Re: [avr-libc-dev] [bug #44869] trunk doesn't work with gcc 5.1.0-RC-20150412

[Sivanupandi, Pitchumani]

> From: Joerg Wunsch [mailto:address@hidden
> > Yes. If we release from revision r2473 it will work with gcc-5.1, not
> trunk.
> >
> > If we release from last revision r2474, it will work with gcc trunk, not
> gcc-5.1.
> >
> > So, we need to change avr-libc to build with all versions of gcc.
> 
> Ick. :-((
> 
> > > What's the state with respect to compiling that using older compiler
> > > versions?
> 
> > Lib directories and startup file names are decided in bootstrapping.
> > But valid compiler is checked in configure. So, auto detection of
> > compiler and configure libs/startups will require infrastructure
> > change.
> 
> I see.  But at least, if I bootstrap on a certain compiler, then
> configure, it will be able to build there, yes?
>
> > Do you have any input on this?
> 
> Am I right in the assumption that the main issue is that ./devtools/gen-
> avr-lib-tree.sh is called only when bootstrapping?  I guess it might be
> possible to (re-)do this at configure time.  It means the script needs to
> be delivered into the final release tarball, but that's going to be the
> least problem.
> 
> I would (obviously) much prefer that the library can be built on at least
> a few recent/stable versions of GCC (say, 4.8 through 5.1), as opposed to
> just a single (matching) version.

It is possible to auto-detect the compiler version and enable device library.

Attached a patch.

It checks for gcc version (less than 5.0, 5.1.0 or greater). If version 
is >= 5.0.0 then device library is enabled.

A configure option "--enable-device-lib" is added so that users can enable
device library even with older versions of gcc (if they backport device
library patch).

Following table illustrates the crt file and device library name/layout
expected by gcc. AVR-LibC configure is updated to follow this layout.

Example: atmega1280
+----------------+-------------+-------------------------+-----------------+
|                | GCC < 5.0.0 | GCC 5.1.0               | Others          |
+----------------+-------------+-------------------------+-----------------+
| crt file       | crtm1280.o  | crtm1280.o              | crtatmega1280.o |
+----------------+-------------+-------------------------+-----------------+
| device library |             | dev/atmega1280/libdev.a | libatmega1280.a |
+----------------+-------------+-------------------------+-----------------+

Is the attached patch Ok?

Regards,
Pitchumani

detect-gcc-version-and-build-device-lib.patch
Description: detect-gcc-version-and-build-device-lib.patch