Fix Nexus valgrind errors

[Russell Taylor]

While running valgrind for another reason on FindPeaksTest I noticed several memory errors being highlighted in the LoadNexusProcessed (and called) code:

==7181== Conditional jump or move depends on uninitialised value(s)
==7181==    at 0x4A07F59: strlen (mc_replace_strmem.c:403)
==7181==    by 0x3044A9E14B: std::string::operator=(char const*) (in /usr/lib64/libstdc++.so.6.0.13)
==7181==    by 0x79627E1: Mantid::NeXus::NXClass::getNextEntry() (NexusClasses.cpp:160)
==7181==    by 0x7962AAC: Mantid::NeXus::NXClass::readAllInfo() (NexusClasses.cpp:169)

==7181== Mismatched free() / delete / delete []
==7181==    at 0x4A05B26: operator delete[](void*) (vg_replace_malloc.c:515)
...
==7181==    by 0x68D8DF5: boost::shared_array<int>::~shared_array() (shared_array.hpp:47)
==7181==    by 0x68D8E28: Mantid::NeXus::NXDataSetTyped<int>::~NXDataSetTyped() (NexusClasses.h:198)
==7181==    by 0x697727F: Mantid::DataHandling::LoadNexusProcessed::readInstrumentGroup(Mantid::NeXus::NXEntry&, boost::shared_ptr<Mantid::API::MatrixWorkspace>) (LoadNexusProcessed.cpp:1163)

[Russell Taylor]

Re #7857. Fix invalid initialisation of shared_array.

A boost::shared_array should be initialised with NULL or a pointer to an array, so what was there were errors. In fact, in these cases there's no need for any initialisation, only declaration.

Changeset: e8622703cfde583bff5ee3bef6973e75cc20275b

[Russell Taylor]

Re #7857. Only initialise struct members if status is NX_OK.

If there is no next entry, NXgetnextentry will not have set the nxname & nxclass variables that were passed to it. Therefore, a valgrind complaint is avoided by checking for success & only coping the variables on success.

Changeset: 403a10940f150757258a28d33aaa335bc4dc5395

[Russell Taylor]

Re #7857. Remove nonsense.

Nothing to do with this ticket, but this gave a ton of warnings when built with clang and if you look at it it was clearly nonsense. (N.B. nd is properly initialised later in the constructor.)

Changeset: 85a22ba6a7d2560c65cac14bece2d13a8ba173cc

[Russell Taylor]

Tester: Branch is feature/7857_nexus_valgrind_errors.

I suggest testing this by inspection of the code and agreement that things that were wrong before are now right! If you really wanted to you could run valgrind (vanilla, not memcheck or anythin) over the LoadNexusProcessedTest and observe lots of errors before the changes and none after.

[Michael Reuter]

The changes look good and the before and after on valgrind is great!

[Michael Reuter]

Merge remote-tracking branch 'origin/feature/7857_nexus_valgrind_errors'

[Stuart Campbell]

This ticket has been transferred to github issue ​8702