fix HDF5Reader build with MSVC

Sadly, variable-sized stack arrays are only a feature of C99, but not C++11,
so this patch uses std::vector instead.

source/adios2/engine/hdf5/HDF5ReaderP.cpp

@@ -14,6 +14,8 @@
 #include "adios2/common/ADIOSMPI.h"
 #include "adios2/helper/adiosFunctions.h" //CSVToVector
 
+#include <vector>
+
 namespace adios2
 {
 namespace core
@@ -146,7 +148,7 @@ size_t HDF5ReaderP::ReadDataset(hid_t dataSetId, hid_t h5Type,
     }
     else
     {
-        hsize_t start[ndims], count[ndims], stride[ndims];
+        std::vector<hsize_t> start(ndims), count(ndims), stride(ndims);
         bool isOrderC = helper::IsRowMajor(m_IO.m_HostLanguage);
 
         for (int i = 0; i < ndims; i++)
@@ -164,12 +166,12 @@ size_t HDF5ReaderP::ReadDataset(hid_t dataSetId, hid_t h5Type,
             slabsize *= count[i];
             stride[i] = 1;
         }
-        hid_t ret = H5Sselect_hyperslab(fileSpace, H5S_SELECT_SET, start,
-                                        stride, count, NULL);
+        hid_t ret = H5Sselect_hyperslab(fileSpace, H5S_SELECT_SET, start.data(),
+                                        stride.data(), count.data(), NULL);
         if (ret < 0)
             return 0;
 
-        hid_t memDataSpace = H5Screate_simple(ndims, count, NULL);
+        hid_t memDataSpace = H5Screate_simple(ndims, count.data(), NULL);
         interop::HDF5TypeGuard g_mds(memDataSpace, interop::E_H5_SPACE);
 
         int elementsRead = 1;

source/adios2/toolkit/interop/hdf5/HDF5Common.cpp

@@ -15,6 +15,7 @@
 #include <ios>
 #include <iostream>
 #include <stdexcept>
+#include <vector>
 
 #include "adios2/common/ADIOSMPI.h"
 #include "adios2/helper/adiosFunctions.h" // IsRowMajor
@@ -419,8 +420,8 @@ void HDF5Common::AddVar(core::IO &io, std::string const &name, hid_t datasetId,
     {
         hid_t dspace = H5Dget_space(datasetId);
         const int ndims = H5Sget_simple_extent_ndims(dspace);
-        hsize_t dims[ndims];
-        H5Sget_simple_extent_dims(dspace, dims, NULL);
+        std::vector<hsize_t> dims(ndims);
+        H5Sget_simple_extent_dims(dspace, dims.data(), NULL);
         H5Sclose(dspace);
 
         Dims shape;