Re: RFA: PR 68913: Provide weak version of __fread_chk for PR61886 test

[Jeff Law <law at redhat dot com>]

On 01/07/2016 06:37 AM, Nick Clifton wrote:
> Hi Jeff,
>
> > But does the existence of the weak fread_chk change the interactions
> > inside IPA & LTO in such a way as to compromise the test?
> >
> > One way to find out would be to check out a compiler before Honza's
> > change which fixed 61886, verify the test as written fails, verify the
> > test with your new weak symbol also fails.  Honza didn't fix this until
> > early December, so you don't have to go terribly far back.
>
> Darn you and your clever brain...  You were right.  My patch prevents
> the test from triggering the bug that was fixed by Honza's patch.
I wouldn't say clever, just paranoid around this particular issue.
> So I have come up with an alternative, simpler patch - define the
> __fread_chk symbol on the linker command line (overriding any definition
> that may or may not be present in the target's C library). Since this is
> a (final) link time redefinition rather than a compile time one, it does
> not interfere with the IPA/LTO code.
>
> This patch works.  I tested it both with an x86_64-pc-linux-gnu
> toolchain and an arm-eabi toolchain both before Honza's patch was
> committed (both targets fail the test) and with today's gcc sources
> (both targets pass the test).
>
> OK to apply ?
As folks noted, I think this is still specific to the linker in use. 
Does it make sense to just limit this test to specific platforms, 
perhaps just x86/i686 linux for now.  68913 mentions ppc64-linux fails, 
it'd be nice to know why since I'd expect that has the _chk symbols.



jeff