C / C++ / MFC Discussion Boards

Randor 21-Dec-20 13:01

Randor

21-Dec-20 13:01

Hi,

I think on Linux the LD_LIBRARY_PATH environment variable is used to find shared libs. You might be looking for ldconfig and /etc/ld.so.conf if you are on Linux.

Re: Configure Script Issue

k505421-Dec-20 17:42

k5054

21-Dec-20 17:42

You don't say whether make completes successfully or not. The compiler flags given tell the compiler where to find the pieces to buld the program. If the compile has completed successfully, but when you try to run the program you get a message

"error while loading shared libraries: <libname.so>: cannot open shared object file: No such file or directory

then the problem is at runtime, not compile time. As Randor notes, you can tell the link-loader where to find the library with LD_LIBRARY_PATH

k5054@localhost$ LD_LIBRARY_PATH=/usr/local/lib64 myprog arg1 arg2

sets LD_LIBRARY_PATH for the given command. To set for a single session do

k5054@localhost$ export LD_LIBRARY_PATH=/usr/local/lib64
k5054@localhost$ myprog arg1 arg2

You can add that to your shell's .profile file. and it will be set every time you log in. If you want to set this up permanently for all users ont the system, then as root create a file /etc/ld.so.conf.d/local.conf containing the single line

/usr/local/lib64

Now, as root, run ldconfig, and you should be able to run your program from any login, without needing to set LD_LIBRARY_PATH in your .profile or per session/per command.

you can check what libraries are being loaded using the ldd command

<
k5054@localhost$ ldd /bin/bash
        linux-vdso.so.1 (0x00007ffebf5f6000)
        libtinfo.so.6 => /lib/x86_64-linux-gnu/libtinfo.so.6 (0x00007f7ec6539000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f7ec6533000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f7ec6341000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f7ec66b5000)

If the link-loader can't find a library, it will show

libsomelib.so => not found

Keep Calm and Carry On

Writing a Factory Design Pattern Program with separate Header Files and Class Implementations

Litu Sahoo17-Dec-20 12:26

Litu Sahoo

17-Dec-20 12:26

Hi,

I am trying to learn factory design pattern in c++, writing a program with separate header files and their class implementations in .cpp files. But i am facing problem. I was trying the ShapeFactory from where we implement Circle and Rectangle.

invalid new-expression of abstract class type 'Circle'
invalid new-expression of abstract class type 'Rectangle'

But i am getting these errors and also few other errors. Can someone please help on this.

Regards
Litu

Re: Writing a Factory Design Pattern Program with separate Header Files and Class Implementations

Gerry Schmitz17-Dec-20 19:27

Gerry Schmitz

17-Dec-20 19:27

"new" ... you can't instantiate an "abstract" class; you need to subclass it first or use an existing derived class.

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

Re: Writing a Factory Design Pattern Program with separate Header Files and Class Implementations

Richard MacCutchan17-Dec-20 23:36

Richard MacCutchan

17-Dec-20 23:36

Your Shape class should be the only abstract one. Circle and Rectangle should be complete classes that inherit Shape. There is a very good set of articles on factory patterns by @SneshPrajapati here on CodeProject, starting with Factory Patterns - Simple Factory Pattern[^].

Beginning C++ for Windows Application

chipp_zanuff13-Dec-20 6:06

chipp_zanuff

13-Dec-20 6:06

i wanna ask, what is the best environment for learning C++ for windows application? e.g. Win32 API, Qt, etc...

also, could anyone suggest what's the best e-books for references?

Re: Beginning C++ for Windows Application

Gerry Schmitz13-Dec-20 6:19

Gerry Schmitz

13-Dec-20 6:19

When (really) learning, they usually start you with Notepad and a command line compiler. The "environment" can suck up most of your time (and disk space).

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

Re: Beginning C++ for Windows Application

Richard MacCutchan13-Dec-20 6:32

Richard MacCutchan

13-Dec-20 6:32

It depends on what you are trying to learn. If you know C++ then Win32 should be fairly easy. But if you do not know C++ then that is what you need to start with.

Here is a starter for C++: Learn C++[^]

And one for Windows: EFNet #Winprog[^]

cmath.h compile error

Haakon S.9-Dec-20 21:20

Haakon S.

9-Dec-20 21:20

I am compiling some old legacy code with MFC. For this line in cmath.h I get an error:

NODISCARD _Check_return_ inline float round(_In_ float _Xx) noexcept /* strengthened */ {
    return _CSTD roundf(_Xx);
}

With first round statement highlighted I get this message:

C2062 type'int' unexpected

Re: cmath.h compile error

CPallini9-Dec-20 21:39

CPallini

9-Dec-20 21:39

You should inspect the calling code, I believe (the compiler provides full information with the error message).

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

Re: cmath.h compile error

Haakon S.10-Dec-20 0:51

Haakon S.

10-Dec-20 0:51

I don't understand that. It is a compile error in a core library file. I am not allowed to change it. Why would the calling function have anything to say?

Re: cmath.h compile error

CPallini10-Dec-20 1:16

CPallini

10-Dec-20 1:16

Quote:
Why would the calling function have anything to say?
Quote Selected Text

With very high probability the calling code is wrong (possibly making incorrect assumptions on the called function, it passes the wrong type). Maybe a previous implementation of the library had relaxed checks on calling code correctness.

