CodeProject Latest postings for C / C++ / MFC

HOW TO ANSWER A QUESTION

Chris Maunder — Mon, 13 Jul 2009 08:37:00 GMT

Apologies for the shouting but this is important.

When answering a question please:

Read the question carefully
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar
If a question is poorly phrased then either ask for clarification, ignore it, or mark it down. Insults are not welcome
If the question is inappropriate then click the 'vote to remove message' button

Insults, slap-downs and sarcasm aren't welcome. Let's work to help developers, not make them feel stupid.

cheers,
Chris Maunder

The Code Project Co-founder
Microsoft C++ MVP

HOW TO ASK A QUESTION

Chris Maunder — Fri, 13 Feb 2009 04:19:00 GMT

For those new to message boards please try to follow a few simple rules when posting your question.

Choose the correct forum for your message. Posting a VB.NET question in the C++ forum will end in tears.
Be specific! Don't ask "can someone send me the code to create an application that does 'X'. Pinpoint exactly what it is you need help with.
Keep the subject line brief, but descriptive. eg "File Serialization problem"
Keep the question as brief as possible. If you have to include code, include the smallest snippet of code you can.
Be careful when including code that you haven't made a typo. Typing mistakes can become the focal point instead of the actual question you asked.
Do not remove or empty a message if others have replied. Keep the thread intact and available for others to search and read. If your problem was answered then edit your message and add "[Solved]" to the subject line of the original post, and cast an approval vote to the one or several answers that really helped you.
If you are posting source code with your question, place it inside <pre></pre> tags. We advise you also check the "Encode HTML tags when pasting" checkbox before pasting anything inside the PRE block, and make sure "Ignore HTML tags in this message" check box is unchecked.
Be courteous and DON'T SHOUT. Everyone here helps because they enjoy helping others, not because it's their job.
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No advertising or soliciting.
We reserve the right to move your posts to a more appropriate forum or to delete anything deemed inappropriate or illegal.

cheers,
Chris Maunder

The Code Project Co-founder

Microsoft C++ MVP

C++20 UNORDERED_MAP OBJECT WITH CLASS FUNCTIONS FROM DLL AS VALUE

Oscar Kogosov 2023 — Tue, 23 Jul 2024 06:37:00 GMT

2 Errors:
a) Lambda does not not with static var, so I must to work wwith bind
b) I try to invoke functions of class from DLL, saved in unordered_map object and fall.If to invoke functions of class not from DLL it is work properly.
How can this problem be solved?


	file UnorderedMapFunctions.cpp
<pre lang="C++">#include <iostream>
#include <unordered_map>
#include <functional>
#include <windows.h>

#include "..\\Geometry\\Geometry.h"
using namespace std;

namespace NS
{
  class Math
  {
  public:
    int Sum(int x, int y) { return x + y; }
    int Sub(int x, int y) { return x - y; }
    int Mul(int x, int y) { return x * y; }
    int Div(int x, int y) { return x / y; }
  };
}
using namespace NS;

int main()
{
  unordered_map<string, function<int(int, int)>>* mydata = new unordered_map<string, function<int(int, int)>>;
  Math* m = new Math;
 
  // Using lambda functions to bind member functions
  (*mydata)["sum"] = [m](int x, int y) { return m->Sum(x, y); };
  (*mydata)["sub"] = [m](int x, int y) { return m->Sub(x, y); };
  (*mydata)["mul"] = [m](int x, int y) { return m->Mul(x, y); };
  (*mydata)["div"] = [m](int x, int y) { return m->Div(x, y); };
  /*
  //Geometry* g = new Geometry;
  (*mydata)["circle"] = [g](int x, int y) { return g->Circle(x, y); };
  (*mydata)["rectangle"] = [g](int x, int y) { return g->Rectangle(x, y); };
  */
  //==============================================================
  string fullname_dll = "Geometry";
  HINSTANCE hInst = LoadLibraryA(fullname_dll.c_str());
  if (hInst == nullptr)
  {
    cout << "Error: [FuncImport] wrong name " << fullname_dll.c_str() << endl;
    return false;
  }
  typedef void (CALLBACK* CreateInstanceFunc)(unordered_map<string, function<int(int, int)>>* mydata);
  string CreateFuncName = "CreateInstance"; 
  CreateInstanceFunc CreateInstance = (CreateInstanceFunc)GetProcAddress(hInst, CreateFuncName.c_str()); 
  if (CreateInstance == nullptr)
  {
    cout << "Error: wrong name " << fullname_dll << endl;
    FreeLibrary(hInst);
    return false;
  }
  CreateInstance(mydata);
  cout << "Imported " << fullname_dll.c_str();
  FreeLibrary(hInst);
  //==============================================================
  // Invoke by 'key' functions, saved in 'mydata'
  // it is right! 
  for (const auto& [k, v] : *mydata)
    std::cout << "Key: " << k << " Value: " << v(3, 5) << std::endl;
  //===================================
  auto it = mydata->find("circle");
  if (it != mydata->end())
   // Exception thrown: read access violation.
   // fault in functional.h line 920
   // it->second.vfptr = addr(??? ??? ??? ??? ???)
    cout << "\nKey: " << it->first << " Value: " << it->second(4, 2) << std::endl;
  else
    cout << "Error\n";
  //===================================

