GCC doesn't seem to know the size of memory available about avr-gcc-build HOT 4 CLOSED

Reason is that Binutils works on emulation level, i.e. is knows -mavrxmega2 or -mavr51, and the layout of MEMORY regions comes from the emulation default. For example, the top of the default linker scripts read something like (here from avr51.x):

__TEXT_REGION_ORIGIN__ = DEFINED(__TEXT_REGION_ORIGIN__) ? __TEXT_REGION_ORIGIN__ : 0;
__TEXT_REGION_LENGTH__ = DEFINED(__TEXT_REGION_LENGTH__) ? __TEXT_REGION_LENGTH__ : 128K;
__DATA_REGION_ORIGIN__ = DEFINED(__DATA_REGION_ORIGIN__) ? __DATA_REGION_ORIGIN__ : 0x800100;
__DATA_REGION_LENGTH__ = DEFINED(__DATA_REGION_LENGTH__) ? __DATA_REGION_LENGTH__ : 0xff00;
...
MEMORY
{
  text   (rx)   : ORIGIN = __TEXT_REGION_ORIGIN__, LENGTH = __TEXT_REGION_LENGTH__
  data   (rw!x) : ORIGIN = __DATA_REGION_ORIGIN__, LENGTH = __DATA_REGION_LENGTH__
  ...
}

Hence, when symbols like __TEXT_REGION_LENGTH__ are not defined, the core specific defaults are used which are large enough so that all MCUs in that core family will fit.

A canonical place to define these symbols is in the startup code. Stock AVR-LibC currently does not define respective symbols, but there is avrdudes/avr-libc#936 to (weakly) define respective symbols.

crt*.o from atpacks has these symbols defined, so it makes a difference which crt you are using. See avr-nm crt*.o | grep REGION .

For the time being, you can define the symbols on the command line, e.g. -Wl,--defsym,__TEXT_REGION_LENGTH=64k or in the device-specs file, for example:

*link_text_start:
        --defsym __TEXT_REGION_LENGTH=64k

from avr-gcc-build.

Update: the issue goes away when using the Atmel DFP (-B ... flag)

from avr-gcc-build.

Did also run into this problem. The -B flag does not work for me. What flags exactly you use?

Furthermore the SysProgs compiler (only for Windows) works out of the box with correct region size. So somehow it must be possible to get the correct behavior also on Linux.

from avr-gcc-build.

@mobacon Did you pass the right argument to -B? I point it to the extracted DFP like this:

-B _deps/atmegadfp/gcc/dev/atmega640

from avr-gcc-build.