[avr-gcc-list] array of pointers to functions - ok in RAM, fails in flash

[David McNab]

Hi,

I'm creating a table of pointers to functions, where each function is
like:
    void func(void) { ... }

When I place the table into RAM, I can access elements, and dereference
those elements to execute the corresponding functions. This works fine.

For example:

    void (*func_tab[])() = {
        func1, func2, ...
    };

    void main () {
        void (*funcptr)(void);
        ...
        funcptr = func_tab[1];
        (*funcptr)();
        ...
    }

But when I place the table into flash instead, my program goes off into
the boonies when I try to invoke the function:

    #include <avr/pgmspace.h>

    void (*func_tab[])() = {
        func1, func2, ...
    };

    void (*func_tab_flash[])() PROGMEM = {
        func1, func2, ...
    };

    void main () {
        void (*funcptr)(void);
        ...

        funcptr = func_tab[1];        // the variable holds 0x90
        (*funcptr)();                 // this works just fine

        funcptr = func_tab_flash[1];  // the variable holds 0
        (*funcptr)();                 // this sends us into the boonies
    }

Surely it can't be too hard to place a table of function pointers into
flash, retrieve function pointers from this table, and 'call' them.

What am I doing wrong? Otherwise, what workarounds are available?

Cheers
David