  delete m;
  delete mydata;
  return 0;
}

//=============================================================
2 Dll files: Geometry.h, Geometry.cpp
file Geometry.h

C++

#pragma once
#include <iostream>
#include <unordered_map>
#include <functional>
#include <windows.h>

#ifdef GEOMETRY_EXPORTS
#define GEOMETRY_API __declspec(dllexport)
#else
#define GEOMETRY_API __declspec(dllimport)
#endif

using namespace std;
namespace NS
{
  class GEOMETRY_API Geometry
  {
  public:
    Geometry();
    int Circle(int x, int y);
    int Rectangle(int x, int y);
  };
  extern "C" void  GEOMETRY_API  CreateInstance(unordered_map<string, function<int(int, int)>>* mydata);
  extern "C" void  GEOMETRY_API  Cleanup();
}

file Geometry.cpp

C++

#include "pch.h"
#include "Geometry.h"

namespace NS
{
   Geometry* geometryInstance;
  void CreateInstance(unordered_map<string, function<int(int, int)>>* mydata)
  {
    geometryInstance = new Geometry;
    // Can't capture a static variable in a lambda
    //(*mydata)["circle"] = [geometryInstance](int x, int y) { return geometryInstance->Circle(x, y); };
    //(*mydata)["rectangle"] = [geometryInstance](int x, int y) { return geometryInstance->Rectangle(x, y); };

    (*mydata)["circle"] = bind(&Geometry::Circle, geometryInstance, placeholders::_1, placeholders::_2);
    (*mydata)["rectangle"] = bind(&Geometry::Rectangle, geometryInstance, placeholders::_1, placeholders::_2);
  }
  Geometry::Geometry() {}
  int Geometry::Circle(int x, int y) { return 3.14 * x * x; }
  int Geometry::Rectangle(int x, int y) { return x * y; }
  void Cleanup()
  {
        delete geometryInstance;
        geometryInstance = nullptr;
  }
}

glReadPixels wrong values

etechX2 — Mon, 22 Jul 2024 02:30:00 GMT

hi,
I am not sure what is missing.
I created 16 bit grayscale buffer and pass it to glDrawPixels(..), then in mouse function callback I try to read the first pixel with glReadPixels(0,0,1,1,GL_LUMINANCE ,GL_UNSIGNED_SHORT,pixUnSigShort) and is wrong. Tried also GL_LUMINANCE16.

C program(homework)

Member 16311074 — Fri, 19 Jul 2024 06:36:00 GMT

Prepare the following strings in advance as an array. Be sure to write everything in full-width characters.
"The difference between being 18 and 81. 18 years old is the one who drowns in love, 81 years old is the one who drowns in the bath. 18 years old is the one who runs down the road, and vice versa.
The person running is 81 years old. An 18-year-old has a fragile heart, and an 81-year-old has a fragile bone. I'm 18 years old and my heart can't stop pounding.
He is 81 years old and can't stop the plane. An 18-year-old can choke on love, and an 81-year-old can choke on rice cakes. I'm concerned about the deviation value
I am 18 years old, and I am 81 years old and concerned about my blood pressure and blood sugar levels. An 18-year-old who doesn't know anything yet, an 81-year-old who doesn't remember anything anymore.
An 18-year-old who is looking for himself, and an 81-year-old who is looking for everyone else. "
- Then have the user enter a search string. Search characters can be up to 10 characters.
・Then, have the user enter a replacement string. Replacement characters can be up to 10 characters.
- Perform a prefix match search on the above string and replace all hit strings.
- After replacing, output the result to the screen. If there are no conversion candidates, "Nothing to convert" is displayed.(if the searched string is in more than 1 place on the original string, the replacement will replace all of it)

