Re: [XEN PATCH v9 08/30] build: fix enforce unique symbols for recent clang version

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Fri, Jan 28, 2022 at 01:43:38PM +0100, Jan Beulich wrote:
> On 28.01.2022 13:03, Anthony PERARD wrote:
> > On Thu, Jan 27, 2022 at 04:57:20PM +0100, Jan Beulich wrote:
> >> On 25.01.2022 12:00, Anthony PERARD wrote:
> >>> clang 6.0 and newer behave like gcc in regards for the FILE symbol, so
> >>> only the filename rather than the full path to the source file.
> >>>
> >>> clang 3.8.1-24 (in our debian:stretch container) and 3.5.0-10
> >>> (in our debian:jessie container) do store the full path to the source
> >>> file in the FILE symbol.
> >>>
> >>> Also, based on commit 81ecb38b83 ("build: provide option to
> >>> disambiguate symbol names"), which were using clang 5, the change of
> >>> behavior likely happened in clang 6.0.
> >>>
> >>> This means that we also need to check clang version to figure out
> >>> which command we need to use to redefine symbol.
> >>>
> >>> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> >>
> >> The "likely" in the description still worries me some. Roger, would
> >> you happen to know, or know of a way to find out for sure ("sure"
> >> not meaning to exclude the usual risk associated with version
> >> number checks)?
> > 
> > I found f5040b9685a7 ("Make .file directive to have basename only") as
> > part of LLVM's "release/6.x" branch (and "llvmorg-6.0.0" tag), but not
> > in "release/5.x".
> > 
> > https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fcommit%2Ff5040b9685a760e584c576e9185295e54635d51e&amp;data=04%7C01%7Canthony.perard%40citrix.com%7C1ce7898a15bb4024260008d9e25be6f9%7C335836de42ef43a2b145348c2ee9ca5b%7C0%7C0%7C637789706644173026%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=V73NmkJWAHpqlzY9sAysf6%2Fw7q8ik6twT6lMLgglR3s%3D&amp;reserved=0
> > 
> > This patch would seems to be the one changing the behavior. This still
> > suggest clang 6.0.
> 
> Oh, thanks for digging this out. May I suggest to replace (or delete)
> "likely" then in the description?

Maybe something like that? Or just delete the word might be enough.

    Also we have commit 81ecb38b83 ("build: provide option to
    disambiguate symbol names") which were using clang 5, and LLVM's
    commit f5040b9685a7 [1] ("Make .file directive to have basename
    only") which is part of "llvmorg-6.0.0" tag but not "release/5.x"
    branch. Both suggest that clang change of behavior happened with
    clang 6.0.

    [1] 
https://github.com/llvm/llvm-project/commit/f5040b9685a760e584c576e9185295e54635d51e

> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Thanks,

-- 
Anthony PERARD