RPC-Lang

A simple, toy programming language and compiler created using LLVM

Requirements

• LLVM version 16 or later. I installed using the shell script on https://apt.llvm.org/ which made it very easy
• A C++ compiler. I used g++ though I'm sure clang++ would work too.

Features

• 3 primitive types: 32 bit integer, 64 bit float (double), character (8 bit integer)
  • Implicit casting between types
• Arrays of primitive types, capable of supporting an arbitrary number of dimensions
• Global and local variables
• Control flow
  • For loops
  • While loops
  • If/else statements
• Functions
• Support for all major arithmetic and logical operators
• I/O using existing C++ functions
• And more!

Syntax

Single line comments are declared with $

Declaring Variables

To declare a variable, use the ‘var’ keyword, followed by a type and identifier. Primitive variables must be initialized with a value, while arrays cannot be initialized with a value. The size of an array must also be declared with an integer literal value, as all arrays are stack allocated.

…
var i32 integer <- 0;
var f64 double <- 0.0;
var ch8 character <- '0';
…

var i32 x;  $ error

…
var i32[5] integer;
integer <- {1 2 3};

var f64[4] double;
double <- {1.0 2.5};

var ch8[3] character;
character <- {'a' 'b'};
…

var i32 x <- {1 2 3};  $ error

Character arrays can also be initialized with double quotes like in C, to automatically append a null character to the end of the array.

…
var ch8[3] character;
character <- "Hi";
…

When initializing an array with braces, values in the bracket must be literals of the same type, meaning no variables. This is also one of the only situations where primitive types will not be implicitly casted.

var f64[4] double;
double <- {1.0 2};  $ Error, 2 is an i32

Control Flow

All control flow statements must have braces, even if there is only 1 statement in the loop.

For Loops

For loops are defined similar to any C-like language:

for (var i32 i <- 0; i < 10; i <- i + 1) {
  $ stuff
}

While Loops

While loops run as long as the condition holds true. 1 = true while 0 = false. Logical operators can also be used to evaluate conditions.

while (1) { $ same as while (true) in C++
  $ stuff
}

If Statements

If statements act like those in any other language, except instead of else statements, I made it "otherwise" statements, which are optional

var i32 bool <- 0;
if (bool) {
  $ stuff
} otherwise {
  $ other stuff
}

Functions

Functions can either be declared or defined. Declared functions can be defined later, or defined in a separate translation unit. The benefit of this is that a function can be declared, and then defined in C++. This is what allows for I/O functions to be used.

Declaring a function

func f() i32;

Defining a function

def func f() i32 {
  $ body
}

In the parenthesis, function parameters can be listed. The type after the parenthesis is the return type. A return type can exist in an if statement, but the language is not sophisticated enough to detect return expressions within a statement. This means that a return value must be specified in the main body.

def func f(i32 x) i32 {
  if (x > 5) {
    return 5;
  } otherwise {
    return -1
  }
  return -1; $ required, if not Error: No return type will be posted
}

A function can also return void. A return expression is not required in this case, but if you do wish to return, you may use "return void;"

def func f() void {
  $ body
  $ optionally:
  return void;
}

Operators

There are two types of operators, arithmetic and logical.

Arithmetic

• + and -
• * and /

Logical

• > and <
• >= and <=
• "and"
• "or"
• =
• "not"
  "not" works as follows

if (not 1 = 2) {
  $ will enter
}

Compilation

The compiler can be compiled using the makefile, specifically rule "make rpc".
To generate an output file from a text source file, run

./rpc <input_name>.txt

Or optionally

./rpc <input_name>.txt -ir

To print the LLVM IR for the input.

As I did not make a linker, an external linker must be used to generate an executable from a source text file. Furthermore, if you use any of the I/O functions from standard_lib.txt/cpp, you need to link using a C++ compiler, compiling and linking standard_lib.cpp. So, to compile a source text file, run the compiler executable as follows:

g++ <output_name>.o standard_lib.cpp <g++ args>

Or leave off standard_lip.cpp if you wish to have no I/O.

Bugs

While I tried to test as much as I could, I surely missed some bugs. If you find any, please let me know by means of an issue.
There are also some memory leaks present, though only in main-loop.cpp in generate_output_file. This code was taken from the LLVM website where they outlined how to generate an output file, so to my understanding these leaks are not a fault of my own code.