C++ :: Declare A Struct / Class In A File For Local Use But With Internal Linkage?
Mar 15, 2013
I've been wondering about something for a while:
Is it possible to declare a struct/class, in a cpp file, designed for local use, but with internal linkage?
The usecase is that every once in a while, I want to wrap "startXXX+endXXX" function pairs in a simple RAII struct. I just declare the struct in my cpp and use it once.
However, if I do this, (AFAIK), the compiler will generate an entry in the link table, which means I could potentially have link conflicts if I declare the same struct twice in two different cpp files.
Unless I'm mistaken, since the struct is declared in the same cpp that it is used, I wouldn't need external linkage. Is there a way to avoid it?
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Jan 17, 2015
lets say we have a valid class with full implementation, X. can this class be declared as forward in Y header file:
Code: class X;
class Y{
X* m_X;
}
but still be used as regular in the cpp file?
Code:
#include "Y.h"
#incldue "X.h"
T Y::function(){
m_X->doSomething();
}
visual studio prevents me from doing it , I wonder if the standard also says so.
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Dec 8, 2014
I have some code here where I try to declare a struct then pass it as a parameter into a function to do something to it:
Code:
struct _user {
char * initial[3];
int pos;
} user;
int initial_add (struct user * initial_list, int initials, char * buffer) {
[Code] ...
I get the error :
server2.c:15: warning: "struct user" declared inside parameter list
server2.c:15: warning: its scope is only this definition or declaration, which is probably not what you want
[Code] ....
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Mar 9, 2012
I just read and have known for a while that classes are private (members and inheritance) by default and structs are public. But my question then comes what if.. a struct inheriting from a class or a class inheriting from a struct?
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Oct 20, 2013
i've defined an strcuct in .h file and i read its variable in a method in .cpp file ,but i'v got error.
.H file:
class myclass{
public:
struct opt_struct
[Code]....
when i declare the struct without static , it doesn't recognize my struct and with static i face linker error:
Error33error LNK1120: 1 unresolved externals
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Jul 15, 2013
is it possible to don't declare an object for a class and use the function of this class ? i saw a code use this but i cannot find it again .
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Dec 30, 2013
How can I forward declare an inner class?
I currently have this:
Code:
class Enigma
{
public:
Enigma()=delete;
Enigma(char r1,char r2,char r3,char r4, char r5, char r6, char r7, char r8, char r9, char r10);
~Enigma(){delete[] R;}
Enigma(const Enigma& rhs)=delete;
Enigma& operator=(const Enigma& rhs)=delete;
[Code]...
I'd like to be able to define Rotor outside of Enigma, but the compiler complains about incomplete types.
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Jun 27, 2013
Basically, I need to set a variable outside of the constructor and make it accessible to the entire class.
It would need to work something like this:
#include <iostream>
#include <string>
template <typename MT> class CallbackFunction
{
[Code].....
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Aug 23, 2012
i hit the point where i have two class templates that are dependent on each other (in detail, class a stores a pointer of class b), creating a cyclic include issue.
Usually i resolve this with a forward declaration, but i cant seem to figure out how to do it with a template class.In fact, ( i think) i got it to work for this :
Code:
template<typename T>
class a
{
public:
T x;
}
but not for this:
Code:
template<int b>
class b
{
public:
int getb(){return b;}
}
Where the template is not for a specific "type".
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Jul 29, 2013
I wanted to add that the template argument is needed because its a "special case" but if that doesn't work what would be the next best way to solve this problem. I want to be able to declare the const size of the array outside the class far removed from it actually. I'm actually going off this page
[URL] .....
Heres the code
#include <iostream>
template <int F>
class C
{
[Code]....
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Mar 24, 2014
This keeps giving me the error
ecg.h:18:11: error: field "next" has incomplete type
How do I do what I need? It does the same thing whether I use a class or a struct. This is C++ code
struct ECG_node {
double voltage;
clock_t time;
ECG_node next;
[Code] .....
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Mar 19, 2013
I am programming an old-school dungeon crawler and thought it would be cool to get the pc's internal speaker in on the action. While Ive used the BEEP function to nice effect for generating music, how I would go about getting speech out of my internal speaker?
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Sep 11, 2013
My prog name is test and the problem is when i compile it gives error : 'test' is not recognized as an internal or external command,operable program or batch file.
Code:
#include <stdio.h>
#define ISDIGIT(y) ( y >= 48 && y <= 57 )
main( )
}
[code].....
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Nov 26, 2012
The example enable a client to iterate the internal std::vector using being() and end().
Code:
class foo {
public:
typedef std::vector<std::string>const_iterator iter;
iter begin () const;
iter end () const;
[Code] .....
In the future I see the need for this class to be able to control sequence (sorting) and also show a subset of the complete list based on a search parameter.
Using std::sort appear to solve the ability to sort the collection.
How can I return an iterator to the client which only iterates a sub-set of all items in the std::vector?
An example would be, I add this method to the class;
Code:
void find(const std::string& st);
So if the client performs (below) only items in std::vector that contains the character "a" should be possible to iterate.
Code:
foo f;
f.search("a");
One option would be to operate with two collection inside the foo class. One more static containing all items and the other containing the sorted and filtered items. This would lead to some copying but should work. Far from perfect.
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Dec 9, 2014
I am using C++ new/delete operators to allocate/deallocate the buffers. I think for each allocated buffer, there should be an additional info block stores the size and other info about the buffer. How to know more details about this info block? I need to override these two operators and find such an info block is useful to my implementation.
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Oct 15, 2013
I read in another forum that it is bad practice to declare static variables in a header file? Is that true and if so why.
