Arduino ports registers in Eclipse are not working - c++

Question

I am building a Arduino application in C with Eclipse and the Arduino plugin. In my old code I used pinMode and digitalWrite. But as you all know, this uses more space. So I am re-building my code now with port manipulation. If you don't know what that is, you can see it here: http://www.arduino.cc/en/Reference/PortManipulation
I will explain what I did.
Where there stands pinMode, I changed it to something like this: DDRD = 0b11111111;
And where there stands digitalWrite, I changed it to PORTD = 0b10000000;
You can see it in my code below.
Eclipse is now giving me the error (highlighting the words DDRD and PORTD with a red line) of symbol not resolved for DDRD and PORTD, but the program is building and running normal. How do I solve this?
#include <avr/io.h>
#include <util/delay.h>
int main()
{
UCSR0B = 0; // disconnect pins 0 and 1 from USART (Serial)
DDRD = 0b11111111; // all pins of port D as output
for(;;)
{
PORTD = 0b10000000; // Pin 7 on
_delay_ms(500); // Wait
}
}

Answer 1

These are multi-level macros which encode direct volatile access to the SFR locations.
They are individually defined in one of an assortment of chip-specific header files which avr/io.h will include when it is informed of the specific CPU variant you are using.
Normally this is done with the -mmcu flag to avr-gcc, for example
-mmcu=atmega328p
However, if the Eclipse plugin does it's own pass through the project sources to try to give you advisory errors, it may not be smart enough to turn that into a define (you can get Eclipse claiming errors even when gcc is happy). To work around that, you may need to explicitly define the cpu type above the include in your code, or in some configuration for Eclipse. For example:
#ifndef __AVR_ATmega328P__
#define __AVR_ATmega328P__
#endif
#include <avr/io.h>
Note that this may cause problems if you later change the processor type! And even as is, it's a little iffy as there are two potential names for each processor.

Answer 2

I have faced the same problem. This is what solved for me in Eclipse.
From project explorer right click on the active project > Index > Rebuild