const vs non const definition

Forum 2005-2010 (read only) Software Syntax & Programs
1

Hi,
i am doing a menu driven interface and just come to a issue,
i wish to put the declaration of the menu in a const instead, so it won't use as much ram (i hope that the compiler put that in the flash)

const char* Menu1[] = {" 1.DMX Channel      ", 
                 " 2.Fixture          ", 
                 " 3.Scene            ",
                 " 4.Step             ",
                 " 5.Setup            ", 
                 " 6.Another Menu     "}

but as soon as i try to pass that in a function, it won't work anymore?

void loop()
{
 Choix=ScrollMenu((Menu1, EncPulse);
 }

This is the scrollMenu declaration

int ScrollMenu(char *Menu[], int Direction)
{

i don't get it? should const be exactly the same as normal var?
This is the error i get
error: invalid conversion from 'const char**' to 'char**
if i remove the 'const' it works but i got so many menu that i don't want to eat the whole ram!
Thanks in advance guys
Patgadget
Montreal

2

The function prototype for 'ScrollMenu' is expecting a non-const pointer, so you get an error message. In theory, the difference could affect optimisations. You could try casting the const pointer to just plain 'char *', or (if you have the source to 'ScrollMenu'), change the prototype.

3

Thanks
casting it to const fix it

int ScrollMenu(const char *Menu[], int Direction)

what about the 'const' declaration? are they in flash or ram?
Thanks again
Patgadget
Montreal

4

"what about the 'const' declaration? are they in flash or ram?"

Unless you specify progmem they are kept in both.