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

Re: cmath.h compile error

Greg Utas10-Dec-20 1:04

Greg Utas

10-Dec-20 1:04

Use your development environment (VS or whatever) to check that there is a #define for each the following:

NODISCARD
_Check_return_
In
_CSTD

And if you're using C instead of C++, noexcept could be the problem. But I can't say, because I only write C++.

EDIT: D'Oh! | :doh:

type 'int' unexpected suggests that the caller is passing an int, not a float.

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Re: cmath.h compile error

Haakon S.10-Dec-20 1:58

Haakon S.

10-Dec-20 1:58

There are plenty of _Check_return_ statements that work.

If there is something wrong with the calling function, I should get a compile error when compiling the cpp file where the function is called? This is an error from inside the include file cmath.h.

Three errors reported, underscore is the highlighted error indication.

Line 210
_NODISCARD _Check_return_ inline float round(_In_ float _Xx) noexcept /* strengthened */ {
return _CSTD roundf(_Xx);
}
Line 446
_NODISCARD _Check_return_ inline long double round(_In_ long double _Xx) noexcept /* strengthened */ {
return _CSTD roundl(_Xx);
}
Line 663
_GENERIC_MATH1(round)

It seems I am not allowed to alter any include file, so I can not experiment with commenting the functions out, etc.

Re: cmath.h compile error

Greg Utas10-Dec-20 2:19

Greg Utas

10-Dec-20 2:19

Check if round is also defined somewhere else, and check that _GENERIC_MATH1 is actually defined. Beyond that, I don't know.

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

Re: cmath.h compile error

David Crow10-Dec-20 2:13

David Crow

10-Dec-20 2:13

I would be inclined to look at the preprocessor output to see what all of those non-standard "types" are.

"One man's wage rise is another man's price increase." - Harold Wilson

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"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

Re: cmath.h compile error

Randor 10-Dec-20 2:46

Randor

10-Dec-20 2:46

Hi,

I am going to point out that you are almost certainly looking at the wrong code location. The C2062 error usually really does mean the 3 letters 'int' were unexpected while parsing the code.

Look around for an int that is declared wrong.

Re: cmath.h compile error

Richard MacCutchan10-Dec-20 3:21

Richard MacCutchan

10-Dec-20 3:21

Is that the full text of the error message? Also what are the few lines either side of that definition?

Re: cmath.h compile error

Daniel Pfeffer10-Dec-20 3:53

Daniel Pfeffer

10-Dec-20 3:53

Your compiler should have an option to send the output of the preprocessor into a file. Using Visual C/C++, this option is /P, and the output file has an extension of .i .

Run your code through this, and look for cmath.h in the .i file. Then look for the definition of the round() function. You will see what the compiler thinks the round() function is, and your problem should then be obvious. Smile | :)

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

Re: cmath.h compile error Problem solved

Haakon S.11-Dec-20 4:07

Haakon S.

11-Dec-20 4:07

Hi and thanks for all help.

When I put

#include <cmath>

right under #include stdafx.h it compiled. Don't ask me exactly why. It may be a conflict between math.h and cmath that was solved in this way.

Regards, Haakon S.

Re: cmath.h compile error Problem solved

Randor 11-Dec-20 8:04

Randor

11-Dec-20 8:04

So...

You said that your compiler gave you an error in cmath.h

Haakon S. wrote:
For this line in cmath.h I get an error:

Which you solved... "by including cmath.h"

Confused | :confused:

Re: cmath.h compile error Problem solved

Haakon S.11-Dec-20 23:56

Haakon S.

11-Dec-20 23:56

I honestly don't know what is going on.

Some files had #include <math.h>. Removing this did't help. It reported error in cmath anyway.

When googling "cmath error c2062" I see that others have had the same problem.

Anyway, it seems that I have found the solution.

C++ class question

pkfox8-Dec-20 6:40

pkfox

8-Dec-20 6:40

Ok C++ is not mt my main language so please bear with me.

For my question I will use this class

class BillingDates
{
public:
    BillingDates(std::string InputFile);
    void ProcessDates();
    rapidjson::Document doc;
    std::string InputFile;
    std::string YearStartDate;
    std::string YearEndDate;
    std::string BBFDate;
    std::string BillIssueDate;
    std::string BillIssueDateLong;
    int CurrentFinancialYear = 0;
    std::ifstream InputStream;
};

And in my main program I declare a pointer and an object to the class thus

BillingData *bData;
BillingData bData2;

I can then create my pointer so

bData = new BillingDates("path to my file");

how can I create an instance for bData2 ?
I know I can do it like this

BillingData bData2("path to my file");

but that will create a new var and not use my previously declared var.
Hope this makes sense

"I didn't mention the bats - he'd see them soon enough" - Hunter S Thompson - RIP

Re: C++ class question

Mircea Neacsu8-Dec-20 6:51

Mircea Neacsu

8-Dec-20 6:51

If your code looks exactly like posted, compiler will slap you with an error on bData2 line because you don't have a default constructor. You can:
1. Modify the constructor to default to an empty string: BillingDates(std::string InputFile = std::string()) and handle the case when InputFile is the empty string.
2. Create an additional default constructor: BillingDates()

If you need to move data from bData to bData2 you might need a copy constructor: BillingDate (const BillingDate& other).

Mircea

Re: C++ class question

pkfox8-Dec-20 7:17

pkfox

8-Dec-20 7:17

Hi and thanks for replying but the problem I have is I don't know the path to my input file until later in the program

"I didn't mention the bats - he'd see them soon enough" - Hunter S Thompson - RIP

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