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Topic: Address of a function? (Read 5092 times) previous topic - next topic

franksmicro

Jan 22, 2011, 11:53 pm Last Edit: Jan 22, 2011, 11:54 pm by franksmicro Reason: 1
I was playing around seeing where the Arduino stores things in memory .  I used the following program:
Code: [Select]

int a;
int b=5;

void setup()
{
 int c = 6;
 int d = 7;
 unsigned long val;
 
 
 Serial.begin(9600);
 val = (unsigned long) &a;
 Serial.print("Address of a is "); Serial.println(val,HEX);
 val = (unsigned long) &b;
 Serial.print("Address of b is "); Serial.println(val,HEX);
 val = (unsigned long) &c;
 Serial.print("Address of c is "); Serial.println(val,HEX);
 val = (unsigned long) &d;
 Serial.print("Address of d is "); Serial.println(val,HEX);
 val = (unsigned long) setup;
 Serial.print("Address of setup is "); Serial.println(val,HEX);
 val = (unsigned long) loop;
 Serial.print("Address of loop is "); Serial.println(val,HEX);
 val = (unsigned long) &foo;
 Serial.print("Address of foo is "); Serial.println(val,HEX);
 val = (unsigned long) *foo2;
 Serial.print("Address of foo2 is "); Serial.println(val,HEX);
}

void loop()
{
 delay(1);
}

void foo()
{
 int i;
 Serial.println("Test");
 for(i = 0; i < 100; i++)
   Serial.println(i,DEC);
}

void foo2()
{
 Serial.println("Test");
}


This code produces (on ATMEGA328) the following output:
Code: [Select]

Address of a is 1AE
Address of b is 199
Address of c is 8F4
Address of d is 8F6
Address of setup is 85
Address of loop is 7E
Address of foo is 66
Address of foo2 is 5F


My question is - what do the addresses of foo and foo2 represent?  These functions are in ROM, not RAM, and I confirmed by disassembling the elf file the Arduino compiler creates in its working directory that the ROM address does not correspond to these values.  And I get the same value regardless if I use &func, func, or *func.

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