RFR(xs): 8145114: const-correctness for ucontext_t* reading functions

[David Holmes]

On 11/12/2015 10:58 PM, Thomas Stüfe wrote:
> Hi David,
>
> that was an oversight. see new webrev:
>
> http://cr.openjdk.java.net/~stuefe/webrevs/8145114-const-correctness-ucontext/webrev.01/webrev/
>
> and the delta to webrev 00:
>
> http://cr.openjdk.java.net/~stuefe/webrevs/8145114-const-correctness-ucontext/webrev.00-01/

That looks fine but ... I'm looking at other uses of ucontext_t and 
wondering if they are missing const?

JavaThread::pd_get_top_frame ?

./os/linux/vm/osThread_linux.hpp:  ucontext_t* _ucontext;
./os/linux/vm/osThread_linux.hpp:  ucontext_t* ucontext() const 
    { return _ucontext; }
./os/linux/vm/osThread_linux.hpp:  void set_ucontext(ucontext_t* ptr) 
    { _ucontext = ptr;  }

etc

Thanks,
David

> Thanks, Thomas
>
> On Fri, Dec 11, 2015 at 11:21 AM, David Holmes <david.holmes at oracle.com
> <mailto:david.holmes at oracle.com>> wrote:
>
>     Hi Thomas,
>
>     In:
>
>     ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
>                          intptr_t** ret_sp, intptr_t** ret_fp) {
>        ExtendedPC  epc;
>        ucontext_t* uc = (ucontext_t*)ucVoid;
>
>
>     is there some reason these ucontext_t's were not made const?
>
>     Thanks,
>     David
>
>     On 11/12/2015 7:57 PM, Thomas Stüfe wrote:
>
>         Hi David,
>
>         On Fri, Dec 11, 2015 at 10:35 AM, David Holmes
>         <david.holmes at oracle.com <mailto:david.holmes at oracle.com>
>         <mailto:david.holmes at oracle.com
>         <mailto:david.holmes at oracle.com>>> wrote:
>
>              Hi Thomas,
>
>              This seems okay. To be honest I'm not sure of the
>         usefulness but it
>              certainly isn't harmful :)
>
>              I'll prepare similar changes to our internal platforms and
>         run it
>              all through JPRT.
>
>              Thanks,
>              David
>
>
>              On 11/12/2015 5:16 PM, Thomas Stüfe wrote:
>
>                  Hi all,
>
>                  please review this large-but-trivial change:
>
>                  Bug: https://bugs.openjdk.java.net/browse/JDK-8145114
>                  webrev:
>         http://cr.openjdk.java.net/~stuefe/webrevs/8145114-const-correctness-ucontext/webrev.00/webrev/index.html
>
>                  Even though many files are involved, the changes are very
>                  trivial. The
>                  change takes care of declaring ucontext_t pointers as
>         const for
>                  all utility
>                  functions which do not change the context (which are
>         most of them).
>
>                  This fix was motivated by me wasting time in an error
>         situation
>                  on AIX
>                  where I accidentally changed the register values in the
>         context
>                  before
>                  printing them to the hs-err file.
>
>                  And, like pulling a thread from a ball of yarn, the
>         change got
>                  bigger and
>                  bigger... like it is once one starts to fix const
>         issues. But
>                  the fixes in
>                  this case involve the bottom functions and should not
>         force any
>                  new casts
>                  upon anyone.
>
>                  I did build the change on the following platforms:
>                  AIX
>                  Linux x64 (with and without ZERO)
>                  Linux ppc
>                  OSX
>                  Solaris Sparc and x64
>
>                  and all did build successfully.
>
>                  Kind Regards, Thomas
>
>
>