C++ :: Declaring Variables (Conditional) At Runtime?
Jan 22, 2014
I am looking for a way to declare variables at run time which being a static language shouldn't happen. I will explain my situation.
I am upgrading a legacy program that modifies executables (non malicious). I am trying to add 64bit support.
It is a huge project and I understand the majority of it but my issues with how it handles the input data.
It has a struct that certain parameters of the input file is loaded into:
Code:
typedef struct DATA {
DWORD Size;
IMAGE_NT_HEADERS32 Headers;
} _DATA; *PDATA
etc, etc its a huge list.
My problem lies in the fact that I need to change IMAGE_NT_HEADERS_32 to IMAGE_NT_HEADERS64 at runtime.
That DATA struct gets called at least 110 times during runtime.
How I might tackle this? Having a conditional statement repeated that many times seems ridiculous.
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Oct 21, 2012
I can not set the size of my array while running porgrama. Is there any way to do this in C + +?
---- code ------
#include <iostream>
#include <string>
using namespace std;
[Code].....
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Nov 12, 2012
This is a c program that is failing to compile. The error occurs in the calcLabs() function. The error called out is (btw, I'm using VS 2010): Error4error C2143: syntax error : missing ';' before 'type'
I don't understand why the compiler is not letting me declare variables in the calcLabs() function!
Code:
#include<stdio.h>
#include<stdlib.h>
void calcPercent(double *);
double calcLabs();
double calcExams();
double calcFinal();
char calcLetter(float);
[code]...
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Aug 9, 2013
I really do not see the difference between these two declarations:
int myvariable;
int * mypointer;
It is said that when you define a pointer, instead of containing actual data, it contains a pointer to the memory location where information can be found.
But doesn't the other variable declaration do the same? It obviously doesn't have data either. And it must be stored in a memory location as well. So I do not see the difference.
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Sep 30, 2014
I have created a windows form project in visual studio so that I can use a windows form to interact with the game class that I'm creating, but I'm running into some problems.
For one thing, I would like to be able to call Image::FromFile() one time only during initialization, and store the result in a member variable (called mBGImage). From what I can tell, the variable needs to be of type String^ (this caret symbol is new to me, but I understand it is the "managed code" version of the standard pointer, which would look like String*).
When I try to compile the following code (located in my header file) I get the error :
"error C3265: cannot declare a managed 'mBGImage' in an unmanaged 'BSG::BSGame'".
How can I store the result of Image::FromFile() permanently in my class?
When I try to declare a global variable of type "Image^", I get "error C3145: global or static variable may not have managed type System:rawing::Image ^"
#include "stdafx.h"
using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
[Code] ......
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Jan 25, 2013
i know
Code: (condition) ? true-clause : false-clause
but how do you use an array as the condition, how will the code look?For example i want to write
Code:
string numbers[5] = {"one","two","three","four","five"};
numbers == "one" ? thumb : again; thumb and again will replace something else. Don't worry about them.
how do i say that if the numbers array is representing "one" then it replaces as "thumb", otherwise "again".
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Feb 4, 2014
So I think I am having syntactical problem with my code.
Code:
int main() {
vector<int> ivec;
int score;
[Code] ....
I get an error from my compiler on the ?10th? line (Nested condition line) that says |19|error: invalid operands of types 'int' and '<unresolved overloaded function type>' to binary 'operator<<'|
The purpose of the program is to take input and store it in a vector and then change the value to be between 1-6. I made this for the purpose of learning about nested conditional operations.
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Aug 1, 2014
I am trying to use getline as the conditional for a while loop as seen below.
string filename, guard_name;
int call_number;
vector <Seniority> SeniorityList;
ifstream SeniorityFile;
[Code] ....
However, when I compile the code, I get the following error message on the line with the while loop.
error C2780: 'std::basic_istream<_Elem,_Traits>
&std::getline(std::basic_istream<_Elem,_Traits>
&,std::basic_string<_Elem,_Traits,_Alloc>
&)' : expects 2 arguments - 3 provided
The program will be reading in a .csv file, so I need my program to be able to deal with values separated by commas. Is there a reason why it will not accept that conditional statement?
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Nov 4, 2013
I'm facing a serious problem with udp protocol. I have Master & Slave devices.I did implement the class as the follow pseudo code states
In Master side
while (true)
{
1-send data to slave;
2-get data from slave;
3-apply force;
}
In Slave side
while(true)
{
1-get data from master;
2-if (collision happnes)
send force to the master
}
the problem is in line 2 in Master side. Once I include the line I can't send or receive data. What do you think the problem is?
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Jan 31, 2014
I want to know if it's valid to use and/or when using the conditional operator.
Example:
value = textBox1.Text;
decimal? qty = (value.Equals("0") || value.Equals("0.0")) ? null : (decimal?)decimal.Parse(value);
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Nov 16, 2014
I'm playing with my final year project, building a game boy emulator in C, and I wanted to try out something to streamline my code base. I'm building against Win32, GNU C and Googles Native Client.There are no platform specific headers or functions in use. What I'm trying to do is have a file that conditionally includes the entry point (so _tmain for Windows etc) based on a preprocessor directive being set/not-set.
