4.3 Thread safety in client libraries

4.3.2 Effects on the Dylan library

The definition of the Dylan library is not changed with the addition of the Threads library. The implementation ensures that all hidden global state (such as the symbol table and any generic function caches) is implicitly synchronized. Those functions in the Dylan library which are defined to modify the state of objects are not defined to provide implicit synchronization. However, implementations are expected to ensure that synchronization bugs in Dylan programs will not cause obscure errors that cannot be explained in terms of the semantics of Dylan language constructs.

The library guarantees that element and element-setter will be atomic for all of Dylan's non-stretchy built-in collection classes, and for <table>, except for subclasses of <string>, and limited collections where the elements are constrained to be either of a type for which slots and variables do not guarantee atomicity (see Section 4.2.1 on page 71) or a subtype of <character>, or of a proper subtype of <integer>. This design is intended to permit implementations to use efficient representations for element values, which use either more or less space than a normal Dylan value. It is undefined whether any of the other standard Dylan functions are atomic. Where atomicity is not guaranteed, clients should guard against unexpected behavior by using explicit synchronization, as appropriate.