Base types and pointer arrays - C / C++ / MFC Discussion Boards

Re: C++

Richard MacCutchan8-Jul-21 21:10

Richard MacCutchan

8-Jul-21 21:10

C++

if((finalNumericGrade >= 83 ) & (finalNumericGrade < 90 ))

If you reach this statement the grade must be less than 90, because you already checked that in the previous statement. So all you need is

C++

if(finalNumericGrade >= 83)

And similar for the following tests.

But putting all your code into main like that makes it so much more difficult to debug. Split the different parts out into functions to make it easier to see where your errors may be.

Re: C++

charlieg17-Aug-21 11:38

charlieg

17-Aug-21 11:38

Yeah, that might go through a C++ compiler, but it's not really C++. I just didn't want to pile on.

OP - debugger is your friend.

Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...

"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759

Help me to convert all to C++ (stdio.h)

WEI SHEN KOK7-Jul-21 3:47

WEI SHEN KOK

7-Jul-21 3:47

#include<iostream>
using namespace std;
int main()
{
    const int b=14;
    const float f=0.20;
    cout<<"----------------"<<endl;
    cout<<"BOOK LOAN SYSTEM"<<endl;
    cout<<"----------------"<<endl;
    cout<<"Enter the number of books  : ";
    int n;
    cin>>n;
    cout<<"\nEnter the days of the loan : ";
    int l;
    cin>>l;
    cout<<"\n-------------------------------------"<<endl;
    cout<<"Days overdue                : ";
       if(l>b){
    cout<<l-b;
    cout<<"\nFine                        : RM "<<(l-b)*(f)*n;
        }
}

Re: Help me to convert all to C++ (stdio.h)

Victor Nijegorodov7-Jul-21 4:30

Victor Nijegorodov

7-Jul-21 4:30

Do you mean in this snippet was used some other than C++ language? Confused | :confused:

Re: Help me to convert all to C++ (stdio.h)

Dave Kreskowiak7-Jul-21 5:46

Dave Kreskowiak

7-Jul-21 5:46

Did you mean to say "Help me convert this code I found on the internet to C so I can turn it in as my own work?"

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Seriously, go read these articles.

Dave Kreskowiak

Re: Help me to convert all to C++ (stdio.h)

Maximilien7-Jul-21 9:41

Maximilien

7-Jul-21 9:41

it's already C++.

What are you wanting ? classes ?

I suggest using meaningful variable names instead of b or f or n.

CI/CD = Continuous Impediment/Continuous Despair

Re: Help me to convert all to C++ (stdio.h)

Stefan_Lang7-Jul-21 21:16

Stefan_Lang

7-Jul-21 21:16

If you mean to replace std::cout and std::cin with stdio.h functions, then look up the usage of printf() and scanf(), e. g. at C Library - <stdio.h> - Tutorialspoint[^]

If you mean to convert everything to C, you also may need to remove the const qualifiers depending on the exact C compiler (and version) you are using.

GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)

Base types and pointer arrays

Richard Andrew x645-Jul-21 18:26

Richard Andrew x64

5-Jul-21 18:26

I'm trying to create an array of pointers to a common base class, but each pointer in the array will point to a different derived class instance. This is a 64-bit application.

Here's the critical portion of my code: (Unnecessary detail has been removed.)

Intellisense is warning me that the second pointer assignment (to the second element in the array) will cause a buffer overrun.

It says,

"C6386: Buffer overrun while writing to 'this->m_Members': the writable size is 'this->m_MemberCount*8' bytes, but '16' bytes might be written."

I have never come across this warning before, and I wanted to ask the community if there is something obviously wrong with the code that I'm not seeing.

C++

m_MemberCount = 7;

CGsUCharType* m_s_b1 = new CGsUCharType();  // All of these "Type" classes are derived from CGsTypeBase
CGsUCharType* m_s_b2 = new CGsUCharType();
CGsUCharType* m_s_b3 = new CGsUCharType();
CGsUCharType* m_s_b4 = new CGsUCharType();

CGsUShortType* m_s_w1 = new CGsUShortType();
CGsUShortType* m_s_w2 = new CGsUShortType();
CGsULongType* m_S_addr = new CGsULongType();

CGsTypeBase** m_Members = new CGsTypeBase*[m_MemberCount]; // Is this the correct way to create an array of pointers?

m_Members[0] = m_s_b1;
m_Members[1] = m_s_b2; // This line has the warning about the buffer overrun.
m_Members[2] = m_s_b3;
m_Members[3] = m_s_b4;
m_Members[4] = m_s_w1;
m_Members[5] = m_s_w2;
m_Members[6] = m_S_addr;

The difficult we do right away...
...the impossible takes slightly longer.

