I'm just being introduced to C++, and want to know a basic question....
What happens when using C++? Is there anywhere I can see a working example? Textbooks break it down, segment by segment. I would really like to SEE what happens.
ANY suggestion would be appreciated. Hope MY question is not too vague.
Thanks!
You get into the office around 8:30am, get some tea, and you sit down and run a program called an IDE. It lets you type code with the keyboard, such as:
(*m_pHopeThisIsntNull)->doIt();
You can then hit F5 and the code runs and you find out it doesn't work the way you expected. Pretty soon it's 5:30pm.
If you are trying to learn C++, you cannot just read from the textbook -- programming is learned best through hands-on practice. You should get a C++ compiler and run through the textbook examples yourself.
When I use C++, other programmers bow down to me because of my awesomeness. But that's just my experience.
Sounds like a short session with your TA (at an American university, this is the graduate student who helps with the hands-on stuff, does the grading, etc., as a help to the professor) is in order. Get him/her to show you how to use whatever IDE (integrated development environment) your class is requiring/suggesting. Or wait for your lab session, where you will learn this.
You can use a debugger to execute your program step by step, looking at the variables. If that's not enough, debuggers can also show you the a disassembled version of the machine code along with the processor's registers.
Would that help?
You are using C++! your browser is written in C++!
If you want to see it step by step:
Set a breakpoint at the first line and start in debug (F5 in Visual Studio). You can step through the program step-by-step and see what's going on with varying granularity (Step Over or Step Into - usually F10 and F11 in Visual Studio). Stepping into will follow a function call whereas F10 will call it, and step forward over it after it returns.
If you want to see what's going on at a lower level you can use disassemble on your code.
I've used Visual Studio/Windows stuff here b/c that's what I'm most used to but these things are in every major C++ IDE I've seen.
Related
I've used a few profilers in the past and never found them particularly easy. Maybe I picked bad ones, maybe I didn't really know what I was expecting!
But I'd like to know if there are any 'standard' profilers which simply drop in and work? I don't believe I need massively fine-detailed reports, just to pick up major black-spots. Ease of use is more important to me at this point.
It's VC++ 2008 we're using (I run standard edition personally). I don't suppose there are any tools in the IDE for this, I can't see any from looking at the main menus?
I suggest a very simple method (which I learned from reading Mike Dunlavey's posts on SO):
Just pause the program.
Do it several times to get a reasonable sample. If a particular function is taking half of your program's execution time, the odds are that you will catch it in the act very quickly.
If you improve that function's performance by 50%, then you've just improved overall execution time by 25%. And if you discover that it's not even needed at all (I have found several such cases in the short time I've been using this method), you've just cut the execution time in half.
I must confess that at first I was quite skeptical of the efficacy of this approach, but after trying it for a couple of weeks, I'm hooked.
VS built in:
If you have team edition you can use the Visual Studio profiler.
Other options:
Otherwise check this thread.
Creating your own easily:
I personally use an internally built one based on the Win32 API QueryPerformanceCounter.
You can make something nice and easy to use within a hundred lines of code or less.
The process is simple: create a macro at the top of each function that you want to profile called PROFILE_FUNC() and that will add to internally managed stats. Then have another macro called PROFILE_DUMP() which will dump the outputs to a text document.
PROFILE_FUNC() creates an object that will use RAII to log the amount of time until the object is destroyed. Both the constructor of this RAII object and the destructor will call QueryPerformanceCounter. You could also leave these lines in your code and control the behavior via a #define PROFILING_ON
I always used AMD CodeAnalyst, I find it quite easy to use and gives interesting results. I always used the time based profile, in which I found that it cooperates well with my apps' debug information, letting me find where the time is spent at procedure, C++ instruction and single assembly instruction level.
I used lt prof in the past for a quick run down of my C++ app. It works pretty easy and runs with a compiled program, does not need and source code hooks or tweaks. There is a trial version available I believe.
A very simple (and free) way to profile is to install the Windows debuggers (cdb/windbg), set a bp on the place of interest, and issue the wt command ("Trace and Watch Data"). Check out MSDN for more info.
Another super simple and useful profiling workflow that works on any programming languages is to comment out blocks of codes. After commenting out all of them, uncomment some and run your program to see the performance. If your program starts to run very slow when some code has been uncommented, then you'll probably want to check the performance there.
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Have you used any of the C++ interpreters (not compilers)?
