MyC Compiler Sample

Sample Overview

The goal of the MyC compiler is to show the implementation of various features of the CLI.

The following table shows the command-line options for this sample.

Option	Description
/debug	Generates debug information.
/nodebug	Prevents generation of debug information.
/list	Generates an assembly listing (.asm).
/dll	Creates a DLL assembly.
/exe	Creates an executable assembly.
/outdir:path	Creates output files in the current directory.

Architecture Diagram

MyC Language Specification

Goals

The goal of the MYC compiler is to show common intermediate language (CIL) instructions and the CLI in action.

Overview

The compiler itself is a simple recursive descent parser with a single pass code generator. It generates an assembler source file which is then used as input to the IL Assembler.

Language Specification

The language is a subset of the C language with simplified declarations, both external and local.

Data Types

The only supported data types are int and void. Limiting these choices allows a simpler sample compiler design.

Data Declaration

Variables can be declared static or local. Implicit static declarations occur outside of function declarations. Local declarations can occur only at the beginnings of functions prior to statements.

For example:

int func1()
  {
  int y;
  }
int x;

int func2()
  {
  static int z;
  };

In this example the variable x is a static declaration (by default) and the variable y is a local variable in function func1(). The variable z is actually a static, even though it is declared within a function.

Flow Control

if-else blocks
while loops
for loops

Restrictions

Integer data
Outer declarations only
Static methods and function calls only

Backus-Naur Definition

letter ::= "A-Za-z";
digit ::= "0-9";

name ::= letter { letter | digit };
integer ::= digit { digit };

ident ::= name | function_call;
function_call ::= name "(" [expr {, expr}] ")";

factor ::= (ident | integer | "(" expr ")" );
unary_factor ::= ["+"|"-"] factor;

term1 ::= ["*"|"/"] factor;
term0 ::= factor { term1 };
first_term ::= unary_factor term1;

math_expr ::= first_term { ["+"|"-"] term0 }
rel_expr ::= math_expr ("=="|"!="|"<"|">"|">="|"<=") math_expr;
not_factor ::= ["!"] rel_expr;
term_bool ::= not_factor { ("&" | "&&") not_factor };
bool_expr ::= term_bool { ("|" | "^") term_bool };
expr ::= bool_expr;

assign = ident "=" expr;
assign_stmt ::= assign ";" ;
if_stmt ::= "if" "(" expr ")" stmt_block [ "else" inner_block ];
while_stmt ::= "while" "(" expr ")" inner_block;
for_stmt ::= "for" "(" assign ";" expr ";" assign ")" inner_block
break_stmt ::= "break" ";";
cont_stmt ::= "continue" ";";
ret_stmt ::= "return" expr ";";
stmt ::= (
if_stmt
| while_stmt
| for_stmt
| break_stmt
| cont_stmt
| ret_stmt
| assign_stmt
);
inner_block ::= "{" { stmt } "}";
outer_block ::= "{" { inner_decl } { stmt } "}";

inner_decl ::= [ class ] type ident { "," ident } ";";

class ::= "extern" | "static" | "auto";
type ::= "int" | "void";

params ::= type ident { , type ident };
outer_decl ::= [ class ] type ident { "," ident } ";";
func_decl ::= [ class ] type ident "(" params ")" outer_block;

Sample Source and Build Output Locations

The sample source is found in sscli\samples\compilers\myc\src directory. The source files are:

The build output location is %TARGETCOMPLUS%\samples\compilers\myc. The output file is an executable assembly named myc.exe.

Building the Sample

All samples are built from the buildall script.

You can also build all the samples by switching to the root of the sample directory, sscli\samples, and typing build -c.

You can build this specific sample by switching to the sample directory and typing build -c.

Running the Sample

Because the MyC language does not support referencing external assemblies, use the Runtime Debugger to step through test applications built using MyC.

Run env.bat or source the env.csh or env.sh script files depending on your platform.
Build the SSCLI using the buildall script or batch file.
Switch to the %TARGETCOMPLUS%\samples\compilers\myc directory.
Type the following command:

clix myc /debug inputfile

where inputfile is the name of a MyC source file. For example:

clix myc /debug tflow.myc
Debug the resulting assembly:

cordbg tflow.exe

Known Issues

The debug line number count is off by 1.

References

Modern Compiler Implementation in C, by Andrew W Appel.
Algorithms in C++ by Robert Sedgewick.
Advanced Compiler Design and Implementations, by Steven S Muchnick.
Compiler Construction, by Niklaus Wirth.
Principles of Compiler Design, by Alfred V. Aho and and Jeffrey D. Ullman.