Fix copy that was causing stack corruption.

The buffer created for reversing the byte order was not large enough
to hold the number of bytes in the type so the overspill was corrupting
the stack.
Refs #14106

Framework/DataHandling/src/LoadFITS.cpp

@@ -8,6 +8,7 @@
 #include "MantidKernel/UnitFactory.h"
 
 #include <boost/algorithm/string.hpp>
+#include <boost/scoped_ptr.hpp>
 
 #include <Poco/BinaryReader.h>
 #include <Poco/FileStream.h>
@@ -801,29 +802,27 @@ void LoadFITS::readDataToWorkspace(const FITSInfo &fileInfo, double cmpp,
       size_t start =
           ((i * (bytespp)) * fileInfo.axisPixelLengths[1]) + (j * (bytespp));
 
-      char tmpbuf;
-      char *tmp = &tmpbuf;
-
       // Reverse byte order of current value
-      std::reverse_copy(buffer8 + start, buffer8 + start + bytespp, tmp);
+      boost::scoped_ptr<uint8_t> tmp(new uint8_t[bytespp]);
+      std::reverse_copy(buffer8 + start, buffer8 + start + bytespp, tmp.get());
 
       double val = 0;
       if (fileInfo.bitsPerPixel == 8)
-        val = static_cast<double>(*reinterpret_cast<uint8_t *>(tmp));
+        val = static_cast<double>(*reinterpret_cast<uint8_t *>(tmp.get()));
       else if (fileInfo.bitsPerPixel == 16)
-        val = static_cast<double>(*reinterpret_cast<uint16_t *>(tmp));
+        val = static_cast<double>(*reinterpret_cast<uint16_t *>(tmp.get()));
       else if (fileInfo.bitsPerPixel == 32 && !fileInfo.isFloat)
-        val = static_cast<double>(*reinterpret_cast<uint32_t *>(tmp));
+        val = static_cast<double>(*reinterpret_cast<uint32_t *>(tmp.get()));
       else if (fileInfo.bitsPerPixel == 64 && !fileInfo.isFloat)
-        val = static_cast<double>(*reinterpret_cast<uint64_t *>(tmp));
+        val = static_cast<double>(*reinterpret_cast<uint64_t *>(tmp.get()));
 
       // cppcheck doesn't realise that these are safe casts
       else if (fileInfo.bitsPerPixel == 32 && fileInfo.isFloat) {
         // cppcheck-suppress invalidPointerCast
-        val = static_cast<double>(*reinterpret_cast<float *>(tmp));
+        val = static_cast<double>(*reinterpret_cast<float *>(tmp.get()));
       } else if (fileInfo.bitsPerPixel == 64 && fileInfo.isFloat) {
         // cppcheck-suppress invalidPointerCast
-        val = *reinterpret_cast<double *>(tmp);
+        val = *reinterpret_cast<double *>(tmp.get());
       }
 
       val = fileInfo.scale * val - fileInfo.offset;