C / C++ / MFC

14-May-24 20:12

Hi there,

i have a question regarding C++ "language updates", to phrase properly what i want to know:
We currently have an external employee that codes C++ Libraries for us, which are used for "drivers" to ensure communication via Ethernet, USB and Bluetooth.
Those libraries are currently only available as 32 Bit dll's and therefore created a discussion after we found out that in some cases we would as well need them as 64 Bit.

To get to the point, said collegue also mentioned, that those libraries are ensuring a downwards compatibility to run on systems below windows 10 (which is our current limit of support), namingly they run even on Windows XP and probably further down, written with VS 2005 iirc.

Since i am .NET developer i can not really grab the necessity for doing so, nor estimate the potential "risks, flaws or performance" related topics comming up with that compatibility.

So i want to ask you if my concerns are correct or totally wrong, when it comes to using "very old" C++ instead of modernizing it and only ensuring runtime compatibility to "current" OS'es.
I personally feel that, since C++ get's updated every now and then, there must be a reason for doing so, as well as ofc improving the final produce that get's spit out by the compiler if your using newer (not newest) C++ Versions.

As a bonus, if someone could take the time to answer this as well, would you suggest, think about or deny switching code parts into C# and .NET which probably could be switched due to framework functionalities where we can rely on the stuff microsoft already has built in there?

As a note: We leave aside the fact that nobody else from the team would have hardware to continue coding or even compile this old stuff.

In any case, thanks alot for reading and / or answering.

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CPallini23hrs 54mins ago

CPallini

23hrs 54mins ago

This is really a broad topic.
I am only able to just write down few observations.

C++ language updates are not bug-fixes: they improve the language. If you are going to start from scratch a new project then using modern C++ is a real advantage. On the other hand, migrating an old big (working) project could be painful.

If you need a 64bit DLL, you colleague could probably build it without using newest C++ features. Maybe he can, at the same time, keep the existing 32bit DLL, two builds of the same code.

If Microsoft provides me the same functionality my mates code do, by no means I would continue using the latter.

Does the compatibility argument applies also to your .NET code? I mean, DLL compatibility with old OSs is useless if you cannot run the application on such systems.

My two cents.

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

HobbyProggy5hrs 12mins ago

5hrs 12mins ago

Thanks for the answers, that lit up some dark corners for me.

His proposal is to do simply convert the necessery stuff for 64 bit aswell so he'll provide both for us, not changing or modernizing anything.

That's what i would have guessed, an example given, we have code for BLE communication in such a library, i know that Microsoft API or respectivly .NET has a lot of Code and Features provided for BLE communication. SO my idea was, since he knows both worlds, to take the effort and convert to .NET, at least the things that are possible, he wasn't happy...

No, i hope i mentioned it but our application is bound to another external application that standardises things. Therefore we are only supporting Win 10 and 11 because said "Frame Application" is only running on those two.

Thanks again for your answer Smile | :)

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Maximilien23hrs 39mins ago

Maximilien

23hrs 39mins ago

If you switch to 64 bits, you need to update the whole thing, including external libraries.

IMO, it's not worth it to convert to 64 bits unless you have real reasons for it (large datasets, hardware requirements... )

HobbyProggy wrote:
We leave aside the fact that nobody else from the team would have hardware to continue coding or even compile this old stuff.

lol.

At that point, it's more a business decision than a technical decision.

Your company needs to decide if they want to spend money maintaining old code on old compilers or move everything to a recent compiler and making sure everything is continuously up to date

Good luck.

CI/CD = Continuous Impediment/Continuous Despair

HobbyProggy5hrs 5mins ago

5hrs 5mins ago

Thanks, i may need that Unsure | :~

To answer your first statement, it is required for us to support 64bit and 32Bit, with .NET it's easy -> Compile for Any CPU and done. I know it's more complicated in C++.

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k505420hrs 4mins ago

k5054

20hrs 4mins ago

As another has pointed out, the changes to C++ are mostly language extensions. For example, before C++-11, there was no auto or ranged for loops. Some of the language updates do address some defects in the standard, either clarifying the language or addressing a corner case.

Two things stand out:
1) going from 32 bit to 64 bit is rarely as simple as just changing the compiler flags. You may find that, particularly if you need to access hardware, you need to adjust data types. For example a long is 4 bytes in 32 bit land, but 8 bytes in 64 bit land, and if you're using structs you may need to adjust padding.
2) You seem to have a "key man" reliance. Worse, the key man is an external entity. Hopefully, you have an escrow arrangement so that in extremis, you're not in the situation where you have to stat from scratch.

It's not clear why the libs should need to be compatible with older versions of Windows. One reason might be is that the entity providing the library has other clients that need it. If you're the only client, then it might be time to review the deliverables, and update contracts/expectations accordingly.

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

HobbyProggy5hrs 7mins ago

5hrs 7mins ago

Thanks for that.

Yep, i just started there quite fresh as well but it seems i am, because of the tasks i was assigned to, the one that finally starts to clean up some old things. And yes, it'll be fun if something unexpected happens.

I'll keep the last bit in mind and will address this task to my superior.

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jschell11hrs 13mins ago

jschell

11hrs 13mins ago

HobbyProggy wrote:
to ensure communication via Ethernet, USB and Bluetooth.

As described all of those currently exist without customization. One might also wonder if this custom stuff is secure. Specifically how is be being tested to insure that it is secure and will remain so.

HobbyProggy wrote:
windows 10 (which is our current limit of support)

Windows 10 runs on 64 bit systems but it also runs on 32 bit systems.

HobbyProggy wrote:
We leave aside the fact that nobody else from the team would have hardware to continue coding or even compile this old stuff.

Presumably the company at least has the source code.

