Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 1. Using the compiler

Select Project>Options. In the General Options category, click the Heap 
configuration page. 

Add the required heap size in the appropriate text box.

The size of the heap segments are defined in the linker command file. 

The default linker file sets up a constant, representing the size of each heap, at the 
beginning of the linker command file:

-D_TINY_HEAP_SIZE=size

-D_NEAR_HEAP_SIZE=size

-D_FAR_HEAP_SIZE=size

-D_HUGE_HEAP_SIZE=size

-D_HEAP_SIZE=size /* For CLIB */

Specify the appropriate size for your application.

If your application uses near or far memory, symbols for heaps for these memories 
should also be defined in the linker command file.

The actual heap segment is allocated in the memory area available for the heap:

-Z(DATA)HEAP+_TINY_HEAP_SIZE=60-25F

Note: This range does not specify the size of the heap; it specifies the range of the 
available memory.

Use the same method for all used heaps.

If you have excluded 

FILE

 descriptors from the DLIB runtime environment, like in the 

normal configuration, there are no input and output buffers at all. Otherwise, like in the 
full configuration, be aware that the size of the input and output buffers is set to 512 
bytes in the 

stdio

 library header file. If the heap is too small, I/O will not be buffered, 

which is considerably slower than when I/O is buffered. If you execute the application 
using the simulator driver of the IAR C-SPY Debugger, you are not likely to notice the 
speed penalty, but it is quite noticeable when the application runs on an AVR 
microcontroller. If you use the standard I/O library, you should set the heap size to a 
value which accommodates the needs of the standard I/O buffer.