CODEWITHSUNDEEP
c++scopenamespaceslogicglobal-variables
Dan
Dan

Reputation: 29

Alternatives To Global Variables in C++

I need to set a variable in the main function and access it from a different function in the same file. I can not pass it to the function because it means changing the entire code structure, which is not an option. To avoid declaring a global variable I crated a namespace and I want to check if this is a good programming practice or is there a cleaner way to do it. This is the code:

namespace mylocalnamespace{
    int myglobalvar;
}

static void myFunc()
{
    ..... some code
    operationX(mylocalnamespace::myglobalvar);
    ..... some code

}
int main(int argc, char **argv)
{
   ..... some code
   mylocalnamespace::myglobalvar = atoi(argv[0]);
   ..... some code
}

Upvotes: 1

Views: 1025

Answers (1)

eerorika
eerorika

Reputation: 238321

Alternatives To Global Variables in C++

In the example, function argument is a good alternative to avoid a global variable:

static void myFunc(int mylocalvar)
{
    ..... some code
    operationX(mylocalvar);
    ..... some code

}
int main(int argc, char **argv)
{
   ..... some code
   mylocalvar = atoi(argv[0]);
   ..... some code
   myFunc(mylocalvar);
}

I can not pass it to the function

Oh well, then you have to use a global variable.

Since you apparently use it in a function with internal linkage, you could improve slightly by using global with internal linkage as well. This way the global won't leak to other translation units. A handy way to achieve that is an anonymous namespace:

namespace {
    int myglobalvar;

    void myFunc() {
        // ...

To avoid declaring a global variable I crated a namespace

Global variables are still global variables even if not in the global namespace.

Upvotes: 2

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