[ET Trac] [Einstein Toolkit] #1339: Memory alignment in CarpetLib failing

[Einstein Toolkit]

#1339: Memory alignment in CarpetLib failing
---------------------+------------------------------------------------------
  Reporter:  rhaas   |       Owner:  eschnett
      Type:  defect  |      Status:  new     
  Priority:  minor   |   Milestone:          
 Component:  Carpet  |     Version:          
Resolution:          |    Keywords:          
---------------------+------------------------------------------------------

Comment (by eschnett):

 New patch:

 {{{
 diff --git a/Carpet/CarpetLib/src/mem.cc b/Carpet/CarpetLib/src/mem.cc
 index 89d8fb2..be28d20 100644
 --- a/Carpet/CarpetLib/src/mem.cc
 +++ b/Carpet/CarpetLib/src/mem.cc
 @@ -105,6 +105,7 @@ mem (size_t const vectorlength, size_t const nelems,
        size_t const max_cache_linesize = get_max_cache_linesize();
        size_t const vector_size = CCTK_REAL_VEC_SIZE * sizeof(T);
        size_t const alignment = align_up(max_cache_linesize, vector_size);
 +      assert(alignment >= 1);
        // Safety check
        assert(alignment <= 1024);
        // Assume optimistically that operator new returns well-aligned
 @@ -123,7 +124,8 @@ mem (size_t const vectorlength, size_t const nelems,
        } else {
        allocate_with_alignment:
          // Operator new needs manual alignment
 -        size_t const max_padding = alignment / sizeof(T) - 1;
 +        size_t const max_padding = div_up(alignment, sizeof(T));
 +        assert((ptrdiff_t(max_padding) >= 0);
          storage_base_ = new T [vectorlength * nelems + max_padding];
          storage_ = (T*) (size_t(storage_base_ + max_padding) &
 ~(alignment-1));
          assert(size_t(storage_) >= size_t(storage_base_              )
 and
 }}}

 Operator new's alignment may be less than the type's size (if a type
 requires alignment less than its size, such as e.g. complex numbers).
 Since we assume that a type's alignment is at least its size, we need to
 request more storage.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1339#comment:5>
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