Re: Base types and pointer arrays

Daniel Pfeffer5-Jul-21 20:56

Daniel Pfeffer

5-Jul-21 20:56

Your code should work (Intellisense is a little confused here), but may I suggest using std::vector instead:

C++

#include <vector>
 ...

 std::vector<CGsTypeBase*> m_Members(m_MemberCount);

This will ensure that your array is properly constructed and is destructed when it goes out of scope.

You may also wish to look into storing smart pointers (rather than raw pointers) in the vector. This can help ensure that they are destructed at the right time, as well.

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

Re: Base types and pointer arrays

Richard Andrew x646-Jul-21 3:55

Richard Andrew x64

6-Jul-21 3:55

Thank you for taking the time to respond. I will consider using vector instead.

The difficult we do right away...
...the impossible takes slightly longer.

Re: Base types and pointer arrays

Richard MacCutchan5-Jul-21 20:59

Richard MacCutchan

5-Jul-21 20:59

What are the definitions of CGsTypeBase and CGsUCharType?

[edit]
I built this short program and it compiled and linked successfully:

C++

struct CGsTypeBase
{
    char foo[8];
};
struct CGsUCharType : CGsTypeBase
{
    wchar_t foo[8];
};

struct CGsUShortType : CGsTypeBase
{
    uint16_t foo[8];
};
struct CGsULongType : CGsTypeBase
{
    long foo[8];
};


int main(
    int		argc,
	char*   argv[]
	)
{
    int m_MemberCount = 7;

    CGsUCharType* m_s_b1 = new CGsUCharType();  // All of these "Type" classes are derived from CGsTypeBase
    CGsUCharType* m_s_b2 = new CGsUCharType();
    CGsUCharType* m_s_b3 = new CGsUCharType();
    CGsUCharType* m_s_b4 = new CGsUCharType();

    CGsUShortType* m_s_w1 = new CGsUShortType();
    CGsUShortType* m_s_w2 = new CGsUShortType();
    CGsULongType* m_S_addr = new CGsULongType();

    CGsTypeBase** m_Members = new CGsTypeBase*[m_MemberCount]; // Yes, this is the correct way to create an array of pointers

    m_Members[0] = m_s_b1;
    m_Members[1] = m_s_b2; // No warnings here
    m_Members[2] = m_s_b3;
    m_Members[3] = m_s_b4;
    m_Members[4] = m_s_w1;
    m_Members[5] = m_s_w2;
    m_Members[6] = m_S_addr;

	return 0;
}

So how does that differ from your code?

[/edit]

modified 6-Jul-21 3:54am.

Re: Base types and pointer arrays

Richard Andrew x646-Jul-21 3:56

Richard Andrew x64

6-Jul-21 3:56

Yes, my code compiles and links successfully too. I guess it's just intellisense that has a problem. Thank you for your response.

The difficult we do right away...
...the impossible takes slightly longer.

Re: Base types and pointer arrays

CPallini5-Jul-21 21:03

CPallini

5-Jul-21 21:03

A wild guess: the intellisense does not think (like, instead, you assume) that m_MemberCount is equal to 7.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Re: Base types and pointer arrays

Richard Andrew x646-Jul-21 3:57

Richard Andrew x64

6-Jul-21 3:57

That's what I think as well. I'm glad to know someone else has the same idea. I did come across a few posts about that warning being incorrect.

The difficult we do right away...
...the impossible takes slightly longer.

Re: Base types and pointer arrays

jschell17-Jul-21 10:09

jschell

17-Jul-21 10:09

Richard Andrew x64 wrote:
CGsTypeBase** m_Members = new CGsTypeBase*[m_MemberCount]; // Is this the correct way to create an array of pointers?

