7.4  Metadirectives

A metadirective is a directive that can specify multiple directive variants of which one may be conditionally selected to replace the metadirective based on the enclosing OpenMP context. A metadirective is replaced by a nothing directive or one of the directive variants specified by the when clauses or the otherwise clause. If no otherwise clause is specified the effect is as if one was specified without an associated directive variant.

The OpenMP context for a given metadirective is defined according to Section 7.1. The order of clauses that appear on a metadirective is significant and otherwise must be the last clause specified on a metadirective.

Replacement candidates are ordered according to the following rules in decreasing precedence:

• A candidate is before another one if the score associated with the context selector of the corresponding when clause is higher.
• A candidate that was explicitly specified is before one that was implicitly specified.
• Candidates are ordered according to the order in which they lexically appear on the metadirective.

The list of dynamic replacement candidates is the prefix of the sorted list of replacement candidates up to and including the first candidate for which the corresponding when clause has a static context selector. The first dynamic replacement candidate for which the corresponding when clause has a compatible context selector, according to the matching rules defined in Section 7.3, replaces the metadirective.

Restrictions

• Replacement of the metadirective with the directive variant associated with any of the dynamic replacement candidates must result in a conforming OpenMP program.
• Insertion of user code at the location of a metadirective must be allowed if the first dynamic replacement candidate does not have a static context selector.

• All items must be executable directives if the first dynamic replacement candidate does not have a static context selector.

  ∙ A metadirective that appears in the specification part of a subprogram must follow all variant-generating declarative directives that appear in the same specification part. ∙ All directive variants of a metadirective must be pure otherwise the metadirective is not pure.