Hi (The URL for avr-gcc for Linux in my previous post was wrong but it isn't important ...)
Arduino seems to built avr-gcc with https://github.com/arduino/toolchain-avr It's opening page states: binutils-2.26 gcc-5.4.0 avr-libc-2.0.0 gdb-7.8 Not gcc-7.3.0 as released as 1.8.10 at https://www.arduino.cc/en/Main/Software as I see today. It seems to patch upstream a bit. Further check realized that, staging branch was using gcc-7.3.0 in code https://github.com/arduino/toolchain-avr/commit/3e30e20948a5e3445823ecef23c007937b36583e The applied patches are extensive!!! (Readme.md was not updated yet) So this is one key resource. Providing both avr-gcc 5.4.0 and 7.3.0 as patched by Arduino toolchain-avr main and staging branches with update-alternatives may be the best for next release. I also found https://gcc.gnu.org/gcc-10/changes.html#avr | Support for the XMEGA-like devices | | ATtiny202, ATtiny204, ATtiny402, ATtiny404, ATtiny406, | ATtiny804, ATtiny806, ATtiny807, ATtiny1604, ATtiny1606, | ATtiny1607, ATmega808, ATmega809, ATmega1608, ATmega1609, | ATmega3208, ATmega3209, ATmega4808, ATmega4809 | | has been added. | A new command line option -nodevicespecs has been added. It allows | to provide a custom device-specs file by means of | | avr-gcc -nodevicespecs -specs=my-spec-file <options> | | and without the need to provide options -B and -mmcu=. See AVR | command line options for details. This feature is also available in | v9.3+ and v8.4+. New command line options -mdouble=[32,64] and | -mlong-double=[32,64] have been added. They allow to chose the size | (in bits) of the double and long double types, respectively. Whether | or not the mentioned layouts are available, whether the options act | as a multilib option, and what is the default for either option is | controlled by the new AVR configure options --with-double= and | --with-long-double=. A new configure option --with-libf7= has been | added. It controls to which level avr-libgcc provides 64-bit | floating point support by means of Libf7. A new configure option | --with-double-comparison= has been added. It's unlikely you need to | set this option by hand. So gcc-10 had some AVR support efforts. Osamu
