I've simplified things slightly - but the basic point is that both functions are in the same source file and they both have a static std::string called 'x'. Being static, I guess they aren't (strictly) local variables. So how does the compiler know that they're different entities? Does it encode their signatures using the function name or something like that? If I call each function separately I do seem to get the correct string...
Is it possible to use & change global variables in a Static Library? For example:
I declare a bool test = true; globally.
Then later in an exported function If the user wants, he can set that test to false. So the program later when checks test if it's true, will notice that it's not true, since one of my function changed it.
I see many time where static data member is used to count creations of objects -
i.e.
1. the static data member is init to 0
2. the static data member is incremented by 1, in the Class' constructor, every time an object is created
However, if you define a global object of a class,
How can you tell that the static data member is initialized BEFORE the constructor of the global object is called? (i.e. before the global object is created).
Because to my understanding, you do not know in advance the order of global objects' creation -
so the Global Object could be created BEFORE the static data member was created and initialized.
//Declare Variables String lstNme, frstNme, finalGrade; Double pointsEarned, percentage; //Get First Name, Last Name and Score
[Code]....
I am getting the error popping up on the line 58 under the console.writeline...+finalGrade "Error1Use of unassigned local variable 'FinalGrade' The thing i am not understanding is that it is declared
I have made an application and I have basically solved everything. But the only problem is that I am using global variables because it felt like the smoothest, so my program is built on it.
But now I've read around and I understand that you should not use these(?). Do you think pointers is the best think to use instead?I have previously declared my board array and some variables as global and I want them in alot of functions.I have read and understand the procedure for the use of pointers so I can use my int's in the other functions by doing like this? Code: #include <stdio.h>
int justprint(); int main() { int Row = 2; int Column = 2; int *pRow = &Row; int *pColumn = &Column; [code]...
But how do I do it with an array like this one? If I declare it in the main function, and then want to use it in other functions.Or are there better, easier solutions?
On linux, I can compile DLLs (shared objects) as well as executables that use them. I can even access globals and classes that are defined in the EXE from the DLL, and vice versa, simply with the 'export' keyword. flawlessly.
The Problem: But on Windows (using MinGW), no matter what I do, I'm completely unable to access global variables which defined in the EXE, from the DLL. On Linux, this is no sweat, but what's Windows' problem?
I also need to extend classes in the dll with base class method definitions defined in the exe.
Ive heard that on Windows, you need to use declspec(dllimport) and declspec(dllexport). I can compile with CygWin+MinGW/g++4.5.3 as well as "Pure Windows" with MinGW/g++4.7.2 *without* the declspecs. So what's the decljunk for? Is this really just something for MSVC or other compilers?
Here's some Windows code to show what the problem is. The DLL's global variable is accessible to the EXE just fine, but the EXE's global variable is not accessible to the DLL - compilation complains it is an undefined reference.
main.cpp #include "myLib.h" #include <stdio.h> int exe;
[Code].....
edit: I tried using --enable-runtime-pseudo-reloc --allow-shlib-undefined options when compiling the DLL and G++ complains that --allow-shlib-undefined is an unrecognized option.
I am using VS2010 to develop an app which includes several windows forms that I am trying to set up global variables for, and I am getting a few errors like:
LNK2005: "wchar_t *dsn"...already defined in ....obj
I have a header file (externals.h) with: #ifndef MY_GLOBALS_H #define MY_GLOBALS_H extern long dbg; extern wchar_t dsn[50]; extern wchar_t u[30]; extern wchar_t p[30]; #endif
and 2 different forms, each with different namespaces, but both including the above header (#include "externals.h").One of the form .h files defines the values for these externally declared variables like this: namespace PWValidationTools{
public ref class ValidationSetupForm : public System::Windows::Forms::Form { }
The other form file only uses these variables, never defines them.I am getting the above LNK2005 error only for the variables declared as wchar_t, not the "long" one. why I'm getting the link errors only for the wchar_t variables.
I have the following code. According to this the values of pointers p[0] and p[1] remains unchanged since the swap is made to local variables in swap function.Now my doubt is how can I swap the pointers p[0] and p[1] inside the function swap??
I am trying to get variables that are global to multiple files. I have mananged to make constant variables that are global but maybe not in the best way. In the header i have the constant variables being defined:
const int variable_Name = 5;
And the cpp file:
#include <iostream> using namespace std; #include "vars.h" int main ( ) { cout << variable_Name<< endl; system ("pause"); return 0; }
Is there a better way to do this and to make the variables able to be changed within the cpp files.
I realize that implicit int rule was removed in C99 but gcc still takes this approach by default. I wonder why this happens:
bbb = 5; // legal int main(void) { aaa = 10; // illegal auto aaa = 10 // legal
Inside function a specifier is needed. Error message with no specifier used is:
error: ‘aaa’ undeclared (first use in this function)
Is this because of linkage - bbb variable has an external linkage so compiler knows that we are defining a variable here while inside mean() we need to show compiler that aaa is defined right here, it does not come from external functions?
I need to transform a local variable into a global variable so I can use it in one of my functions. I thought about passing the value as a parameter to this function but I can do this since the function is called inside the while loop and this variable counts how many times the while loop does (so the final value is outside the loop). Example to visualize better:
I am trying to compile a c program for sudoku. I have declare const instances as global variables, but when i try to compile the code it says that my declarations are not constant, here is some of the code.
#include <stdio.h> #include <assert.h>
const int GRIDSIZE = 3; const int GRID_SQUARED = GRIDSIZE * GRIDSIZE; //this line const int ALL_VALUES = (1<<GRID_SQUARED)-1; //and this give//the error int board [GRID_SQUARED][GRID_SQUARED];
If I have a static variable in a class e.g. a pointer to another class like this: (B is another class)
class A { public: static B* cB; };
Then I set that variable and create multiple instances of class A like this:
A::cB = new B; As = new A[Number];
Then will the value of cB be the same across all instances?
I cannot pass the class pointer in the constructor as I need to create an array of instances. I tried this method but I get linker error.... unresolved external.
Is it more expensive to use too many static variables instead of ordinary variables? If yes, then how?------------This is a topic given to me to find out about and I don't even know what are static variable except that they live throughout the life of program
and only disadvantage of using static variable instead ordinary variables in my mind is just they will use memory even when we don't need them
Can local variable be passed as the parameter for a new created thread procedure? Here is the example code:
Code: void CDLG::some_function() { CString strFileName="abc.doc"; //local variable, can it be valid for being passed into the following new thread??? //Can strFileName still be accessed from within the stack of thread procedure? ::AfxBeginThread(ProcessContentThread,(LPVOID)&strFileName); }
[Code]...
There is another method using variable on the heap,
I test these code, both methods work as expected, but I doubt whether the first method is a good way. OR if only the second method is the correct way to pass a parameter to a thread.
