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Diffstat (limited to 'TAO/CIAO/CCF/Documentation/DesignNotes')
| -rw-r--r-- | TAO/CIAO/CCF/Documentation/DesignNotes | 192 |
1 files changed, 96 insertions, 96 deletions
diff --git a/TAO/CIAO/CCF/Documentation/DesignNotes b/TAO/CIAO/CCF/Documentation/DesignNotes index b81778b5ba4..1cf74e88400 100644 --- a/TAO/CIAO/CCF/Documentation/DesignNotes +++ b/TAO/CIAO/CCF/Documentation/DesignNotes @@ -1,14 +1,14 @@ Note: this file is somewhat outdated -Intention of this file is to capture and document CIDL complier design +Intention of this file is to capture and document CIDL complier design ideas/decisions. Conceptual parts of CIDL compiler design ---------------------------------------- Option Parser Consists of option parser and option - database. + database. C Preprocessor Interfacing Represents mechanism of preprocessing cidl files. @@ -30,10 +30,10 @@ Semantic Analyzer Traverses Syntax Tree and performs semantic expansions. -Code Generation Stream Stream to output generated code to. Used +Code Generation Stream Stream to output generated code to. Used by concrete Code Generators -Code Generators +Code Generators { Executor Mapping Generator Generator for local executor mapping. @@ -48,7 +48,7 @@ Code Generators } Compiler driver Establishes order of execution of - different components as part of + different components as part of compilation process. @@ -63,8 +63,8 @@ How everything works together cidl file and generates Syntax Tree by means of semantic rules. (4) At this point we have Syntax Tree corresponding to the original cidl - file. Compiler Driver executes Executor Mapping Generator, - Executor Implementation Generator and Skeleton Thunk Generator on + file. Compiler Driver executes Executor Mapping Generator, + Executor Implementation Generator and Skeleton Thunk Generator on Syntax Tree. @@ -72,7 +72,7 @@ How everything works together General Design Ideas/Decision ------------- -[IDEA]: There is an effort to use autoconf/automake in ACE/TAO. Maybe it's +[IDEA]: There is an effort to use autoconf/automake in ACE/TAO. Maybe it's a good idea to start using it with CIDLC? There is one side advantage of this approach: if we decide to embed GCC CPP then we will have to use configure (or otherwise ACE-ify the code which doesn't sound like @@ -81,7 +81,7 @@ General Design Ideas/Decision [IDEA]: CIDLC is a prototype for a new IDLC, PSDLC and IfR model. Here are basic concepts: - - use common IDL grammar, semantic rules and syntax tree nodes + - use common IDL grammar, semantic rules and syntax tree nodes for IDLC, CIDLC, PSDLC and IfR. Possibly have several libraries for example ast_idl-2.so, ast_idl-3.so, scaner_idl-2.so scaner_idl-3.so, parser_idl-2.so, parser_idl-3.so. Dependency @@ -102,16 +102,16 @@ General Design Ideas/Decision ---------parser_idl-3.so--------- Same idea applies for CIDL and PSDL. - - - use the same internal representation (syntax tree) in all + + - use the same internal representation (syntax tree) in all compilers and IfR. This way at some stage if we will need to make one of the compilers IfR-integrated (import keyword?) then it will be a much easier task than it's now. This internal - representation may also be usable in typecodes + representation may also be usable in typecodes + + @@ boris: not clear to me. - @@ boris: not clear to me. - @@ jeff: A typecode is like a piece of the Syntax Tree with these exceptions - @@ -125,44 +125,44 @@ General Design Ideas/Decision different classes than used to compose the ST itself. @@ boris: Ok, let me see if I got it right. So when typecode - is kept in parsed state (as opposite to binary) (btw, when + is kept in parsed state (as opposite to binary) (btw, when does it happen?) it makes sense to apply the same techniques (if in fact not the same ST nodes and traversal mechs) as for XIDL compilation. [IDEA]: We should be consistent with the way external compilers that we call report errors. For now those are CPP and IDLC. - + Option Parser ------------- [IDEA]: Use Spirit parser framework to generate option parser. -[IDEA]: Option Database is probably a singleton. +[IDEA]: Option Database is probably a singleton. - @@ jeff: This is a good idea, especially when passing some of the - options to a preprocessor or spawned IDL compier. But I think we - will still need 'state' classes for the front and back ends (to - hold values set by command line options and default values) so + @@ jeff: This is a good idea, especially when passing some of the + options to a preprocessor or spawned IDL compier. But I think we + will still need 