consensus/ethash: fix bug in memoryMapFile

Author: fjl

consensus/ethash/ethash.go

@@ -113,10 +113,12 @@ func memoryMapFile(file *os.File, write bool) (mmap.MMap, []uint32, error) {
 		return nil, nil, err
 	}
 	// The file is now memory-mapped. Create a []uint32 view of the file.
-	header := (*reflect.SliceHeader)(unsafe.Pointer(&mem))
-	header.Len /= 4
-	header.Cap /= 4
-	return mem, *(*[]uint32)(unsafe.Pointer(header)), nil
+	var view []uint32
+	header := (*reflect.SliceHeader)(unsafe.Pointer(&view))
+	header.Data = (*reflect.SliceHeader)(unsafe.Pointer(&mem)).Data
+	header.Cap = len(mem) / 4
+	header.Len = header.Cap
+	return mem, view, nil
 }
 
 // memoryMapAndGenerate tries to memory map a temporary file of uint32s for write