you can follow me on Twitter and Instagram I've been posting some pretty cool photos on Instagram lately so you just get you're just not going to want to miss that at all and if you really like this series you can support me on patreon comm forth that's the channel now the cool thing about this is by doing so you'll get access to early drafts of videos and the cool thing about those early drafts is not everything in the draft makes it to the final video to this so you get see stuff that might be cut from the final video exclusive and as well as that of course you are supporting this series and you're enabling me to make more of these videos more often which is pretty awesome hope you guys have a great day I'll see you in the next video goodbye [Music] [Music]

Channel: The Cherno

Views: 269,548

Rating: 4.9596519 out of 5

Keywords: thecherno, the, cherno, project, thechernoproject, c++, how c++ works, learn c++, c++ tutorial, game, programming, development, engine, game programming, game development, how to make a game, tutorial, source, code, complete, game engine, how to make a game engine, opengl, glfw, C (Programming Language), debugging, debug

Id: 0ebzPwixrJA

Length: 19min 19sec (1159 seconds)

Published: Mon May 15 2017