'state' classes for the front and back ends (to + hold values set by command line options and default values) so we can keep them decoupled). - @@ boris: I understand what you mean. Though I think we will be + @@ boris: I understand what you mean. Though I think we will be able to do with one 'runtime database'. Each 'compiler module' will be able to populate its 'namespace' with (1) default - values, (2) with module-specific options and (3) arbitrary + values, (2) with module-specific options and (3) arbitrary runtime information. I will present prototopy design shortly. - + [IDEA]: It seems we will have to execute at least two external programs as part of CIDLC execution: CPP and IDLC. Why wouldn't we follow GCC specs model (gcc -dumpspecs). Here are candidates to be put into - specs: + specs: - default CPP name and options - default IDLC name and options - default file extensions and formats for different mappings - - other ideas? + - other ideas? [IDEA]: Provide short and long option names (e.g. -o and --output-dir) for every option (maybe except -I, -D, etc). @@ -188,9 +188,9 @@ C Preprocessor Interfacing IDL Compiler Interfacing ------------------------ -[IDEA]: Same as for CPP: Can we use pipes? +[IDEA]: Same as for CPP: Can we use pipes? - @@ jeff: check with Nanbor on this. I think there may be CCM/CIAO + @@ jeff: check with Nanbor on this. I think there may be CCM/CIAO use cases where we need the intermediate IDL file. [IDEA]: Will need a mechanism to pass options to IDLC from CIDLC command @@ -207,7 +207,7 @@ Scanner iterator"-based scanner. So this basically mean that we may have to keep the whole sequence in memory. BTW, this is another good reason to have scanner: if we manage to make scanner a predictable parser - (i.e. no backtracking) then we don't have to keep the whole + (i.e. no backtracking) then we don't have to keep the whole preprocessed cidl file in memory. @@ -221,17 +221,17 @@ Parser much easier to reuse/inherit even dynamically. Need to elaborate this idea. -[IDEA]: Use functors as semantic actions. This way we can specify (via +[IDEA]: Use functors as semantic actions. This way we can specify (via functor's data member) on which Syntax Tree they are working. Bad side: semantic rules are defined during grammar construction. However we can use a modification of the factory method pattern. - Better ideas? + Better ideas? @@ jeff: I think ST node creation with a factory is a good idea - another ST implementation could be plugged in, as long as it uses a factory with the same method names. - @@ boris: Right. In fact it's our 'improved' way of handling 'BE' + @@ boris: Right. In fact it's our 'improved' way of handling 'BE' usecases. @@ -242,23 +242,23 @@ Syntax Tree [IDEA]: Use interface repository model as a base for Syntax Tree hierarchy. [IDEA]: Currently (in IDLC) symbol lookup is accomplished by AST navigation, - and is probably the biggest single bottleneck in performance. Perhaps - a separate symbol table would be preferable. Also, lookups could be - specialized, e.g., for declaration, for references, and perhaps a + and is probably the biggest single bottleneck in performance. Perhaps + a separate symbol table would be preferable. Also, lookups could be + specialized, e.g., for declaration, for references, and perhaps a third type for argument-related lookups. [NOTE]: If we are to implement symbol tables then we need to think how we are going to inherit (extend) this tables. [NOTE]: Inheritance/supports graphs: these graphs need to be traversed at - several points in the back end. Currently they are rebuilt for each - use, using an n-squared algorithm. We could at least build them only - once for each interface/valuetype, perhaps even with a better - algorithm. It could be integrated into inheritance/supports error - checking at node creation time, which also be streamlined. - - @@ boris: Well, I think we should design our Syntax Tree so that - every interface/valuetype has a list (flat?) of interfaces it + several points in the back end. Currently they are rebuilt for each + use, using an n-squared algorithm. We could at least build them only + once for each interface/valuetype, perhaps even with a better + algorithm. It could be integrated into inheritance/supports error + checking at node creation time, which also be streamlined. + + @@ boris: Well, I think we should design our Syntax Tree so that + every interface/valuetype has a list (flat?) of interfaces it inherits from/supports. [IDEA]: We will probably want to use factories to instantiate Syntax Tree @@ -272,19 +272,19 @@ Common Syntax Tree