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Category:Smalltalk: Difference between revisions
→Implementation
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== Implementation ==
Most Smalltalk implementations are based on a bytecode execution engine. Bytecode is emitted and stored in method objects by a compiler which is part of both the development and runtime environment (in contrast to external tools, like javac). Thus new methods can be generated and installed dynamically by reading scripts or a generator. Bytecodes are operations for a virtual stack based machine, which is either interpreted by an interpreter (part of the runtime system), or dynamically compiled to machine code (JITTER). Bytecode is not standardized and usually not compatible among dialects.
Some implementations support source-to-source compilation to C, JavaScript or Java. These may or may not show some limitations in the support for dynamic changes at execution time. Typically, the full dynamic bytecode is used for development, followed by a compilation phase for deployment/packaging.
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As message send performance is critical in Smalltalk, highly tuned cache mechanisms have been invented and are used: inline caches, polymorph inline caches, dynamic recompilation based on receiver and/or argument types etc.
Also block (aka lambda) creation and evaluation, especially the treatment of closed over variables has been in the focus of implementors. Algorithms similar to those found in sophisticated Lisp systems such as lambda lifting, inlining, stack allocation and heap migration etc. are also used in Smalltalk.
== Influences ==
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