[Bug ada/55243] STAMP variable is not defined in t-avr

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55243

--- Comment #18 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-12-10 20:41:15 UTC ---
(In reply to comment #16)
>>> So t-multilib is autogenerated in the source tree during the build???
>> 
>> Jepp.  Top $(srcdir)/gcc/config/avr/t-multilib reads:
>> 
>> 
>> # Auto-generated Makefile Snip
>> # Generated by    : ./gcc/config/avr/genmultilib.awk
>> # Generated from  : ./gcc/config/avr/avr-mcus.def
>> # Used by         : tmake_file from Makefile and genmultilib
> 
> But this is a no-no, the compiler should be buildable with read-only sources
> once it is packaged in the release tarballs.


It works with read-only sources, provided everything is consistent.  Or are you
saying that a t-snip must not use $(STAMP)?

Actually, the PR boils down to the fact the STAMP is not defined, I am nut sure
if the compiler is supposed to build without STAMP.

>> Rationale is that avr-gcc supports an, IMHO, insane number of -mmcu=<device>. 
>> In order to keep various parts of the compiler in sync, some bits are
>> auto-generated, amongst them documentation, t-multilib and .opt parts.
>> 
>> Procedure is a move-if-change scheme, i.e. the auto-generated files are in the
>> repository and the procedure to build them is similar to building configure
>> from configure.ac and then putting both configure.ac /and/ configure into the
>> repo.
> 
> Building configure from configure.c isn't done at build time.
> 
> Either you generate t-multilib like configure and you can put it in $(srcdir)
> or you generate it at build time and you must put it in $(builddir).

Is basically follows an idea introduced with genopt.sh in

http://gcc.gnu.org/viewcvs?view=revision&revision=175248

Notice how t-avr builds avr-tables.opt, and that the latter is added to the
repo.