traversal Design Ideas/Decision [IDEA] If we specify Syntax Tree traversal facility then we will be able to specify (or even plug dynamically) Syntax Tree traversal agents - that may not only generate something but also annotate or modify + that may not only generate something but also annotate or modify Syntax Tree. We are already using this technique for a number of features (e.g. AMI, IDL3 extension, what else?) but all these agents are hardwired inside TAO IDLC. If we have this facility then we will be able to produce modular and highly extensible design. Notes: - Some traversal agents can change Syntax Tree so that it will be - unusable by some later traversal agents. So maybe the more - generic approach would be to produce new Syntax Tree? + unusable by some later traversal agents. So maybe the more + generic approach would be to produce new Syntax Tree? - @@ jeff: Yes, say for example that we were using a common ST - representation for the IDL compiler and the IFR. We would not - want to send the extra AMI nodes to the IFR so in that case + @@ jeff: Yes, say for example that we were using a common ST + representation for the IDL compiler and the IFR. We would not + want to send the extra AMI nodes to the IFR so in that case simple modification of the ST might not be best. [IDEA] Need a generic name for "Syntax Tree Traversal Agents". What about @@ -306,16 +306,16 @@ Code Generation Stream will result in a generated code like this: namespace N - { - ... + { + ... long foo (long arg0, long arg1) { return arg0 + arg1; } - - ... + + ... } Note that no special actions were taken to ensure proper indentation. @@ -336,34 +336,34 @@ Code Generators @@ boris: I would say may not always be correct - However, for purposes of type coercion and other checking (such as - for positive integer values in string, array and sequence bounds) + However, for purposes of type coercion and other checking (such as + for positive integer values in string, array and sequence bounds) evaluation must be done internally. - + @@ boris: note that evaluation is needed to only verify that things - are correct. You don't have to (shouldn't?) substitute original + are correct. You don't have to (shouldn't?) substitute original (const) expression with what's been evaluated. - @@ jeff: it may be necessary in some cases to append 'f' or 'U' to + @@ jeff: it may be necessary in some cases to append 'f' or 'U' to a generated number to avoid a C++ compiler warning. @@ boris: shouldn't this 'f' and 'U' be in IDL as well? [IDEA] I wonder if it's a good idea to use a separate pass over syntax tree - for semantic checking (e.g. type coercion, positive values for - sequence bounds). + for semantic checking (e.g. type coercion, positive values for + sequence bounds). - @@ jeff: This may hurt performance a little - more lookups - but it + @@ jeff: This may hurt performance a little - more lookups - but it will improve error reporting. - + @@ boris: As we dicussed earlier this pass could be used to do 'semantic expansions' (e.g. calculate a flat list of interface's children, etc). Also I don't think we should worry about speed very much here (of course I don't say we have to be stupid ;-) In fact if we are trading better design vs faster compilation at this stage we should always go for better design. - + Executor Mapping Generator -------------------------- @@ -394,66 +394,66 @@ Vault Some thoughts from Jeff that I are not directly related to CIDLC and are rather current IDLC design defects: -* AMI/AMH implied IDL: more can be done in the BE preprocessing pass, - hopefully eliminating a big chunk of the huge volume of AMI/AMH visitor - code. The implied IDL generated for CCM types, for example, leaves almost +* AMI/AMH implied IDL: more can be done in the BE preprocessing pass, + hopefully eliminating a big chunk of the huge volume of AMI/AMH visitor + code. The implied IDL generated for CCM types, for example, leaves almost nothing extra for the visitors to do. -* Fwd decl redefinition: forward declaration nodes all initially contain a - heap-allocated dummy full-definition member, later replaced by a copy +* Fwd decl redefinition: forward declaration nodes all initially contain a + heap-allocated dummy full-definition member, later replaced by a copy of the full definition. This needs to be streamlined. -* Memory leaks: inconsistent copying/passing policies make it almost - impossible to eliminate the huge number of leaks. The front end will be - more and more reused, and it may be desirable to make it executable as a - function call, in which case it will important to eliminate