Is passing pointer argument, pass by value in C++?

Is passing pointer argument, pass by value in C++? Since i see that any change to the pointer as such is not reflected outside the method. The changes i do by dereferencing the pointer is reflected though.

In that case, is it acceptable/standard procedure to use pointer to pointer as argument to a function to modify the pointer value as such within a function?

Is passing pointer argument, pass by value in C++?, Passing by value is the most straightforward way to pass parameters. When a function is invoked, the arguments are copied to the local scope� Example: Passing Pointer to a Function in C Programming. In this example, we are passing a pointer to a function. When we pass a pointer as an argument instead of a variable then the address of the variable is passed instead of the value. So any change made by the function using the pointer is permanently made at the address of passed variable

I understand the confusion here. The concepts of "pass by value" and "pass by reference" are not so clear even if they seem to be so. Bear in mind that the computer does not know these concepts and does not behave according to it. The computer does not know about the types. Hence it does not make a distinction of pointers and values. Let me try to explain by and example:

void func1(int x)
{
   x = 5;
}

void func2(int *x)
{
   int a;
   x = &a;
}

The operation is same for the machine in both functions: It gets the argument and changes it. Note that, in second function it does not modifiy *x, it modifies x.

Now if we call these functions,

int y = 10;

func1(y); //value of y does not change

func2(&y); //value of &y does not change, but the value of the address which y points may change. 

I prefer to say that, basically, every function call is "call by value". But in the case of a pointer type, we have a way to change the content of another address in memory.

If we had written func2 as

void func2(int *x)
{ 
   *x = 5; 
}

Then, this would be a real case of "call by reference".

C++ Pass by Value, Pointer*, &Reference | by Kevin Yang, Passing pointers to functions in C - C programming allows passing a pointer to a function. To do so, simply declare the function parameter as a pointer type. we pass an unsigned long pointer to a function and change the value inside the� C programming allows passing a pointer to a function. To do so, simply declare the function parameter as a pointer type. Following is a simple example where we pass an unsigned long pointer to a function and change the value inside the function which reflects back in the calling function

Pass by value using Pointers I'll explain it by example:

void f(int *ptr)
{
   cout<<*ptr;
}


int main ()
{
   int a=10;
   int *aptr=&a;
   f(aptr);
   return 0;
} 

Here, in main function a is an integer variable whose content is 10 and address is 00F8FB04 (assume). aptr is pointer to integer, that store the address of integer variable a, so aptr content is address of integer variable a that is 00F8FB04. When we pass aptr as the function argument only content of aptr (that is address) are copies to function parameter. So, ptr will receive the copy of content of aptr (that is address 00F8FB04)

Passing pointers to functions in C, The arguments passed in and worked with inside the function are dereferenced pointers, which, from the programmer's perspective, is essentially� » Call by Value (Pass by value) » Call by Pointer (Pass by address) » Call by Reference (Pass by Reference) C++ supports all these three types of passing values to the function, whereas C Supports the first two types only. The argument used to send values to function are known as input arguments.

Either a pointer to a pointer, or a reference to a pointer, is what you would use if you wanted to potentially change the pointer itself. To your original question, technically, yes, all parameters are passed by value.

Passing by value, passing by reference in C - DEV, In C++, we can pass parameters to a function either by pointers or by reference. In both the cases, we get the same result. So the following questions are� Passing vector to a function in C++; Passing NULL to printf in C; Parameter Passing Techniques in C/C++; Passing and Returning Objects in C++; How to delete an element from the Set by passing its value in C++; When do we pass arguments by reference or pointer? Different ways to use Const with Reference to a Pointer in C++; Reference to a

Yes it is, as it is in C.

In that case, is it acceptable/standard procedure to use pointer to pointer as argument to a function to modify the pointer value as such within a function?

In which case? What do you want? You can use real references with the & modifier.

void func(type &ref);

Passing by pointer Vs Passing by Reference in C++, If a pointer is passed to a function as a parameter and tried to be modified then the changes made to the pointer does not reflects back outside that function. This is� One of the uses of pointer variables in C++ is in passing arguments to functions. To understand why this is important, you need to understand how arguments are passed to a function. Passing by value in C++ By default, arguments are passed to functions by value. This has the somewhat surprising result that changing the …

Passing Reference to a Pointer in C++, As you can see, the function foo() changed the value of the argument (variable value) through pointer parameter ptr. Pass by address is typically used with pointers� Passing argument to a function by value is also know as call by value. this method of passing arguments to a function copies the original value of argument into the formal parameter of a function. in other words if we change parameter which are given inside a function posses no effect on the argument . c language support by default call by value for passing arguments. below is the example of

7.4 — Passing arguments by address, That means, both the passed variable and the parameter used in the called function point to the same location and are always� This is the benefit of passing the arguments by value. However, when the arguments are passed on by pointers, the actual parameters are passed on to the function. The function gets the values from the actual addresses of the parameters. Any change in the values of arguments by the function gets stored at the addresses of parameters.

Passing by Reference vs Passing by Pointer in C++, We've seen Pass By Value and Pass By Reference. If you declare a formal parameter of a function as a pointer type, you are passing that parameter by its� If a pointer is passed to a function as a parameter and tried to be modified then the changes made to the pointer does not reflects back outside that function. This is because only a copy of the pointer is passed to the function. It can be said that “pass by pointer” is passing a pointer by value. In most cases, this does not present a problem.

Comments
  • The pointer is passed by value but the object pointed-to by the pointer can be modified by the function (const-qualification depending).
  • @Arafangion: I edited my answer to explain why preferences should be preferred to pointers.
  • I suppose it's subjective - I prefer using references because I move the responsibility for null pointer checking to the caller, and I usually don't care about C compatibility. However I'm not sure I'm sold on "You also need function prototypes to be sure that the value is not changed" - that's true for many of C++'s classes - they could be pointers themselves and might or might not be sharing data. That said, I do prefer pass by value and letting the class take care of any pointers if any are needed, unless I'm returning rvalue references that should be immediately set, regardless, +1
  • @Arafangion: the pointer validity checking place in C is also a matter of calling convention. I usually perform it at caller level for inner functions and check at malloc or external entry points for lib. But indeed with reference, checking a variable is not NULL sounds and looks dumb. But it is also not less dumb when using C when you pass the address of some automatic array and the first thing done by callee code is just checking it's not NULL.
  • "All parameters are passed by value" No, arguments passed by reference are not passed by value.