Hi,
I am currently learning C++ and a beginner in programming in general. I've been trying to write some code to a few programming problems from the book I'm using. What I find is that often I make mistakes in what I write and those mistakes come up when the program is run. Its usually quite obvious where in the program I've gone wrong when there is regular output. But in a long computation I'm often not sure why a particular code has acted a certain way. I've also looked at Python recently. Python works with an interpreter, which can take any piece of Python code and compute its output.
I was wondering if there was something similar for C++. Right now when I want to check a line or block of code I have to comment out a lot, save it, compile it, and then run it from a command line. And I have to do that many times for a single error until I've solved it. Is there a way to type code into an active terminal which would run code and show me output? What would be better still would be a way to select a block of code (like you select text) or multiple blocks (to see how a function is being handled) within the IDE and click run to run just that block of code and see its output without having comment out irrelevant lines or to save the file. The compiled code could just reside in memory.
CINT is a c & C++ interpretter that accepts nearly all valid C++. Unfortunately many Linux distros do not offer it, and you'll probably have to build it from source... and that is a non-trivial task.
Typically a debugger is used to step through code line by line, starting at a chosen breakpoint, and keep watch of all variables/values.
Unit testing is a technique to test smaller pieces of code.
A stepping debugger, as found in most IDEs will help you with this.
Here (for example) is a description of how to set the Execution point in In Visual Studio, which sounds like what you want to do.
For certain situations, the "Immediate Window" may be of use to you. It allows you to type in expressions to evaluate immediately.
Rather than just running individual lines independently, or relying on print statements to tell you the state of whatever variables you have decided to print, you can use the debugger to run to the point of interest (where you will have set a breakpoint), then you can examine the state of any in-scope variables, or even alter the normal flow of the program.
There are some solutions that try to do this - the ones I know are Ch and TextTransformer.
However, I doubt that this works very well. C++ is not at all designed to run as an interpreted language.
One of the problems is that C++ is very, very hard to parse. And this makes it very hard to provide certain types of tools that are usual for other languages. For example, I don't think there is any C++ refactoring tool that really works well.
C++ is a compiled language not like python. But there are few c/c++ interpreters out there but not sure about their features. Check these out: Ch interpreter and CINT
If you really want to learn c++ please do not use the c/c++ interpreters.
If you insist on using a interactive interpreter there is since a long time CINT which is the default interpreter used in the ROOT project. It got better over the years, but still has only limited capabilities when dealing with templates. Also, there is a move to replace it with a JIT compiling interpreter based on clang inside the ROOT project.
If I were you I would learn how to run compiler and an interactive debugger like suggested in some comments already.
I've used a few profilers in the past and never found them particularly easy. Maybe I picked bad ones, maybe I didn't really know what I was expecting!
But I'd like to know if there are any 'standard' profilers which simply drop in and work? I don't believe I need massively fine-detailed reports, just to pick up major black-spots. Ease of use is more important to me at this point.
It's VC++ 2008 we're using (I run standard edition personally). I don't suppose there are any tools in the IDE for this, I can't see any from looking at the main menus?
I suggest a very simple method (which I learned from reading Mike Dunlavey's posts on SO):
Just pause the program.
Do it several times to get a reasonable sample. If a particular function is taking half of your program's execution time, the odds are that you will catch it in the act very quickly.
If you improve that function's performance by 50%, then you've just improved overall execution time by 25%. And if you discover that it's not even needed at all (I have found several such cases in the short time I've been using this method), you've just cut the execution time in half.
I must confess that at first I was quite skeptical of the efficacy of this approach, but after trying it for a couple of weeks, I'm hooked.
VS built in:
If you have team edition you can use the Visual Studio profiler.
Other options:
Otherwise check this thread.
Creating your own easily:
I personally use an internally built one based on the Win32 API QueryPerformanceCounter.
You can make something nice and easy to use within a hundred lines of code or less.
The process is simple: create a macro at the top of each function that you want to profile called PROFILE_FUNC() and that will add to internally managed stats. Then have another macro called PROFILE_DUMP() which will dump the outputs to a text document.
PROFILE_FUNC() creates an object that will use RAII to log the amount of time until the object is destroyed. Both the constructor of this RAII object and the destructor will call QueryPerformanceCounter. You could also leave these lines in your code and control the behavior via a #define PROFILING_ON
I always used AMD CodeAnalyst, I find it quite easy to use and gives interesting results. I always used the time based profile, in which I found that it cooperates well with my apps' debug information, letting me find where the time is spent at procedure, C++ instruction and single assembly instruction level.
