Re: [PATCH v2 3/6] configure: add option to enable LTO

[Paolo Bonzini]

On 28/10/20 19:22, Daniele Buono wrote:
> If LTO is enabled with the wrong linker/ar:
> - with the checks, it will exit at configure with an error. I can change
> this in a warning and disabling LTO if preferred.
> - without the checks compilation will fail
> 
> If LTO is enabled with the wrong compiler (e.g. old gcc), you may get a
> bunch of warnings at compile time, and a binary that won't pass some of
> the tests in make check.

I think both of these count as user error or compiler bug, which we
generally don't protect against.

There is one exception.  We check if the C++ compiler driver can link
object files produced by the C compiler driver; this issue arises if the
driver used for compilation (C) is GCC and the driver used for linking
(C++) is clang, because GCC and clang's sanitizer libraries are not
compatible with each other.

I think however that in this case the problem is not one of
compatibility, but just a broken install, so I think we can just ignore
and just forward b_lto.

Paolo