As others have pointed out the your solution works because of the way the memory lays down.

In the above you have a declaration of a variable which has a type. And you also give the variable a value. But the declaration of the variable is a pointer. Just a pointer. Not a pointer to an array. So when intellisense sees you use it as an array it goes basically 'pointer + 1' isn't going to work. It does works because of the value and not the declaration.

I believe there is a declaration form that allows you to specify the form that would make intellisense happy but been a long time since I attempted C++ so I will leave it to someone else to come up with the form that makes the array specific.

Re: Base types and pointer arrays

Richard Andrew x6417-Jul-21 13:39

Richard Andrew x64

17-Jul-21 13:39

Thanks for your input. I appreciate you taking the time to post.

The difficult we do right away...
...the impossible takes slightly longer.

Literal for a short

Richard Andrew x645-Jul-21 11:47

Richard Andrew x64

5-Jul-21 11:47

We can put a "u" after a numeric literal to indicate that it should be compiled as an unsigned int.

Or we can put "ll" to indicate that it should be compiled as a long long.

But what is the correct character to indicate that it should be compiled as a short?

The difficult we do right away...
...the impossible takes slightly longer.

Re: Literal for a short

Greg Utas5-Jul-21 12:24

Greg Utas

5-Jul-21 12:24

There isn't one. You'd have to cast it: short(0).

EDIT: I prefer to use int16_t or uint16_t rather than assuming that's what I'll get. But if you're working with code that already uses short, go ahead and use it.

Robust Services Core | Software Techniques for Lemmings | Articles
The fox knows many things, but the hedgehog knows one big thing.

Re: Literal for a short

Richard Andrew x645-Jul-21 12:55

Richard Andrew x64

5-Jul-21 12:55

Thanks, Greg.

The difficult we do right away...
...the impossible takes slightly longer.

Debug Application from Service

Richard Andrew x643-Jul-21 14:16

Richard Andrew x64

3-Jul-21 14:16

Does anyone know if it's possible to debug a user application from a Windows service, or if there is something that prevents this?

I suppose I could find out by just trying it, but I'd rather not waste time creating and installing a skeleton service just to see that it's not possible.

I'm hoping someone might know one way or the other.

The difficult we do right away...
...the impossible takes slightly longer.

Re: Debug Application from Service

Daniel Pfeffer3-Jul-21 17:24

Daniel Pfeffer

3-Jul-21 17:24

Services run, by default, under the LocalService account, which is an extremely limited account. You can set your service to run as one of the predefined LocalService, NetworkService, or LocalSystem accounts, OR you can create your own account, assign privileges to it, and run your service under that account.

Note that use of LocalSystem is not recommended, as it essentially gives your service access to anything on the platform!

If you are running a debugger under a service, you may wish to allow the service to interact with the user.

Service User Accounts - Win32 apps | Microsoft Docs
LocalService Account - Win32 apps | Microsoft Docs
LocalSystem Account - Win32 apps | Microsoft Docs
NetworkService Account - Win32 apps | Microsoft Docs

Interactive Services - Win32 apps | Microsoft Docs

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

Re: Debug Application from Service

Richard MacCutchan3-Jul-21 21:11

Richard MacCutchan

3-Jul-21 21:11

It rather depends on what you mean, and how you think a service could attach itself to a user application, and what information it could collect.

Re: Debug Application from Service

Joe Woodbury4-Jul-21 17:14

Joe Woodbury

4-Jul-21 17:14

When writing a service, I always add a way to pass a command line parameter to run the app in debug mode as a console app. Many examples do the same thing.

In other circumstances, you can attach to the service. Without the proper architecture, this can run into timeout issues.

Re: Debug Application from Service

Richard Andrew x645-Jul-21 6:25

Richard Andrew x64

5-Jul-21 6:25

Thanks for your response. I was asking more about using the service as a debugger and having it attach to a user process.

The difficult we do right away...
...the impossible takes slightly longer.

Multiple view ports in single window using opengl and c++

Member 107421151-Jul-21 23:15

Member 10742115

1-Jul-21 23:15

Hi,

Can some one help me?. I need to make a window with multiple viewports like in 3DS MAX with c++, Each viewport must be rendered with OpenGL with separate mouse actions

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.