the leaks. - Perhaps copying of AST nodes can be eliminated with reference counting or +* Memory leaks: inconsistent copying/passing policies make it almost + impossible to eliminate the huge number of leaks. The front end will be + more and more reused, and it may be desirable to make it executable as a + function call, in which case it will important to eliminate the leaks. + Perhaps copying of AST nodes can be eliminated with reference counting or just with careful management, similarly for string identifiers and literals. - Destroy() methods have been put in all the node classes, and are called - recursively from the AST root at destruction time, but they are far from + Destroy() methods have been put in all the node classes, and are called + recursively from the AST root at destruction time, but they are far from doing a complete job. -* Visitor instantiation: the huge visitor factory has already been much - reduced, and the huge enum of context state values is being reduced. - However there will still be an abundance of switch statements at nearly - every instance of visitor creation at scope nesting. We could make better +* Visitor instantiation: the huge visitor factory has already been much + reduced, and the huge enum of context state values is being reduced. + However there will still be an abundance of switch statements at nearly + every instance of visitor creation at scope nesting. We could make better use of polymorphism to get rid of them. * Node narrowing: instead of the impenetrable macros we use now, we - could either generate valuetype-like downcast methods for the (C)IDL + could either generate valuetype-like downcast methods for the (C)IDL types, or we could just use dynamic_cast. * Error reporting: making error messages more informative, and error recovery - could both be a lot better, as they are in most other IDL compilers. If a - recursive descent parser is used (such as Spirit), there is a simple + could both be a lot better, as they are in most other IDL compilers. If a + recursive descent parser is used (such as Spirit), there is a simple generic algorithm for error recovery. -* FE/BE node classes: if BE node classes are implemented at all, there should - be a complete separation of concerns - BE node classes should contain only - info related to code generation, and FE node classes should contain only - info related to the AST representation. As the front end becomes more - modular and reusable, this will become more and more necessary. +* FE/BE node classes: if BE node classes are implemented at all, there should + be a complete separation of concerns - BE node classes should contain only + info related to code generation, and FE node classes should contain only + info related to the AST representation. As the front end becomes more + modular and reusable, this will become more and more necessary. @@ boris: It doesn't seem we will need two separate and parallel hierarhies. * Undefined fwd decls: now that we have dropped support for platforms without - namespaces, the code generated for fwd declarations not defined in the same - translation unit can be much improved, most likely by the elimination of + namespaces, the code generated for fwd declarations not defined in the same + translation unit can be much improved, most likely by the elimination of generated flat-name global methods, and perhaps other improvements as well. -* Strategized code generation: many places now have either lots of - duplication, or an explosion of branching in a single visitor. Adding code - generation for use cases incrementally may give us an opportunity to +* Strategized code generation: many places now have either lots of + duplication, or an explosion of branching in a single visitor. Adding code + generation for use cases incrementally may give us an opportunity to refactor and strategize it better. -* Node generator: this class does nothing more than call 'new' and pass - unchanged the arguments it gets to the appropriate constructor - it can be +* Node generator: this class does nothing more than call 'new' and pass + unchanged the arguments it gets to the appropriate constructor - it can be eliminated. -* Virtual methods: there are many member functions in the IDL compiler that +* Virtual methods: there are many member functions in the IDL compiler that are needlessly virtual. -* Misc. leveraging: redesign of mechanisms listed above can have an effect +* Misc. leveraging: redesign of mechanisms listed above can have an effect on other mechanisms, such as the handling of pragma prefix, typeprefix, and reopened modules. |