Re: Minimum GCC version for building glibc

[Paul Eggert <eggert at cs dot ucla dot edu>]

On 11/04/2014 08:58 AM, Mike Frysinger wrote:
> what's the diff between 4.4 and 4.6 ?

4.5 didn't add much to the language: __builtin_unreachable is the only 
thing I'd write home about.

4.6 added anonymous structures and unions, _Static_assert, __attribute__ 
((leaf)), __attribute__((|callee_pop_aggregate)),|__int128 (as opposed 
to __int128_t), and better selection of diagnostics (e.g., #pragma GCC 
diagnostic push").  Anonymous structures and unions could make internals 
nicer, but one can always use non-anonymous. _Static_assert is very 
helpful but we could emulate it in pre-4.6 compilers by using something 
like Gnulib's verify module.  glibc already uses __attribute__ ((leaf)) 
if available.  The others are minor.  All in all, not a compelling case 
for changing the minimum version to 4.6.

4.7 adds atomics, and that's by far the most important thing that's been 
mentioned; I can easily see this motivating an upgrade.  Although 4.7 
also adds transactional memory, I don't know if we'd want to use it 
(it's termed "experimental").  A nicety is 4.7's support for stdalign.h 
and related operators, though that's not essential.