source: src/AST/porting.md @ 881f590

ADTarm-ehast-experimentalcleanup-dtorsenumforall-pointer-decayjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-exprpthread-emulationqualifiedEnum
Last change on this file since 881f590 was fdbd4fd, checked in by Aaron Moss <a3moss@…>, 5 years ago

Add dynamic_cast as method to ptr_base

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1# Porting notes for new AST #
2
3## Pointer Types ##
4* raw pointer `T*` is used for construction, but not storage
5* `ast::ptr_base<T,R>` is a pointer to AST node `T` with reference type `R`
6  * specialization: strong pointer `ast::ptr<T>` is used for an ownership relationship
7  * specialization: weak pointer `ast::readonly<T>` is used for an observation relationship
8  * added `ast::ptr_base<T,R>::as<S>()` with same semantics as `dynamic_cast<S*>(p)`
9
10## Visitors ##
11* `Visitor` and `Mutator` are combined into a single `ast::Visitor` class
12  * Base nodes now override `Node* accept( Visitor& v ) = 0` with, e.g. `Stmt* accept( Visitor& v ) override = 0`
13* `PassVisitor` is replaced with `ast::Pass`
14
15## Structural Changes ##
16`CodeLocation` has been devolved from `BaseSyntaxNode` to `ast::ParseNode`
17* excludes `ast::Type` from carrying location information
18* `CodeLocation` is a mandatory constructor field for `ast::ParseNode`
19  * all subclass constructors must fill it; by convention, from their first argument
20
21`N->print(std::ostream&)` is a visitor now, port these methods to `ast::Print` class
22* **TODO** write this visitor
23* **TODO** write `std::ostream& operator<< ( std::ostream& out, const Node* node )` in `Node.hpp` in terms of `ast::Print`
24* `Declaration::printShort` should also be integrated
25
26`clone` is private to `Node` now
27* still needs to be overriden to return appropriate type
28  * e.g. `private: virtual Stmt* clone() const override = 0;`
29
30All leaves of the `Node` inheritance tree are now declared `final`
31* e.g. `class CompoundStmt final : public Stmt`
32* allows compiler to optimize virtual calls to static calls if given static type
33
34Pulled `FuncSpecifiers` and `StorageClasses` out of `Type` into their own headers
35* Made `BFCommon` a `MakeBitfield` macro in its own header
36  * added default and field-init constructors to macro
37
38Prefer move semantics for containers passed to node constructors
39
40## Code Style ##
41
42### Files ###
43* Headers have a `.hpp` suffix
44* Source code has a `.cpp` suffix
45* All source has the project-standard leading and trailing comments
46* prefer `#pragma once` over `#ifdef` guards
47* namespaces that cover entire files don't get indented
48
49### Documentation ###
50* class, method, and field comments should use doxygen-style `///` prefix
51  * should be included on all classes
52  * should be included on any method declaration that doesn't have an obvious behaviour from either naming convention (e.g. constructor, print operator, implement visitor pattern) or an inline implementation
53* use explanatory comments with `//` wherever appropriate
54  * older comments should be maintained in porting process wherever possible
55
56### Naming ###
57* Preserve names from previous AST whenever reasonable, and get team consensus on any changes.
58* Strong justification required for private fields
59  * No `get_` prefix on getters (including for generated fields)
60    * exception is `DeclWithType::get_type()`
61* Notable changes:
62  * for concision and consistency with subclasses:
63    * `Declaration` => `ast::Decl`
64        * `DeclarationWithType` => `ast::DeclWithType`
65        * `Expression` => `ast::Expr`
66        * `Initializer` => `ast::Init`
67    * `Statement` => `ast::Stmt`
68  * because they don't really belong to `Type` (and for consistency with `Linkage::Spec`):
69    * `Type::StorageClasses` => `ast::Storage::Classes`
70          * `Type::Extern` etc. => `ast::Storage::Extern` etc.
71        * `LinkageSpec::Spec` => `ast::Linkage::Spec`
72          * `LinkageSpec::Mangle` etc. => `ast::Linkage::Mangle` etc.
73          * `LinkageSpec::linkageUpdate` => `ast::Linkage::update`
74          * `LinkageSpec::linkageName` => `ast::Linkage::name`
75          * `LinkageSpec::isMangled(Spec)` etc. => `Spec.is_mangled` etc.
76          * `LinkageSpec::Intrinsic` etc. => `ast::Linkage::Intrinsic` etc.
77
78## Specific Nodes ##
79`Decl`
80* `storageClasses` => `storage`
81* `declFromId()` => `fromId()`
82  * not 100% sure about the return type here...
83
84`DeclWithType`
85* When `SymTab::Validate::Pass2` is rewritten, update comment on `mangleName` with new name of pass
86* `get_scopedMangleName()` => `scopedMangleName()`
87* `get_type()` now returns `const Type*` so can't be inadvertently mutated
88  * still with `get_` name so it doesn't conflict with subclass field names
89
90`ObjectDecl`
91* changed constructor parameter order for better defaults
92  * allows `newObject` as just default settings
93
94`TypeDecl`
95* stripped `isComplete()` accessor in favour of direct access to `sized`
96
97`EnumDecl`
98* **TODO** rebuild `eval` for new AST (re: `valueOf` implementation)
99
100`Expr`
101* Merged `inferParams`/`resnSlots` into union, as suggested by comment in old version
102  * does imply get_/set_ API, and some care about moving backward
103
104`Label`
105* `get_statement()` exclusively used for code location, replaced with `CodeLocation` field
106
107`CompoundStmt`
108* **TODO** port copy operator
109  * Needs to be an almost-shallow clone, where the declarations are cloned only if needed
110  * **TODO** port DeclReplacer
111* Still a `std::list` for children, rather than `std::vector`
112  * allows more-efficient splicing for purposes of later code generation
113
114`Type`
115* `forall` field split off into `ParameterizedType` subclass
116  * any type that needs it can inherit from `ParameterizedType`
117* `get_qualifiers()` replaced with accessor `qualifiers()` and mutator `set_qualifiers()`
118  * `get_CV()` replaced with `is_CV()` variants
119* A number of features only supported on aggregates pushed down to `ReferenceToType`:
120  * `attributes`: per docs [1] GCC only supports type attributes on aggregates and typedefs
121    * suggest adding a `TypeWithAttributes` wrapper type if this proves insufficient
122  * `getAggr()`
123  * `genericSubstitution()`
124
125`BasicType`
126* does not inherit from `Type` to allow pointer inlining
127* moved `Kind` before qualifiers in constructor to allow for default
128* **TODO** move `kind`, `typeNames` into code generator
129
130[1] https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Type-Attributes.html#Type-Attributes
131
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