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Aug 1, 2013
I am trying to open a file from local Path by the follwing code
CString csRegExtractFileRemote;
CFileException ef;
CFileStatuscfsStatus;
CFile cfSAP;
csRegExtractFileRemote = "c:SWRemoteFilesample.txt";
[Code] ....
Compilation is success full ,but i am observing that some junk value is there in the path variable. After Reaching If statement cursor went to final return statement ...
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Dec 5, 2013
I'm trying to implement a simple template array class, but when i came into the operator< i actually have to use a template :
my code is something like :
template<typename _Type, std::size_t _Size>
class array {
public :
[Code] ......
but i am having an error of shadows template param 'class _Type' is it w/ the name conflict between the array template parameter and the function template parameter ?
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Jun 21, 2014
I've been working on a path-tracer for some time, and all along I've used structs instead of classes for vectors and matrices. Today I changed all of them to classes instead, changing none of the actual function bodies themselves, and the results were miserable to say the least.
Here's a render form before the change: [URL] ....
And here's the same render after: [URL] ....
Why this is happening, considering that none of the actual function-bodies have been changed, except for what little is needed to make the change from class to struct.
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Apr 28, 2015
I'm making a small MFC module that should generate a report (formatted using HTML) and then display it for a user on schedule at 8:30 AM every day. Pretty straightforward stuff.
I compose my report and then save it as a local HTML file in the CSIDL_APPDATA folder. I then use the following calls to display it using the default web browser (Internet Explorer in this case):
Code:
//Error checks are omitted for brevity
CoInitializeEx(NULL, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);
ShellExecute(NULL, NULL, strSaveFileTo, NULL, NULL, SW_SHOWNORMAL);
This module is run on schedule from the Task Scheduler. (The task is set up to run when a user is logged on, which is all the time for that PC. It is never turned off, put to sleep, etc. That computer has only one user that is never logged off either.)
This works perfectly fine when I test it by setting the task a minute or so in the future. But when the actual task is supposed to run at 8:30 AM, when the user wakes the screen all they see is a blank Internet Explorer page. (Note that if someone refreshes that page by hitting F5, only then my report is shown on the screen.)
So I started looking into it:
1) I checked that the file is properly saved (before calling ShellExecute) by reading it back and by comparing it with the original HTML markup that I saved earlier. It's all correct there.
2) I then checked the power saving options. That computer is set up to show screensaver after 5 minutes and to turn off screen after 25 minutes.
3) The web browser that causes this issue is IE version 11, with the latest updates installed. The operating system is Windows 7 Professional.
And why is IE showing a blank page only when computer is running unattended?
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Jun 23, 2013
while writing code i got a question. For example i created a class named as unit.
Think a simple game, and the unit class will belong the units.İf i give the preferences as private one by one, it will be irregular. For a detailed game; height, weight, race, hair preferences, eyes... Strength, dexterity, charisma, intelligence, wisdom, constution... experience, damage, armor...
and should i use struct to group them? And how to can i use struct at the inside of class as private?
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Sep 4, 2013
I'm trying to learn as much C++ as I can. I was writing a program that mixes linked lists and classes. There is the class "Obj" which only holds an integer called 'data' and the classic "struct node" structure for linked list, but this time the "node" structure will hold an instance of "Obj" Class and the next* pointer.
#include <iostream>
using namespace std;
class Obj {
private:
int data;
public:
[code]....
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Feb 14, 2013
I am making a snake game just to give some context.
//LevelObject.hpp
class LevelObject {
public:
virtual void Update() = 0;
virtual void Draw(Canvas& canvas) = 0;
protected:
Vector3 location_;
[Code] ....
The problem I have is with the Size constructor and the abstract class LevelObject which size is a member of.
The compiler error I get is:
C:Program Files (x86)ProgrammingProjectsUniversityprg_interactivesnakey_takeysrc..inc..incPlayer.hpp|17|warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]|
C:Program Files (x86)ProgrammingProjectsUniversityprg_interactivesnakey_takeysrc..inc..inc..incPlayer.hpp|17|warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]|
[Code] .....
However I do invoke the copy constructor when I pass a variable of type size to the constructor in this line:
size_ = Size(s);
But the problem is that its complaining that the abstract class LevelObject doesn't invoke the constructor, which it shouldn't.
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Mar 16, 2013
Is it any different when using a class in my code. My previous code i define my struct like this
Code: #include <iostream>
#include <fstream>
#include <string>
struct{
[Code] .....
or do i still define it the same way at the top of my code.
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Apr 2, 2014
How to get relative memory address of members of Class or Structure ? I want to auto scan the members of Class/Struct, and show the address/value like the "watch window" in debug mode of popular C/C++ IDE software.
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Oct 2, 2014
I would like to have a unmodifiable standard of WAVEFORMATEX defined as a member of a class of mine. Something like:
class InputTest {
public:
const WAVEFORMATEX StandardWaveFormat;
public:
void TakeInput(WAVEFORMATEX pFormat);
};
Then in my cpp file to hard-code the values:
WAVEFORMATEX InputTest::StandardWaveFormat {
//Instantiate WaveFormat -- PCM standards
StandardWaveFormat.wFormatTag = WAVE_FORMAT_PCM;
StandardWaveFormat.cbSize = 0; //extra information sent over stream. Usually ignored in PCM format.
[Code] ....
I get the following errors starting with the header file:
Error1error C2146: syntax error : missing ';' before identifier 'StandardWaveFormat'
Error2error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
both associated with the "const WAVEFORMATEX StandardWaveFormat; " line.
Here's a link to the WAVEFORMATEX struct: [URL] .....
Then the cpp source code is probably way off. Let me know if you'd like to see the errors associated with that.
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