PROGMEM and struct/class members

i put class in program space , able access members having difficulty doing in simplest of examples. here code:

code: [select]


// fun with progmem

#include <avr/pgmspace.h>

#define line {serial.print(l++);serial.print(" ");}
typedef unsigned const int prog_uint16_t;

int iram=11;
struct a {
public:
  prog_uint16_t    a;
  a():a(33){};
  prog_uint16_t * getaaddr() const { return &a; }
};

progmem  prog_uint16_t iflash=22;

a const progmem a;


void setup() {
  int l=1;
  serial.begin(115200);
  delay(2000); //alow time open serial console
  
  line; serial.print(f("single  int/ram value    ")); serial.println(iram);
  line; serial.print(f("single  int/ram address  ")); serial.println((int)&iram);
  serial.println("");
  line; serial.print(f("single  int/progmem value/ram   ")); serial.println(iflash);
  line; serial.print(f("single  int/progmem address     ")); serial.println((int)&iflash);
  line; serial.print(f("single  int/progmem value/flash ")); serial.println(pgm_read_word(&iflash));
  serial.println("");
  line; serial.print(f("class  int/progmem value/ram   ")); serial.println(a.a);
  line; serial.print(f("class  int/progmem address     ")); serial.println((int)&a.a);
  line; serial.print(f("class  int/progmem address     ")); serial.println((int)a.getaaddr());
  line; serial.print(f("class  int/progmem value/flash ")); serial.println(pgm_read_word(&a.a));
  line; serial.print(f("class  int/progmem value/flash ")); serial.println(pgm_read_word(a.getaaddr()));

}

void loop() {

}



and produces following output:

code: [select]

1 single  int/ram value    11
2 single  int/ram address  256

3 single  int/progmem value/ram   22
4 single  int/progmem address     415
5 single  int/progmem value/flash 22

6 class  int/progmem value/ram   17967
7 class  int/progmem address     417
8 class  int/progmem address     417
9 class  int/progmem value/flash 0
10 class  int/progmem value/flash 0


line 3 looks unusual, i'm supposing small enough programs, flash locations accessible using instructions read ram. (i see similar result in line 6 of eliminate print() statements.)

lines 9 , 10 ones trouble me. cannot seem retrieve value of member of flash. searched forum discussions on , there several showed how put objects flash found none demonstrated how retrieve them.

this built using 1.5.8 ide 1.0.6 ide produces following error (after clean complaints relating typedef):

code: [select]

progmem:18: error: causes section type conflict

any on retrieving member variables flash appreciated! first real project , i've exceeded ram capacity!

i don't understand why want this.

text or tables data can created in progmem. big in class want in progmem ?

what else have in ram ?
if need many buffers ethernet , sd card , pixel display , many more, going need arduino mega 2560 someday anyway.

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