Community Verified icon

How to use QUERY_CHANGES_VIRTUAL_DISK_RANGE when HyperV backup

DingHuaming — Thu, 18 Jul 2024 04:39:00 GMT

Does anyone know the use of QueryChangesVirtualDisk ?
I have call the function successfully.
But how to use the QUERY_CHANGES_VIRTUAL_DISK_RANGE?

Code change request (From Linux To Windows)

Member 16143694 — Mon, 15 Jul 2024 07:30:00 GMT

Dear somebody,

I have in trouble with some code.

Q1) ==> Actually my reqeust.
I want to build this open source "https://github.com/ChengranAA/QuickNii" but something failed in
nifticlib and zlib. The owner maybe not familiar with Windows build.
So I've found new ones.

https://github.com/NIFTI-Imaging/nifti_clib

For windows git bash method...

https://github.com/addisonElliott/nifticlib

this man tells original Windows CMake method but...
I'm already exhausted in CMake gui use!!!!

Is there anybody who can help EASY&Simple~~ Windows develop source code view????
I want to change it but...there some problems and not clean changed~

For the
Q2) C# wpf code can wrap(import code) well the C++ codes in VS2022?? (Just for usual programming)

If this question is stupid or something violated codeproject policy, I will delete it or I will
agree to automatically delete from codeproject admin.

C++ DLL Debugging - Visual Studio 2022

PaulS_UK — Tue, 09 Jul 2024 18:20:00 GMT

Can someone please tell me how I can debug a C++ DLL from within Tradestation 10 by attaching VS2022 to the Tradestation process?

I can compile a DLL successfully and call a function from it for display within a Tradestation workspace. After a LOT of time spent browsing around on various MicroSoft learning pages etc etc, I have arrived at the following method but cannot get Visual Studio 2022 to load symbols or recognize the required .PDB file(s).

To complicate matters the DLL must be a release version and reside in the Tradestation system file for it to work with Tradestation.  It is my understanding that this is ok so long as the relevent .pdb files are available to enable debugging.  Here is my methodology so far:

1. Compile the C++ DLL in Visual Studio 2022 in RELEASE mode as specified for use in tradestation.
2. Set post build to copy MyDLL.dll and MyDLL.pdb to C:\Program Files (x86)\TradeStation 10.0\Program
3. Indicator using function from MyDLL.dll plots ok - great!
4. Set breakpoint in C++ code within function in Visual Studio 2022: breakpoint shows no errors.
5. Attempt to debug in release mode in VS 2022 by attaching Tradestation process using indicator/MyDLL to be debugged: Debug -> Attach to Process... -> ORPlat.exe

++++ Now things do not go to plan ++++++++

6. MyDLL.dll not listed in Modules window
7. Numerous messages appear in the Modules window such as:
ORPlat.exe C:\Program Files (x86)\TradeStation 10.0\Program\ORPlat.exe Cannot find or open the PDB file.
8. MyDLL.dll shows up as being loaded ok using DebugView

Compiler settings in VS2022 are:

/ifcOutput "Release\" /GS /GL /analyze- /W3 /Gy /Zc:wchar_t /Zi /Gm- /Od /Fd"Release\vc143.pdb" /Zc:inline /D "WIN32" /D "NDEBUG" /D "_WINDOWS" /D "_USRDLL" /D "GLOBALVARIABLE23_EXPORTS" /D "_WINDLL" /D "_UNICODE" /D "UNICODE" /errorReport:prompt /WX- /Zc:forScope /Gd /Oy- /Oi /MT /FC /Fa"Release\" /EHsc /nologo /Fo"Release\" /Ot /Fp"Release\Future DLL.pch" /diagnostics:column 

Am I flogging a dead horse here? Is it impossible to debug MyDLL.dll from within Visual Studio by attaching it to the Tradestation process (ORPlat.exe)? If it is not possible (such as debugging only from within Tradestation; how do you attempt serious debugging in complex C++ code within your MyDLL.dll functions?