And yes there are risks to the company in not insuring continuity in case there are problems.

HobbyProggy5hrs 1 min ago

Can this be the cause of a memory leak

5hrs 1 min ago

jschell wrote:
As described all of those currently exist without customization. One might also wonder if this custom stuff is secure. Specifically how is be being tested to insure that it is secure and will remain so.

Yep... Uhm ... exactly one of the first things i was asking when i heard that, on the plus side i was able to read the whole BLE traffic with a sniffer when i was asked to measure and verify time needed for updates over ble.

jschell wrote:
Windows 10 runs on 64 bit systems but it also runs on 32 bit systems.

Yep, i should have mentioned we need both.

jschell wrote:
Presumably the company at least has the source code.
And yes there are risks to the company in not insuring continuity in case there are problems.

I am also asking the question because i want to ensure that we will not be screwed if something funny happens.
All the info will be used to lay out a plan and strategy to not fall off the edge.

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Calin Negru9-May-24 2:50

9-May-24 2:50

for(int i=0;i<3;i++)
{
vector<thing*> * Nodes = new vector <thing*>();
thing * Athing = new thing();
Nodes->push_back(Athing);
//do stuff
}

do I need to delete the vector once the work is done or this is not required?
How about the things stored inside the container, do I need to delete those too or calling clear() is enough.

for(int i=0;i<3;i++)
{
vector<thing*> * Nodes = new vector <thing*>();
thing * Athing = new thing();
Nodes->push_back(Athing);
//do stuff
Nodes->clear();
delete Nodes;
}

modified 9-May-24 9:22am.

Victor Nijegorodov9-May-24 3:05

Victor Nijegorodov

9-May-24 3:05

Calin Negru wrote:
do I need to delete the vector once the work is done?
for(int i=0;i<3;i++)
{
vector<thing*> * Nodes = new vector <thing*>();
thing * Athing = new thing();
Nodes->push_back(Athing);
//do stuff
Nodes->clear();
delete Nodes;
}

Yes, you do.
Since you created it (vector) with new then you need to delete the vector once the work is done

Calin Negru9-May-24 3:37

9-May-24 3:37

What happens if I don’t delete the vector, will that cause a memory leak or it’s just allocated memory that is not used and takes extra space. The program doesn’t break with an error when I do source code version No 1
I have unexpected behavior somewhere else in my program and I was wondering if this could be the cause of it.

modified 9-May-24 10:43am.

k50549-May-24 4:32

k5054

9-May-24 4:32

With a memory leak, the memory footprint of the running process increases over time. If the conditions that lead to the leak are encountered often enough, the process will eventually run out of available memory, usually causing an exception of some sort. Unless you're in a very specialized environment, the memory associated with the process gets released when it exits. That means that the overall memory on the system doesn't get incrementally consumed over time. So you really only run the risk of the one process running out of memory, not the system as a whole. I hope I've explained that clearly enough.

Some system calls (and some user written functions!) use this to their advantage. On the first call they will allocate some memory, and then reuse it on successive calls. With no cleanup routine, they just rely on the program exit to do the memory release. That's why you might get notice of memory in use at exit when running a program under a memory diagnostic tool like Valgrind. When you trace back to where the memory was allocated, it might be inside something like fopen().

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

Calin Negru9-May-24 4:49

9-May-24 4:49

Thanks k5054 I think I understand. What I described in the first example is a memory leak but probably is not causing problems elsewhere.

k50549-May-24 5:51

k5054

9-May-24 5:51

If by "not causing problems elsewhere" you mean it's not affecting other processes, that's mostly true. You can, of course, run into an Out Of Memory (OOM) situation, where all the RAM and swap is marked as "in use", and Bad Things start happening. Assuming you've got a 64 bit OS with lots of RAM and swap configured, (heck, even a 32 bit OS with good Virtual Memory), that's only likely to happen if you've got a lot of memory allocated.

As a rule of thumb, you should clean up memory when it's no longer needed. Think of it like craftsmanship. A piece of Faberge jewelry shows attention to detail from both the back and the front. Freeing up unused memory is part of the attention to detail, just like closing files after use, for example.

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

Mircea Neacsu9-May-24 3:23

Mircea Neacsu

9-May-24 3:23

On top of what Victor said, look into using std::unique_ptr instead of "naked" pointers. Something like this:

C++

auto Nodes = new std::vector< < std::unique_ptr<Thing> >;
Nodes->push_back( std::make_unique<Thing>() ); 
//do stuff
delete []Nodes;

Edit:
It is a bit unusual to "new" vectors. Given they can grow dynamically, in most cases you would write something like:

C++

std::vector<<std::unique_ptr <Thing> >nodes;
nodes.push_back (std::make_unique<Thing>( /*constructor params go here*/ ) );
/* node[0] is a (unique) pointer to Thing */

// do more stuff

When nodes goes out of scope all Things get deleted automatically.

Mircea

modified 9-May-24 9:41am.

CPallini9-May-24 3:28

CPallini

9-May-24 3:28

Yes, you have to explicitly delete the vectors you allocated using new.
But that's not enough.

Try running the following code

C++

#include <iostream>
#include <vector>

using namespace std;

class thing
{
public:
  thing(){cout << "thing ctor\n";}
  ~thing(){cout << "thing dtor\n";}
};

int main()
{

  for(int i=0;i<3;i++)
  {
    vector<thing*> * Nodes = new vector <thing*>();
    thing * Athing = new thing();
    Nodes->push_back(Athing);
    //do stuff
    Nodes->clear();
    delete Nodes;
  }
}

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

Calin Negru9-May-24 4:53

9-May-24 4:53

Thank you guys for your feedback. I think I understand what a memory leak is now.