avr-gcc, avr-libc compiler and toolchain known bugs

[WestfW]

This "issues" is supposed to collect "known" problems with tool versions that are not actually in use. So it's not so much a bug to be fixed as a warning sign for experimenters.

The Arduino environment, as of version 1.0.2, uses avr-gcc version 4.3.2, binutils 2.19, and avr-libc 1.6.4 These are pretty old. But several more recent versions have serious bugs when one attempts to use them with Arduino.

1. Global Constructor bug.
   This is the bug that infamously caused any Arduino MEGA sketches to fail at runtime in large sketches when compiled under linux with the 4.5.3 release.
   Arduino issue http://code.google.com/p/arduino/issues/detail?id=131
   This is avr-gcc bug: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45263
   It broke in 4.4.something, is known broken in 4.5.3 and 4.6.0, and known fixed in 4.5.4, 4.6.1, and 4.7.0

2. "round()" incompatibility
   http://code.google.com/p/arduino/issues/detail?id=604

3. byte assembly (shift) bug
   (broken in 4.4.0, 4.5.3, 4.6.1. Fixed in 4.5.4, 4.6.2, 4.7.0)
   http://code.google.com/p/arduino/issues/detail?id=605
   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51445
   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46779

4. delay() bug introduced with binutils 2.21.1
   http://code.google.com/p/arduino/issues/detail?id=689

5. util/delay.h bug wrt math.h
   https://savannah.nongnu.org/bugs/?34047

6. progmem is used wrong, nearly everywhere. Mostly this breaks g++
   (avr-gcc 4.7.2 apparently significantly changes the way progmem is handled?)
   http://savannah.nongnu.org/bugs/?33716
   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38342

I'll add more when and if I find or remember them...

[amcjen]

Thanks Bill for posting these. This really helps to understand what is actually broken where. Appreciate you putting these up.

[ffissore]

Fixed. See #611