Re: [PATCH] Force building with -fno-common

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 7/8/21 3:57 PM, Florian Weimer via Libc-alpha wrote:
> As a result, is not necessary to specify __attribute__ ((nocommon))
> on individual definitions.
> 
> GCC 10 defaults to -fno-common on all architectures except ARC,
> but this change is compatible with older GCC versions and ARC, too.
> 
> Not sure if this is still appropriate at this time for glibc 2.34, but
> this commit simplifies compatibility symbol work, by reducing GCC
> version and architecture divergence.
> 
> Tested on i686-linux-gnu and x86_64-linux.  Tested with a full bootstrap
> cycle with build-many-glibc.py using the combinations GCC 8/binutils 2.32
> and GCC 7/binutils 2.33.  There are some build failures, but they appear
> to be unrelated to this change.

Carlos clarified that non-ABI changes are OK during the slushy freeze, 
but you could wait on him for additional approval.

I did a build on x86_64 to verify that the resulting binaries are 
identical (since -fno-common should be nop for gcc11) but turns out 
they're not.  I haven't yet looked at the nature of the change since 
they could be benign but it still was surprising.

Siddhesh