How to run

Pre-requisites

antlr4 python runtime

pip install antlr4-python3-runtime

Optional - (For Formatting Rust)

rustup component add rustfmt
# if not installed please comment the line
# os.system("rustfmt " + output_filename) in main.py

Running the Program

Generating Lexer and Parser using anltr4 in Python inside "dist" directory

antlr4 -Dlanguage=Python3 CPP14Lexer.g4 -visitor -o dist
antlr4 -Dlanguage=Python3 CPP14Parser.g4 -visitor -o dist

Execution

python main.py filename

This will create file named filename_converted.rs and filename_tree.tree in the same directory as the input file.

Support for C Constructs:

Supported Constructs and their limitations:

• main function

  • needs care to ignore the return 0; if present
  • code snippets that use argc and argv are not dealt with. as the way to access cli arguments in rust is a bit different

• declaration and initialization of single dimensional arrays.

• declaration and initialization of multi-dimensional arrays

• declaration of simple datatypes and implicit as well as explicit casting.

• functions

  • regular functions are supported
  • function pointers are not supported

• while loops

  • issues with statements like while (1) as rust expects boolean values explicitly

• for loops

  • handled by unwrapping to a while loop

• conditional statement

  • issues with statements like if (5) as rust expects boolean values explicitly

• switch statement

• printf

• structs

  • structs can support all primitive data types.

• enums

• arrays

• pointers

  • partially converted into raw pointers, will require manual intervention to correct the transpiled code

Unsupported Constructs:

• Pointers . Raw pointers can be declared and used to point to variables but they cannot be dereferenced. Smart pointers or references can be used but they are based on the principle: there can be at most one mutable reference to data. in c, multiple pointers to same position and can modify it.

• scanf . in constrast to how easy it is to handle printf. the way of taking input in rust is cumbersome. always checking the input is trimmed and correctly parsed before assigning to a target and handling any exceptions during parsing as well.

• strings . strings are character arrays in c. functions like strlen, strcpy, have corresponding functions in rust. but need a strategy to follow. better to make a corresponding character array in rust or make a string in rust (strings come with ownership issues)

• header files . So far the header files have been ignored by the grammar. so might need to modify the grammar.

• Advanced constructs

  • Macros
  • preprocessor directives
  • function pointers?
  • pointers to pointers?
  • pointer to arrays?

Support for C++ Constructs

Supported constructs and their limitations

• cout

• Stl containers : Vectors, stacks, queues, sets and maps

  • Implemented using a rust struct which acts as a wrapper over rust's equivalent containers
  • Doesn't implement iterators

• Classes

  • Constructors are converted into a function returning a struct. So transpiled constructors require manual rewriting
  • inheritance is not supported
  • operator overloading is supported for arithmetic operators

• Templates

  • using templates to support multiple datatypes is supported

• CPP Strings

  • Implemented using a rust struct which acts as a wrapper over rust's Strings
  • doesn't implement iterators

Unsupported constructs

• exceptions
• NULL values : This requires conversion of NULL values to Options in rust, but since it requires lots of changes in logic as well, NULL values aren't supported
• function overloading
• default values for parameters
• safe and unsafe Pointers
  • Can be implemented using a rust wrapper struct
• cin : similar to scanf
• Iterators
• Range based for loops
  • Issue due to lack of support for iterators
• new statements