|Ada 95 Quality and Style Guide||Chapter 7|
7.1.6 Implementation-Added Features
Avoid the use of vendor-supplied packages.
Avoid the use of features added to the predefined packages that are not specified in the Ada language definition or Specialized Needs Annexes.
Vendor-added features are not likely to be provided by other implementations. Even if a majority of vendors eventually provide similar additional features, they are unlikely to have identical formulations. Indeed, different vendors may use the same formulation for (semantically) entirely different features. See Guideline 7.5.2 for further information on vendor-supplied exceptions.
Ada has introduced a number of new pragmas and attributes that were not present in Ada 83 (Ada Reference Manual 1983). These new pragmas and attributes may clash with implementation-defined pragmas and attributes.
There are many kinds of applications that require the use of these features. Examples include multilingual systems that standardize on a vendor's file system, applications that are closely integrated with vendor products (i.e., user interfaces), and embedded systems for performance reasons. Isolate the use of these features into packages.
If a vendor-supplied package is provided in compilable source code form, use of the package does not make a program nonportable provided that the package does not contain any nonportable code and can be lawfully included in your program.
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