Any help on this greatly appreciated!

Cheers

TextBox File Open

Robert Johnson 2023 — Mon, 08 Jul 2024 07:42:00 GMT

0

I need to read the TextBox input, my username and password work as below, but the file input and file output require another step to convert a string that can open the files.

I've tried every example I can find, cstring numerous times.I can't believe no one uses a textbox to open a file. Why can't i get an answer? Will someone please read this question and answer it. I see that some questions get numerous answers and I can't even get one answer. Please help me!

THESE 2 BELOW WORK private: System::Void usernameTextBox_TextChanged(System::Object^ sender, System::EventArgs^ e) { msclr::interop::marshal_context context; std::string myUsername = context.marshal_asstd::string(usernameTextString); }

private: System::Void passwordTextBox_TextChanged(System::Object^  sender, System::EventArgs^  e) {
     msclr::interop::marshal_context context;
     std::string myPassword = context.marshal_as<std::string>(passwordTextString);
     }
THESE 2 BELOW NEED AN ADDITIONAL LINE OF CODE TO OPEN THE FILES private: System::Void myInfileTextBox_TextChanged(System::Object^ sender, System::EventArgs^ e) { msclr::interop::marshal_context context; std::string myInfile = context.marshal_asstd::string(myInfileTextString); }

private: System::Void myOutfileTextBox_TextChanged(System::Object^  sender, System::EventArgs^  e) {
     msclr::interop::marshal_context context;
     std::string myOutfile = context.marshal_as<std::string>(myOutfileTextString);
     }

timer does not start

etechX2 — Thu, 27 Jun 2024 06:20:00 GMT

Hi,
in my MFC DLL, pMyDLLCWnd is pointer to a class driver from CWnd.
When CDialog is linked to DLL, timer starts.
When console is linked to DLL, same timer does not start.
pMyDLLCWnd->Settimer(ID,t,NULL)
DLL has wm_timer message handler.

AfxRegisterWndClass crashes when called again

etechX2 — Thu, 13 Jun 2024 06:07:00 GMT

Hi,

In my MFC project, I get crash as follows:

1. i call MyCreate() then MyUnCreate()
2. calling MyCreate() the second time, causes crash at AfxRegisterWndClass below.

sudo code provided:

CMyCwndSub is derived from CWnd.

in another file:

CMyCwndSub *p;

C++

void MyCreate()
{
    //in here code looks for Window with title "MyWndWin".

	p->new CMyCwndSub;
	CString m = AfxRegisterWndClass(0);       //crashes in this line the 2nd time called.
	p->CreateEx(0, m, -T"MyWndWin",0,0,0,0,0,NULL,0);
	
	.
	.
	.
}

C++

void MyUnCreate()
{
delete p;
p = NULL;
}

Inserting a user defined key in a C++ map

Amrit Agr — Mon, 10 Jun 2024 18:23:00 GMT

Hi Guys,

I have recently came across one scenario where I have to insert a user defined key in a c++ map. that class looks like this

class key
{
int id;
string name;
};

map is like map<key,int>

I'll overload "operator<" function and will sort out based on "id" which will works fine, but the condition is like, if there are 2 entry with same ID but with a different name, for ex. {"50", Jack} and {"50", John}

As both the values have SAME ID and different name, map should make an entry for both.

Only in the case of combination of same ID and same name, it shouldn't allow the entry.

bool operator<(key& temp)
{
if(id < temp.id)
{
return true;
}
if( id == temp.id)
return name < temp.name;
}

its not working properly, its overriding the last entry if same ID is there.

Please help me out

C++, epiphanies, article content ideas

honey the codewitch — Sat, 08 Jun 2024 06:28:00 GMT

Disclaimer: What I'm about to talk about is C++ implementation details. C++ compilers aren't *necessarily* implemented the way I describe in theory, but in practice they virtually all are - at least the major ones, AFAIK.

C++ is very "lexical" in how it works.

The bones of the OOP, method overloading, and template instantiations are implemented in part through name mangling, which is fundamentally lexical vs having a different, say, integer or binary key for each of the above.