[note] I realise I could write both entry point classes in one file and use the preprocessor directive in there, but it's not as neat as a single file calling in one or the other. I figure this should work because I can conditionally include headers for Win/NaCl (providing the signatures match, of course).
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Jan 15, 2014
I have the following code:
Code:
while (lineread != "
")
{
getline(ifs,lineread);
}
In essence, it reads an input file, line by line until it hits a line only containing a newline character. So if the input text file is:
27
GC0123456
102905908801170--
2034068010201360
3039077011601400
4043086012901400
504709401400
6051010101400
[code]....
It should exit the while loop after hitting line 6. What happens however is that it goes into a perpetual loop and doesnt exit the while loop upon reading line 6.
What I did was changed the code to:
Code: while (lineread != "*")
{
getline(ifs,lineread);
} and the input file to:
27
GC0123456
102905908801170--
2034068010201360
3039077011601400
4043086012901400
[code]....
and finally it stops after line 6. In this case, merely changing the " " conditional character to a simple asterisk character "*" fixes the problem.
However I wish to keep the input text file as is with the newlines, so how do I make it exit the while loop when detecting a as a line?
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Aug 1, 2014
I'm making a program to draw a trajectory, was using as a basis the tangent, but when I put 90 degrees, the tangent is very large, so I thought of putting an if (angle == 90) did not use the tangent.
the design is right, but after choosing it 90 degrees it stops to draw.
for example
1-30 degrees - draws
2-45 degrees ---- draws
3 draws -90 degrees ---
4-60 degrees --- not drawing
5 --- 80 degrees --- not drawing
*
*
making routine design is presented below:
void Draw() {
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_LINES);
convert(graus);
if (ant){
x=xx;
y=yy;
[code]....
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Nov 24, 2014
I am getting this message from Valgrind, As far as I can see what it points to is initialized. The memory it is referring to is freed in unload and I was not getting this error until after I added the check function. Valgrind was happy. Here is the code and the error message from Valgrind. I am trying to create a spell checker for an assignment for a online class I am taking. I just want to get this table working correctly before I add it to the rest of the program. The code seems to run fine but I have come to see that dos not mean much in C.
#include "hashTable.h"
#include <stdbool.h>
table_node hash_table[TABLE_LENGTH];
bool loaded = true;
//assigning letters a-z to table nodes for buckets
void key_hash_t( )
[Code] ....
Valgrind error:
arortell@gentoo ~/Development/Projects/C_Projects/Data_Structures/HashTable $ valgrind --leak-check=full --track-origins=yes ./hashTable
==11360== Memcheck, a memory error detector
==11360== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==11360== Using Valgrind-3.9.0 and LibVEX; rerun with -h for copyright info
==11360== Command: ./hashTable
[Code] ....
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Apr 10, 2013
I want to do conditional compilation based on whether it is windows 7 or windows 8. Here is the code below.
#if (_WIN32_WINNT >= 0x0602) //Condition to check whether it windows 7 or 8 .Based on this we can load msxml 3 or 6.
#import <msxml6.dll>
#else
#import <msxml3.dll>
#endif
Im building the above code in windows 8 machine.
Issue here is _WIN32_WINNT should have a value 0x0602, it means it is running in windows 8 machine.Instead it has a value 0x0601 (Means it is taking windows version as windows 7 defined in sdkddkver.h).Im not sure after installing windows 8 sdk im not able to see any include or lib files in the path below C:Program Files (x86)Microsoft SDKsWindowsv8.0A . but i can see all include and lib files of sdk version v7.0A available although i did not installed it.
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Jan 10, 2013
I have airport class which should navigate planes, in its list to runways, with method move, theres a method prepare which changes the direction of flight to all planes, always before move is called, move just increments decrement x and y of plane in its list. But after calling two times in row airport->move(), I get screwed and I really dont know wheres the problem. Have I badly initiazed something? Iterator gets invalidated.
Valgrind Stacktrace
Conditional jump or move depends on uninitialised value(s)
==26207== at 0x409601: plane::move() (in /home/xnovak11/Downloads/airport/main)
==26207== by 0x401FBD: airport::move() (in /home/xnovak11/Downloads/airport/main)
==26207== by 0x405FE1: io::start(std::istream&, std:stream&, std:stream&) (in /home/xnovak11/Downloads/airport/main)
This is how I add planes into list in airport
Code:
list<plane*> planes;
list<plane*>::const_iterator planeIterator;
list<plane*>::iterator planeIteratorMoj;
bool airport::addPlane(const plane& p) {
[Code] .....
This is the method where it fails. When I call it once, no problem, after second call I get instead of normal number in cout<<after move<< s1 i get like 8795456 ....
Code:
void airport::move() {
for(planeIteratorMoj = planes.begin(); planeIteratorMoj!= planes.end(); planeIteratorMoj++) {
plane * p1 = (*planeIteratorMoj);
int s,w;
p1->getPosition(s,w);
[Code] .....
