Is it possible to release the memory used by C strings when done using them?

Projects Programming
1

Let's assume that I create a C string like this:

char MyVar[] = "This is string of characters that I only need temporarily in my project]";

After I am done using this and no longer need it in my project, is there any way to free up the space that this string was using?

2

Where is it created?
Is it a global, or is it a local variable?
If it’s a local variable, then it’s on the stack. It automatically gets freed when your function ends.
If it’s a global, then it’s a statically allocated and can’t be freed.

You can leave it in flash using PROGMEM and access it from there. Or use F(“”) if you are using it in Serial.print. Depends how you are using it.

Edit: If you what dynamically allocated and freed strings, use String class. But as you probably know that has its own problems of memory fragmentation. You won’t solve that just by moving to char[] instead, except by use of the stack.

Give a complete example sketch if you want a complete answer of how to free up RAM. Otherwise this question is just too vague to give a definitive answer.

3

I hope that the delete function works with Arduino also as it works in c++.try

delete MyVar;

I hope it might work. This function delete the memory of the variable

4

m_k_akash:
I hope that the delete function works with Arduino also as it works in c++.try

delete MyVar;

I hope it might work. This function delete the memory of the variable

Only on objects that were created with new function.

5

hsehestedt:
After I am done using this and no longer need it in my project, is there any way to free up the space that this string was using?

In the small memory of an Arduino the real question IMHO is "what are you going to do with the memory after it is freed up" - I reckon that is where the problems will arise.

As mentioned by @pcbbc if you use the F macro the string won't use any SRAM in the first place.

...R

6

pcbbc:
Where is it created?
Is it a global, or is it a local variable?
If it’s a local variable, then it’s on the stack. It automatically gets freed when your function ends.
If it’s a global, then it’s a statically allocated and can’t be freed.

Thanks, that's exactly what I needed.

7

You can't free the memory from a const, global or static string, but you can re-use the string for another purpose, provided you respect the allocated size.

Regards,
Ray L.