The template instantiations work like a mail merge, but with "smart" template parameters (by smart I mean, not simply lexical but type aware, compiler resolved). The actual template code is basically search and replaced, but template resolution is "smart" (similar to how i used the word above) in that it can resolve recursively and stuff, so it's a bit more complicated than strict search replace, but it's close.

C++ in many ways (but not all ways) is C with syntactic sugar.

C++ OOP isn't special. It's basically C with a combination of name mangling, and hiding the first (implicit) this argument

consider the following

C++

#include <stdio.h>

class foo {
    int m_bar;
public:
    foo(/*foo* this*/) : /*this->*/m_bar(0) {

    }
    int bar(/*foo* this*/) const { return this->m_bar; }
    void bar(/*foo* this, */ int value) { this->m_bar = value; }
};

typedef struct _foo_c {
    int bar;
} foo_c_t;

void foo_foo_foo_c_t(foo_c_t* handle) {
    // : m_bar(0)
    handle->bar = 0;
}
int foo_bar_foo_c_t(foo_c_t* handle) {
    // return this->bar;
    return handle->bar;
}
void foo_bar_foo_c_t_int(foo_c_t* handle, int value) {
    // this->bar = value;
    handle->bar = value;
}

int main(int argc, char** argv) {
    foo foo_cpp;
    foo_cpp.bar(42);

    foo_c_t foo_c;
    foo_foo_foo_c_t(&foo_c);
    foo_bar_foo_c_t_int(&foo_c,42);

    printf("foo_cpp: %d, foo_c: %d\n",foo_cpp.bar(),foo_bar_foo_c_t(&foo_c));

    return 0;
}

That's C++ and its rough equivalent as C code, and the C is similar to how the C++ resolves internally.

I feel like understanding that helped me greatly understand C++.

I'm wondering if any other C++ developers out there had a similar epiphany about the language that helped them understand it better, and what it was.

Part of it is I was thinking of compiling an article about this, but the above isn't enough by itself.

I'm hoping to add more content, but maybe some of you who have had similar epiphanies about the language could inspire more content along this vein. If so, please put it in a reply. Thanks!

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

I never fail to be impressed by this

honey the codewitch — Fri, 07 Jun 2024 15:44:00 GMT

Disclaimer: The following is intended to run in embedded environments that may not have a compliant STL if they have the STL at all. Some of this code could be replaced on systems with The STL to use std:: functionality.

Anyway, it's code I wrote, but it's not my code that really impresses me about this, but rather the C++ compiler.

C++

static_assert(pixel_type::template equals<gfx::rgb_pixel<16>>::value,
                          "this code needs to be ported for your display format");

That's a compile time check to determine if a pixel format is exactly the same as the specified pixel format.

Not impressed yet?

Those pixel formats are arbitrarily defined:

C++

// creates an RGB pixel by making each channel 
// one third of the whole. Any remainder bits
// are added to the green channel
template<size_t BitDepth>
using rgb_pixel = pixel<
    channel_traits<channel_name::R,(BitDepth/3)>,
    channel_traits<channel_name::G,((BitDepth/3)+(BitDepth%3))>,
    channel_traits<channel_name::B,(BitDepth/3)>
>;
// creates an RGBA pixel by making each channel 
// one quarter of the whole. Any remainder bits
// are added to the green channel
template<size_t BitDepth>
using rgba_pixel = pixel<
    channel_traits<channel_name::R,(BitDepth/4)>,
    channel_traits<channel_name::G,((BitDepth/4)+(BitDepth%4))>,
    channel_traits<channel_name::B,(BitDepth/4)>,
    channel_traits<channel_name::A,(BitDepth/4),0,(1<<(BitDepth/4))-1,(1<<(BitDepth/4))-1>
>;
// creates a grayscale or monochome pixel
template<size_t BitDepth>
using gsc_pixel = pixel<
    channel_traits<channel_name::L,BitDepth>
>;
// creates a Y'UV pixel by making each channel 
// one third of the whole. Any remainder bits
// are added to the Y' channel
template<size_t BitDepth>
using yuv_pixel = pixel<
    channel_traits<channel_name::Y,((BitDepth/3)+(BitDepth%3))>,
    channel_traits<channel_name::U,(BitDepth/3)>,
    channel_traits<channel_name::V,(BitDepth/3)>
>;

