[PATCH] Allow building if libsanitizer on RHEL5 (i.e. with 2.6.18-ish kernel headers)

[Richard Biener]

On Fri, Dec 6, 2013 at 2:04 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Fri, Dec 06, 2013 at 01:52:29PM +0100, Richard Biener wrote:
>> > Note that testing still shows some issues, e.g. because the
>> > kThreadDescriptorSize change has not been applied.  But it at least builds
>> > and for many tests works.
>>
>> What's wrong with just copying the kernel headers 1:1?  ISTR that is what
>> kernel folks recommend if you use kernel APIs that don't have a glibc
>> correspondent.
>
> Well, for many things that is already the case, sanitizer_common has
> apparently it's own __sanitizer_* macros/constants/structures that
> are supposed to match kernel ones.  The problem is that
> the code is comparing them as compile time assertions against the kernel
> ones inside of the library code.  IMHO that is not a very good idea, much
> better would be just say a testcase that would include the sanitizer +
> kernel headers, guarded by recent enough LINUX_VERSION_CODE or configure or
> similar, so it wouldn't prevent library build on older kernel headers,
> the kernel ABI better be stable (only new things added, not size of
> structures/magic constants etc. changed from time to time).
>
> But Kostya is apparently not willing to do that, so this patch provides
> a workaround in non-compiler-rt maintained files.

:(

>> Of course you then need runtime checks on whether the running kernel
>> supports the API.
>
> Usually not, say if the structures/magic constants etc. are to wrap syscalls
> or ioctls etc., if kernel doesn't support those syscalls/ioctls, either
> nothing will use those syscalls/ioctls, or if it does, it will fail from the
> kernel, worst case you get some diagnostics from pre-syscall/ioctl wrapper,
> otherwise the kernel syscall/ioctl will just fail and post-syscall/ioctl
> wrapper will do likely nothing at all.

Yes, what I meant is that the code needs to expect things to fail dependent
on the kernel currently running.  Not sure if sanitizer does that.

Richard.

>         Jakub