Elysian Shadows

ismetteren wrote:My guess is that they are declared on the stack and get deleted when they go out of scope.

Scoody wrote:Since you're just passing a pointer to the string, only the pointer gets removed when the function ends.

void function(char* string);
void function(char string[]);

optLog wrote:

Scoody wrote:Since you're just passing a pointer to the string, only the pointer gets removed when the function ends.

So if you didn't deallocate the memory or reference it then it would be leaked right?
also:
would these two functions act the same way?

Code: Select all

void function(char* string);
void function(char string[]);

void StringFunction(char *string);

int main() {
    char string[100]; //allocated on the STACK
    StringFunction(string); //passing memory address to first element
    //string is removed from the stack implicitly when the program exits.
    return 0;
}

 int main() {
    char *string = malloc(sizeof(char)*10); //allocate the array dynamically on the heap
    StringFunction(string); //still passing the memory address, it makes absolutely no difference.
    free(string); //You are responsible for deleting dynamic memory now.
    return 0;
}

would these two functions act the same way?

Code: Select all

void function(char* string);
void function(char string[]);

char string[100];
char *charPointer;

charPointer = string;
charPointer[0] = 'h';
charPointer[1] = 'e';
//etc.

optLog wrote: When I ran the program it crashed which leads me to believe that "this is a string" is allocated as part of the main function or something because if a copy of "this is a string" was being passed to the function I can't think of a reason why changing one of it's values would cause the program to crash.

dandymcgee wrote:

optLog wrote: When I ran the program it crashed which leads me to believe that "this is a string" is allocated as part of the main function or something because if a copy of "this is a string" was being passed to the function I can't think of a reason why changing one of it's values would cause the program to crash.

It is passed as a const char array. You cannot edit constants at run-time.

avansc wrote:(stuff)

Correct, but it also only has scope for that function. and yes, its on the stack. (if memory serves me correctly);

eatcomics wrote:

avansc wrote:(stuff)

Correct, but it also only has scope for that function. and yes, its on the stack. (if memory serves me correctly);

Ha... stack, memory, good one

optLog wrote:let me rephrase my first question a little bit.

Code: Select all

void someFunction(char* string);
int main()
{
  someFunction("this is a string");
  return 0;
}

how is the string literal "this is a string" handled in memory?
Is it allocated as part of the main function or is memory dynamically allocated for it when the main function calls someFunction?
Is the same copy of "this is a string" sent to someFunction or is a copy of it made and sent to someFunction?

optLog wrote:I'm sorry everyone I guess I've been asking the wrong question. what I'm trying to find out is how literals are stored in memory.

Ginto8 wrote:

optLog wrote:I'm sorry everyone I guess I've been asking the wrong question. what I'm trying to find out is how literals are stored in memory.

IIRC they're usually stored on the stack. Sometimes the compiler may optimize it differently, but that is (I think) the general case. There is no need to worry about memory management with constant literals.