And furthermore

C++

// defines a channel for a pixel
template<
    // the channel name, like channel_name::R
    typename Name,
    // the bit depth
    size_t BitDepth, 
    // the minimum value
    bits::uintx<bits::get_word_size(BitDepth)> Min=0, 
    // the maximum value
#if HTCW_MAX_WORD >= 64
    bits::uintx<bits::get_word_size(BitDepth)> Max= ((BitDepth==64)?0xFFFFFFFFFFFFFFFF:((1<<BitDepth)-1)), 
#else
    bits::uintx<bits::get_word_size(BitDepth)> Max= ((BitDepth==32)?0xFFFFFFFF:((1<<BitDepth)-1)), 
#endif
    // the default value
    bits::uintx<bits::get_word_size(BitDepth)> Default = Min,
    // the scale denominator
    bits::uintx<bits::get_word_size(BitDepth)> Scale = Max
>
struct channel_traits {
    // this type
    using type = channel_traits<Name,BitDepth,Min,Max,Scale>;
    // the type that represents the name
    using name_type = Name;
    // the integer type of this channel
    using int_type = bits::uintx<bits::get_word_size(BitDepth)>;
    // the floating point type of this channel
    using real_type = bits::realx<16<=BitDepth?HTCW_MAX_WORD:32>;
    // the bit depth of this channel
    constexpr static const size_t bit_depth = BitDepth;
    // the minimum value
    constexpr static const int_type min = Min;
    // the maximum value
    constexpr static const int_type max = Max;
    // the default value
    constexpr static const int_type default_ = Default;
    // the scale denominator
    constexpr static const int_type scale = Scale;
    // the reciprocal of the scale denominator
    constexpr static const real_type scaler = 1/(real_type)Scale; 
    // a mask of the int value
    constexpr static const int_type int_mask = ~int_type(0);
    // a mask of the channel value
    constexpr static const int_type mask = bits::mask<BitDepth>::right;
    // constraints
    static_assert(BitDepth>0,"Bit depth must be greater than 0");
    static_assert(BitDepth<=64,"Bit depth must be less than or equal to 64");
    static_assert(Min<=Max,"Min must be less than or equal to Max");
    static_assert(Default>=Min,"Default must be greater than or equal to the minimum value");
    static_assert(Default<=Max,"Default must be less than or equal to the maximum value");
#if HTCW_MAX_WORD >= 64        
    static_assert(Max<=((BitDepth==64)?0xFFFFFFFFFFFFFFFF:((1<<BitDepth)-1)),"Max is greater than the maximum allowable value");
#else
    static_assert(Max<=((BitDepth==32)?0xFFFFFFFF:((1<<BitDepth)-1)),"Max is greater than the maximum allowable value");
#endif
    static_assert(Scale>0,"Scale must not be zero");
};

I don't know of any other language that allows this kind of compile time expressiveness. I wish they did. Sometimes it feels like I'm "in dialogue" with the compiler rather than with the generated/runtime code as with most languages.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Passing a class (pointer) to library - Linux

Salvatore Terress — Fri, 31 May 2024 19:00:00 GMT

I have one more question.
I will try my best to describe the issue and hoping the discussion does not get centered on terminology and RTFM as in the past.
That is not an instruction on how to reply, just a polite request to get real and skip opinions.

( And if you think me saying this is rude...
I am just trying to get of the dime and writing it as politely as I know)

I did have resolved the syntax of "passing the class" , however now I am stuck with WHERE the class should be declared.
In layman terms - the calling object passes a class pointer to the function, which happens to be my own created library. I expect the library function to PROCESS the passed class...
And that is where I am not sure if I have to define / declare the SAME class again - this time in the library.
I did test this using / passing SINGLE variable pointer and it worked OK.

I am not sure what to do when the entire class is passed.
I do not think dupicating the class definition is vise.

(Maybe it needs to be declared as global to the project ?)

Any theoretical help , answer, would be appreciated, I can manage the code...

Cheers

class BT_UTILITY_LIBRARY_EXPORT BT_Utility_Library
{
public:
    // class variable
    // forward declaration ? works here !
    class Test;

    //May31
    QString DEBUG_Process(void);
    QString DEBUG_Process(int *);
    QString DEBUG_Process(class Test *);
    QString DEBUG_Process_Class(class Test *);

    QString REG_EXP_Process(void);

    class Test
    {
       public:
       int a;
       //int b[a];
       QString text;
    }TestPointer;

How C++ manage memory in event driven system ?

