Global variable goes out of scope.

Fermat · #1 16-Apr-2007, 16:30

I know how to use global variables across different files - with the extern keyword etc.

My problem is with a global variable going out of scope in its own file.
I declared three global variables at the top of the file, outside of any functions.
I had a vector of strings, v1. An array of ints, num[], and an int variable, number.

The vector v1, the array num[] and the variable number, are three global variables within the one file, test_the_code.cpp.
The vector v1 can't be assigned values with push_back() within the function test_code(). When I do that, then during debug, if I try to get the debugger to give the value of the vector elements, I get told "variable is out of scope". A few minutes/moments later, the IDE crashes. It's as if the debugger is trying to read an infinte amount of data - as if there were no end to the number of elements in the vector.

The array num[] can't be assigned values within the function test_code(). Just before the assignment, num[0] = 1, during debug, the array has "random" values for its elements. (It doesn't even keep its globally assigned element values.) After the assignments, the values are unchanged - still "random".
The assignment n1 = num[0] doesn't seem to work either. Although uninitialised, n1 had a value of zero. After the assignment, its value was 1. It wasn't even the random value the debugger gave for the value of num[0].

Only the global variable, number, works.
Inside the function test_code(), it keeps its globally assigned value of 100. When I assign a value of 99 to it, it takes that value.

Conclusion: global vectors and arrays go out of scope within a function in the same file, but ordinary variables don't.

Any ideas, suggestions, hints ??

I can get global variables to work ok in an ordinary console app, but not in a windows app. Why not ??

Here is my code - from the windows app. Using Visual C++ 2005.
I created a windows app with a single form. I put a buttton on that form. When I run/debug the app, and I click on the button, it takes me to a button-click() function that calls my test_code() function.
I have edited the code a bit a to save space, since a lot of it is just initialisation of windows components.
The only relevant code in Form1.h is the button_click() function at the end. Its name is Testerbtn_Click().

All other code not included is just a mass of files created by the IDE when I created the windows app. None of that code has been altered

Quote:

//Form1.h

#pragma once

void test_code(void);

namespace TesterProject {

using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;

public ref class Form1 : public System::Windows::Forms::Form
{
public:
Form1(void)
{
InitializeComponent();

}

protected:
~Form1()
{
if (components)
{
delete components;
}
}
private: System::Windows::Forms::Button^ Testerbtn;
protected:

private:

#pragma region Windows Form Designer generated code
void InitializeComponent(void)
{
// code to initialise windows components
}
#pragma endregion
private: System::Void Testerbtn_Click(System::Object^ sender, System::EventArgs^ e)
{
test_code();
}
};
}

CPP / C++ / C Code:

//test_the code.cpp

#include <iostream>
#include <string>
#include <vector>

using namespace std;

vector<string> v1;
int num[4]={9,8,7,6};
int number = 100;

void test_code()
{
	v1.push_back("1");
	v1.push_back("2");

	num[0]=1;
	num[1]=2;
	int n1 = num[0];

	number = 99;
}
// end test_code

Fermat · #2 16-Apr-2007, 20:41

It's a debugger/IDE problem.

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Global variable goes out of scope.

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