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Nov 6, 2014
I am putting a instance o the Vehicle Class inside the constructor of the Calculate Class then calling it later. I get a warning saying the variable is not used and a error when I try to used the functions from the vehicle class saying use of undeclared identifier.
Code:
#include <iostream>
#include "Calculate.h"
#include "Vehicle.h"
#include <fstream>
Calculate::Calculate(){
[Code] ....
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Jun 5, 2013
I am a bit confused about how specific one must be with arguments when declaring a function. I'll show you two functions from the book I'm using to learn C to show you what I mean.
Example 1 (greatest common denominator function):
Code:
void gcd (int u, int v) {
int temp;
printf ( "
[Code] ....
So in that function, there are exactly two arguments, because that's how many arguments the algorithm to find the gcd takes. No problem there, makes sense to me. Then further in the chapter on functions I run into this,
Example 2 (square root function):
Code:
float absoluteValue (float x) {
if ( x < 0 )
x = -x;
return x;
[Code] ....
In this second example, we have a square root function that is preceded by an absolute value function. The absolute value function has the one argument, "float x", however when this function is called within the square root function, the arguments "guess * guess * -x" are passed to it. I'm confused how this absolute value function is working with all of that inside it, when it was originally declared with just "x." The only possibility I can think of is that this expression is treated as a single unit, but I'm not sure.
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Apr 4, 2013
Code:
if (IS_LEAP_YEAR(year))
const int days_per_month[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
else
const int days_per_month[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; Is it ok to declare the array in this manner or is it bad?
And i have to ask the user for a date to enter in my program. So should I use scanf or should I store the date in a string and then use sscanf. I have to check for valid input for everything like day, month, year etc. I did it as below..
Code:
int assignments;
assignments = scanf("%d / %d / %d", &month, &day, &year);
fflush(stdin);
if (assignments != 3)
{
printf("Retry: ");
}
else
error checking.
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Aug 1, 2013
Code:
#include <stdio.h>
int main(void){
int a=0;
for(;a<=10;)
int b;
return 0;
}
I have got a code like this. I don't expect to get an output but just assumed I would see the command screen until I terminated it. What I want to do is just declare a variable b in a endless loop. But what I got from the compiler is this error: error: expected expression before 'int'. I am using Code::Blocks and I think the compiler is GCC.
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Jun 13, 2014
I'm using some rather large external libraries, and I want to load them in my .cpp file only. so, my header looks like this:
namespace {
// hidden declarations
namespace geometry {
class Point;
class Polygon;
class Box;
//etc
}
}
In the declaration of the main class in that header, I merely use these as pointers or references. The .cpp file looks as follows:
// Boost
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>
[Code] .....
This doesn't work however:
error C2371: '`anonymous-namespace'::geometry::Point' : redefinition; different basic types
1> e:..........NavigationMesh.h(10) : see declaration of '`anonymous-namespace'::geometry::Point'
What can I do to forward declare external classes like this?
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Jun 30, 2014
We have been assigned to create an iTunes library. Everything compiles in my other .h file but my main is not happy with my object declaration. It keeps stating "primary expression before '{'". Here is my main code:
#include<iostream>
#include<string>
#include<fstream>
#include"myTunes.h"
using namespace std;
//function protocols
void read(string);
[Code] ......
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Mar 18, 2013
I'm writing this program that basically interprets the rottentomatoes website. I am however having a problem declaring if it is rotten or fresh according to the rating the user enters.
I'm outputting it here:
void PrintAll(const string titles[], const int ratings[], int count) {
WriteLine('=', 50);
cout << "PRINT ALL" << endl;
WriteLine('-', 50);
[Code] .....
And here is my condition:
string RatingToString(const int ratings[], int count) {
string rank;
for(int i = 0; i < count; i++) {
[Code]....
Here is the output:
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950
==================================================
MENU
1. Add Movie
2. Print All
3. Exit
--------------------------------------------------
Enter 1-3 : 1
Title : Hitch
Rating : 90
==================================================
[Code]....
My condition works when there is only one movie, but when I add more, it gives it the new movies "ROTTEN" or "FRESH" rank.
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Sep 26, 2014
Is it permissible to declare, for example, `std::valarray<int&>`? If so, how do I initialize such if the `valarray` is a class member?
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Oct 29, 2013
I have the following code:
struct mystruct {
char fieldA[5];
char fieldB[7];
};
void dosomething(struct mystruct* pms) {
[Code] ....
Is there any problem doing that, even for a C89/90 compiler?
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Sep 9, 2014
see these sample:
Code:
#include <iostream>
#include <string>
using namespace std;
class test{
public:
virtual void ola() {
[Code] .....
Like you see, i don't re-declare the 'ola' function in 'test1' class, only in 'test' class. The compiler tell me the 'ola' isn't member of 'test1'. in 'test' i put it 'virtual', but forgetting that, how can i override it without re-declare it?
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