I used lt prof in the past for a quick run down of my C++ app. It works pretty easy and runs with a compiled program, does not need and source code hooks or tweaks. There is a trial version available I believe.
A very simple (and free) way to profile is to install the Windows debuggers (cdb/windbg), set a bp on the place of interest, and issue the wt command ("Trace and Watch Data"). Check out MSDN for more info.
Another super simple and useful profiling workflow that works on any programming languages is to comment out blocks of codes. After commenting out all of them, uncomment some and run your program to see the performance. If your program starts to run very slow when some code has been uncommented, then you'll probably want to check the performance there.
I'm working as a TA in an introductory programming class, and the students tend to submit their programs as either one line, or without any indentation. Is there any tool that allows me to insert indents and things like that automatically? (We're using C++ and VisualStudio)
You're after a pretty printer. I'd suggest Googling for C++ pretty printer, and looking for something that meets your requirements (price, platform).
As an aside, you may find that deducting marks for poorly formatted code will work just as well. Students need to learn that good code layout is an important part of writing maintainable code.
Rather than answering your question I will advise:
Don't let them do that.
Making their code readable for human beings is a part of programming, and you are fully justified in grading them on it. You might want to point them at the pretty printers listed in the other answers, however. Just to be nice.
Select the entire file (Ctrl-A) and then hit Ctrl-K Ctrl-F, which is essentially format the entire document.
EDIT: Of course in Visual Studio IDE
There is a gnu program called indent, usually shipped with linux but also available here (gnu indent) and available under Cygwin.
However, you are using VS, so you could use it to format code. They have hidden the feature just a bit: Edit -> Advanced -> Format Document, or Control/E, D.
If you need to do this in batch mode, try using astyle, also available in the Cygwin installer.
In Vim it's gg=G.
Using Microsoft Visual Studio 98, Microsoft Visual C++ 6.0 SP6
When running under the debugger, there's only one problem. If I pause the program and resume, everything's fine.
The problem? When I hit a breakpoint, my program stops. But not in a good way; execution halts, I'm thrown out of debug mode into edit mode. All's fine until a breakpoint is hit. And I know it's hitting the breakpoint - I see a flash of the little yellow arrow pointing at the right line of code, local variables in the inspect window and the call stack in that window. And then I'm staring at the editor.
This happens in all projects.
I've uninstalled and re-installed MSVC6. It didn't help.
I'm about to start over on a new PC; before I go that far, anyone know what I've done to this one?
Note: MSVC6 is not my choice, but there are reasons. It's the tool I work with. And, we get to target NT4, so given 2008 can't target NT4 and 2005 has issues with MFC and NT4, MSVC6 it is.
Stop beating on VC6. It's old. The STL was updated in 1996 from HP code written in 1994. C++ was ratified in 1998.
What is the code doing when you are breaking? Can you reduce the situation into a simple test. When I try that I usually find the cause. If you can do that so it still happens then I'll take a look at it for you. I too am unfortunate enough to use VC6 for my day to day work.
Visual C++ Express 2008 can't be used in certain situations.
The first thing I would check is if this project does the same thing on other machines. If not, it could be your box is heading south. If not it's the VC6 project itself.
Typically I get goofiness with the debugger when my program is doing something with the hardware, especially the video.
I would recommend turning off parts of your program until you figure out what part is causing this. If your program is small and not doing much it might be that the project is corrupted and needs to get rebuilt. Make a new project from scratch and put your files and settings back in by hand.
Is it specific to the app you're working on or do all breakpoints in any app break the debugger?
Is anything different if you attach the debugger manually after launching the app normally?
Is the device running out of memory and therefore gives up the ghost when it requires the additional memory to stop at the breakpoint?
Is the device running out of memory and therefore gives up the ghost when it requires the additional memory to stop at the breakpoint?
No, there's over a gig of RAM to go, and even more of virtual memory.
I haven't used MSVC6 in years, but I remember the debugger basically being a flaky piece of crap. Things like this would regularly happen for no apparent reason because it just didn't like your code that day.
In addition to the debugger being a flaky piece of crap, the rest of it was too.
It's STL implementation isn't threadsafe, it doesn't support very much of the C++ standard, and the IDE is sorely lacking in niceties.
I'm pretty sure you also just simply can't use any versions of the Platform SDK from the last 5 years because it's too old to grok them. Not a good thing.
You'd be mad to keep using it when there is Visual C++ Express 2008 which you can download for free.