Re: PR other/54324: allow bootstrapping with older compilers

[Steven Bosscher <stevenb dot gcc at gmail dot com>]

On Wed, Dec 12, 2012 at 6:07 AM, Aldy Hernandez wrote:
> I don't know how much of this is a fool's errand, and if we want to commit
> to supporting < GCC 3.4, but your patch suggested c++98, and GCC 3.2 claims
> such.

GCC 3.2 claims many things, but any GCC that has the old C++ parser
has known non-conformances. IMHO we should only support GCC versions
with the "new" C++ parser, i.e. GCC 3.4 and up.


>    Perhaps we could even deprecate ARG_UNUSED?

+1


> 2. gcov-io.c uses __builtin_popcountll and __builtin_clzll.  Older
>    GCC's do not have this.  For that matter, how does this even work on
>    non-GCC systems?

This'd be a bug.


> I really don't want to spend much more time on this, but at the same time, I
> don't want to throw away a day's work, especially if it could conceivably
> help us with (older) non-GCC bootstrap compilers.

I think the work you've done here is great, but even if you'd fix
these issues, there is very little that can be done to avoid the same
mistakes, or new ones, creeping back in and breaking builds with older
compilers.


> What are your thoughts on this?

At least: Thanks for uncovering the gcov-io.c bug :-)

Ciao!
Steven