Salvatore Terress — Thu, 30 May 2024 14:44:00 GMT

I am trying to improve my C++ skills and could use some advice.
I am using event driven tool - I am not allowed to say the name here -
and my basic question is
if I create an instance of a class which uses a library
should the library by instantiated in class constructor
as a common to all class methods variable
or
be instantiated in each method ( as a local method variable ) as needed ?
Process speed is immaterial, my question is about how is
memory allocated / de-allocated ( managed by C++) during the events.

UPDATE CLOSED error: declaration of anonymous class must be a definition

Salvatore Terress — Sat, 25 May 2024 15:49:00 GMT

This post original subject - error: declaration of anonymous class must be a definition
was caused by this class declaration

<   class REG_EXP                         //regular_expression_class
    {
        int a;
        QString text;
        QString RegExp;
        QString Analyze;
    } TEST_REG_EXP;
/pre>

Search for the symbol "REG_EXP" in the entire project returned no result. 
The conclusion 
it is unknown why the error was posted.
Please consider this matter closed.

UPDATE REPOST BUMP How to construct / build / interpret regular expression ?

Salvatore Terress — Fri, 24 May 2024 16:31:00 GMT

UPDATE
DONE
"Match any number of characters , (from start of the line) , until "new line \n " is reached :

QRegularExpression re( ".*\n");

TODO
match first word only (of each line )
match the entire text (first word of each line )

I am VERY sorry to be such bother, but I am actually looking
for someone / somebody willing to help me to interpret ( read) the Linux
regular expression manual to build the expression.

My task is to
match each and every FIRST word in multi-line string .

I am stuck at

"\w+"

which matches EVERY word in the entire text

I can post my current code when I get
"I am willing help you..."
response

Thank you very much for understanding .

Sal

Okay, real C++ question - who makes use of the auto keyword?

charlieg — Sun, 19 May 2024 11:29:00 GMT

I'm trying to straighten out some pointer "arithmetic" in some existing code. The expressions themselves are overly ambiguous to say the least. In part of my readings, I've come across the "auto" keyword where the compiler deduces what type I need. At least that's what I got from all of the verbiage.

This seems a) dangerous and b) adds another level of mental indirection to what you are trying to accomplish. To me, software needs to be very clear and explicit in what data you are working with and what you intend to do with it. A lot of the "here is how auto will help you" descriptions justify it by saving typing when trying to make use of other classes, templates and the like. It feels like the C++ committee came up with a feature A then added feature B to make using A easier. I'm now doing battle with lambda expressions - another story.

So, in your code - do you make extensive use of auto, and how does it help you?

Charlie Gilley

“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759

Has never been more appropriate.

mfc, vs2022 compatible?

charlieg — Fri, 17 May 2024 17:21:00 GMT

Maybe someone can point me to a reference or provide direct experience. I'm trying to lift a VC6++ application to VS2022. Originally targeted at Xp, this will need to run under Win10 and 11. So, I thought it would also be a good idea to get it into a modern development environment.

Well, the # of warnings I am suppressing is getting concerning, but I understand what the warnings are about. Then I ran into this line of code:

"ON_NOTIFY_REFLECT(NM_CUSTOMDRAW, OnCustomDraw)"

pure mfc macro which generates "....cpp(66): warning C26454: Arithmetic overflow: '-' operation produces a negative unsigned result at compile time (io.5)."

Mousing over the macro, it expands to some hideous expression: "{ 0x004E + 0xBC00, (WORD)(int)((0U - 0U) - 12), 0, 0, AfxSigNotify_v, (AFX_PMSG)(static_cast<void (ccmdtarget::*)(nmhdr*,="" lresult*)=""> (OnCustomDraw)) },"

It's clear why the compiler is alarmed: "(WORD)(int)((0U - 0U) - 12)"

Am I just wasting my time here? I'm going to thunder on, but I'm starting to wonder if I'm going to run into so much nonsense like this that it calls into question if I'll have anything working at the end....

Charlie Gilley

“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759

Has never been more appropriate.