From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Sent: 26 January 2021 16:05 > > On Tue, Jan 26, 2021 at 09:46:51AM -0600, Josh Poimboeuf wrote: > > On Tue, Jan 26, 2021 at 04:15:37PM +0100, Peter Zijlstra wrote: > > > On Tue, Jan 26, 2021 at 08:51:55AM -0600, Josh Poimboeuf wrote: > > > > User space mixes compiler versions all the time. The C ABI is stable. > > > > > > > > What specifically is the harder issue you're referring to? > > > > > > I don't think the C ABI captures nearly enough. Imagine trying to mix a > > > compiler with and without asm-goto support (ok, we fail to build without > > > by now, but just imagine). > > > > > > No C ABI violated, but having that GCC extention vs not having it > > > radically changes the kernel ABI. > > > > > > I think I'm with Greg here, just don't do it. > > > > Ok, thank you for an actual example. asm goto is a good one. > > > > But it's not a cut-and-dry issue. Otherwise how could modversions > > possibly work? > > > > So yes, we should enforce GCC versions, but I still haven't seen a > > reason it should be more than just "same compiler and *major* version". > > Why bother? rebuilding the kernel and all modules is a matter of 10 > minutes at most on a decently beefy build box. > > What actual problem are we trying to solve here? People build modules to load into disrto-provided kernels. I'd have though the compiler would need to support the same options as that used to build the kernel - but not necessarily be exactly the same version. Ignoring compiler bugs (which will bight you if the compiler you have is broken) then a newer compiler ought to be fine. Or a kernel might have been built with config options that don't require features of the compiler being used - so that modules can be built with an older compiler. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
