6.32 RM 13.13.2(17): Stream Oriented Attributes

"If a stream element is the same size as a storage element, then the normal in-memory representation should be used by Read and Write for scalar objects. Otherwise, Read and Write should use the smallest number of stream elements needed to represent all values in the base range of the scalar type."

Followed. By default, GNAT uses the interpretation suggested by AI-195, which specifies using the size of the first subtype. However, such an implementation is based on direct binary representations and is therefore target- and endianness-dependent. To address this issue, GNAT also supplies an alternate implementation of the stream attributes Read and Write, which uses the target-independent XDR standard representation for scalar types.

The XDR implementation is provided as an alternative body of the System.Stream_Attributes package, in the file s-stratt-xdr.adb in the GNAT library. There is no s-stratt-xdr.ads file. In order to install the XDR implementation, do the following:

• * Replace the default implementation of the System.Stream_Attributes package with the XDR implementation. For example on a Unix platform issue the commands:

  $ mv s-stratt.adb s-stratt-default.adb
  $ mv s-stratt-xdr.adb s-stratt.adb
  

• * Rebuild the GNAT run-time library as documented in the `GNAT and Libraries' section of the GNAT User’s Guide.