Re: linking files compiled with older gfortran

[kamaraju kusumanchi <raju dot mailinglists at gmail dot com>]

On Mon, Jun 15, 2009 at 2:44 PM, Tobias Burnus<burnus@net-b.de> wrote:
> kamaraju kusumanchi wrote:
>> I have previously compiled a bunch of libraries (fftw3, blas, lapack,
>> lapack95, mpich2, openmpi etc.,) using gfortran 4.3.2. However, due to
>> a bug fixed in gfortran 4.4.0
>> http://gcc.gnu.org/ml/fortran/2009-06/msg00116.html I now want to
>> upgrade to gfortran 4.4.0 . My question is that should I recompile all
>> these libraries again? or will they work just fine? How good is the
>> gfortran's backward compatibility?
>>
>
> The libgfortran library which ships with GCC 4.4.x is backward
> compatible with programs/libraries compiled with GCC 4.3.x and the
> library which comes with the current developer version "4.5.0
> (experimental)" is compatible with GCC 4.3 and 4.4 compiled
> programs/libraries. Thus there is no need to recompile your libraries.
>
> Note of warning: GCC 4.5 is a developer release and there are plans to
> restructure the array descriptor (dope vector) during the 4.5 cycle (or
> during 4.6 if we don't manage). If that happens, there will be an
> incompatibility between 4.3.x/4.4.x and 4.5-before-change ?on one hand
> and 4.5-after-change on the other hand. As the library version number
> will then be bumped as well, the incompatibilities will show up at link
> time (link error).
>
> There are several reasons for changing the array descriptor: The changes
> are needed for some special cases in Fortran 90/95, for Fortran 2003 and
> Fortran 2008 (e.g. rank > 7 arrays, coarrays). Thus the change is
> inevitable. As arrays are at the heart of the gfortran library, one
> would need to replicate about 40% of the library in order to remain
> backward compatible. Due to the named symbols (on systems supporting
> it), it would be possible, but it seems to be a rather large burden.
> Therefore, current idea is to break the ABI compatibility between 4.4
> and 4.5.0-release ?[or if we don't manage time wise: between 4.5 and 4.6].
>
> Tobias
>

Thanks for the comprehensive explanation. I appreciate it. I hope
gfortran becomes stable enough soon.

raju