Summary of changes in the 1.4 release line

The following list shortly summarizes the changes in version 1.4.0 compared to version 1.2.6 of AVR Libc, which was the latest release from the 1.2 release line by the time 1.4.0 was released.

Note that the purpose of the first four changes is to eventually get rid of the term signal alltogether in favor of the more common term interrupt (interrupt vector, interrupt service routine).

• The INTERRUPT() macro has been deprecated, and it will be removed in a future version. Use __attribute__((interrupt)) explicitly if this functionality is really needed.
• A new ISR() macro has been added, and is now the preferred form to introduce an interrupt service routine. It is equivalent to the old SIGNAL() macro, which might become deprecated in a future version.
• The last remaining parts from <avr/signal.h> have been moved to <avr/interrupt.h>, so the former header file is no longer needed, and has been deprecated.
• A new set of interrupt vector names has been added, where the base name itself is closely derived from Atmel's datasheets and XML files, with _vect appended. E.g. the former SIG_INTERRUPT0 now became INT0_vect. The old names are still available, but their use for new projects is discouraged.
• A new header file, <compat/deprecated.h> has been established. Its purpose is to collect deprecated items from older versions of the library, starting out with the enable_external_int(), timer_enable_int(), and INTERRUPT() macros/functions, as well as the old obsoleted inp/outp/sbi/cbi macros.
• The standard IO facilities API has been enhanced:
  • The backend functions put and get that are passed to fdevopen() during the setup of a stream now take the stream itself as an additional argument. By defining the macro __STDIO_FDEVOPEN_COMPAT_12 before including <stdio.h>, an fdevopen() function prototype will be declared that is backwards-compatible with avr-libc version 1.2 and before.
  • It is possible to tie user data to a stream using fdev_set_udata(), and to retrieve them using fdev_get_udata(). Together with the additional argument to the backend functions, these functions can now e.g. keep track of internal user state, or distinguish two different devices using the same backend function.
  • The get backend function can now return _FDEV_EOF to indicate an end-of-file condition, in addition to _FDEV_ERR for an error condition. This will affect the internal state that can be queried using the standard feof() and ferror() functions.
  • A new macro fdev_setup_stream() is provided to setup a user-supplied stream without the need to call fdevopen(), and thus without requiring malloc(). A similar macro FDEV_SETUP_STREAM() exists that can be used to initialized a FILE object. The floating-point implementations of vfscanf() and vfprintf() now allocate their conversion buffer on the stack, so they do not need malloc() anymore either.
• An API has been added to track the library version number. See the documentation of the new header file <avr/version.h>.
• Update the build system to recent versions of autoconf/automake; the old doconf and domake scripts are gone now (i.e., standard configure and make just work), reconf has been renamed to bootstrap.
• Update the documentation system to doxygen >= 1.4.1.
• Major overhaul of the documentation, new layout of the HTML pages, several clarifications and additions
• Add support for the following new devices (depending on the ability of the compiler/binutils to handle them):
  • AT90CAN32/64
  • AT90PWM2(B)/3(B)
  • ATmega329/3290/649/6490
  • ATtiny25/45/85
  • ATmega164/324/644
  • ATmega640/1280/1281
• The library is now compiled with -Os for avr3 and avr5 MCUs (i.e. for those with > 8 KB of ROM); used to be -O3 before.

Please refer to the documentation for details.