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160 lines
5.4 KiB
Markdown
160 lines
5.4 KiB
Markdown
# gencpp
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An attempt at simple staged metaprogramming for C/C++. Reflect and generate code for your codebase at runtime!
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The library API is a composition of code element constructors, and a non-standards-compliant single-pass C/C++ parser.
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These build up a code AST to then serialize with a file builder, or can be traversed for staged-reflection of C/C++ code.
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This code base attempts follow the [handmade philosophy](https://handmade.network/manifesto).
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Its not meant to be a black box metaprogramming utility, it should be easy to integrate into a user's project domain.
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## Documentation
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* [docs - General](./docs/Readme.md): Overview and additional docs
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* [AST_Design](./docs/AST_Design.md): Overview of ASTs
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* [AST Types](./docs/AST_Types.md): Listing of all AST types along with their Code type interface.
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* [Parsing](./docs/Parsing.md): Overview of the parsing interface.
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* [Parser Algo](./docs/Parser_Algo.md): In-depth breakdown of the parser's implementation.
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* [base](./base/Readme.md): Essential (base) library.
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* [gen_c_library](./gen_c_library/): C11 library variant generation (single header and segmented).
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* [gen_segmented](./gen_segmented/): Segmented C++ (`gen.<hpp/cpp>`, `gen.dep.<hpp/cpp>`) generation
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* [gen_singleheader](./gen_singleheader/): Singlehader C++ generation `gen.hpp`
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* [gen_unreal_engine](./gen_unreal_engine/): Unreal Engine thirdparty code generation.
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## Notes
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This project is still in development (very much an alpha state), so expect bugs and missing features.
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See [issues](https://github.com/Ed94/gencpp/issues) for a list of known bugs or todos.
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The library can already be used to generate code just fine, but the parser is where the most work is needed. If your C++ isn't "down to earth" expect issues.
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A `natvis` and `natstepfilter` are provided in the scripts directory (its outdated, I'll update this readme when its not).
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*Minor update: I've been using [RAD Debugger](https://github.com/EpicGamesExt/raddebugger) with this and the code structures should be easy to debug even without natvis.*
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## Usage
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A metaprogram is built to generate files before the main program is built. We'll term runtime for this program as `GEN_TIME`. The metaprogram's core implementation are within `gen.hpp` and `gen.cpp` in the project directory.
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`gen.cpp` \`s `main()` is defined as `gen_main()` which the user will have to define once for their program. There they may reflect and/or generate code.
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In order to keep the locality of this code within the same files the following pattern may be used (although this pattern isn't the best to use):
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Within `program.cpp` :
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```cpp
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#ifdef GEN_TIME
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#include "gen.hpp"
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...
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u32 gen_main()
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{
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gen::Context ctx;
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gen::init(& ctx);
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...
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gen::deinit(& ctx);
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return 0;
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}
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#endif
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// "Stage" agnostic code.
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#ifndef GEN_TIME
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#include "program.gen.cpp"
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// Regular runtime dependent on the generated code here.
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#endif
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```
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The design uses a constructive builder API for the code to generate.
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The user is provided `Code` objects that are used to build up the AST.
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Example using each construction interface:
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### Upfront
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Validation and construction through a functional interface.
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```cpp
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Code t_uw = def_type( name(usize) );
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Code t_allocator = def_type( name(allocator) );
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Code t_string_const = def_type( name(char), def_specifiers( args( ESpecifier::Const, ESpecifier::Ptr ) ));
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Code header;
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{
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Code num = def_variable( t_uw, name(Num) );
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Code cap = def_variable( t_uw, name(Capacity) );
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Code mem_alloc = def_variable( t_allocator, name(Allocator) );
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Code body = def_struct_body( args( num, cap, mem_alloc ) );
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header = def_struct( name(ArrayHeader), __, __, body );
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}
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```
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### Parse
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Validation through ast construction.
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```cpp
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Code header = parse_struct( code(
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struct ArrayHeader
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{
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usize Num;
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usize Capacity;
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allocator Allocator;
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};
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));
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```
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### Untyped
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No validation, just glorified text injection.
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```cpp
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Code header = code_str(
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struct ArrayHeader
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{
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usize Num;
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usize Capacity;
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allocator Allocator;
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};
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);
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```
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`name` is a helper macro for providing a string literal with its size, intended for the name parameter of functions.
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`code` is a helper macro for providing a string literal with its size, but intended for code string parameters.
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`args` is a helper macro for providing the number of arguments to varadic constructors.
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`code_str` is a helper macro for writing `untyped_str( code( <content> ))`
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All three construction interfaces will generate the following C code:
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```cpp
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struct ArrayHeader
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{
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usize Num;
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usize Capacity;
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allocator Allocator;
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};
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```
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**Note: The formatting shown here is not how it will look. For your desired formatting its recommended to run a pass through the files with an auto-formatter.**
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*(The library currently uses clang-format for formatting, beware its pretty slow...)*
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## Building
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See the [scripts directory](scripts/).
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## Gallery
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### Listing definitions in the Cuik Compiler
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https://github.com/user-attachments/assets/2302240c-01f1-4e1b-a4b5-292eb3186648
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### Unreal: Generating a UAttributeSet from a UDataTable
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https://github.com/user-attachments/assets/2a07b743-825d-4f9f-beaf-3559e8748a4d
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