Compiler

All of the functionality mentioned in the past chapters describing each stage of the compilation process and their respective components are all combined in a Compiler object which adds additional functionality via the compiler configuration sub-system. This sub-system is passed into each stage (TODO: Not yet, only the code emitter, we must fix this) such that if a requirement for a decision to be taken based on compiler flags is specified then such configuration paremeters can be obtained via each module of the compilation stage.

Compiler system

The Compiler class provides is constructed by being given source code as a string along with a File struct which represents the file of which to write the final emitted code to. This type provides the following methods:

1. this(string sourceCode, File emitOutFile)
   • Constructs a new compiler object with the given source code and the file to write the emitted code out to
   • An newly initialized File struct that doesn’t contain a valid file handle can be passed in in the case whereby the emitter won’t be used but an instance of the compiler is required
2. doLex()
   • Performs the tokenization of the input source code, sourceCode.
   • A LexerException may be thrown if an error occurs during the toeknization process.
3. getTokens()
   • Returns the tokens produced by a call to doLex()
   • A CompilerException will be thrown if called without doLex() having been called.
4. doParse()
   • Peforms parsing on the tokens and returns the generated super-container parse node, Module.
   • A CompilerException will be thrown if called without doLex() having been called.
   • A CompilerException will be thrown if called without and no tokens were produced by the call to doLex().
5. doTypeCheck()
   • Performs typechecking and code generation.
   • A CompilerException will be thrown is the previous stages, including doParse() and its requirements, have not been called.
6. doEmit()
   • Performs emitting of C code
   • A CompilerException will be thrown is the previous stages, including doTypeCheck() and its requirements, have not been called.
7. compile()
   • Performs all of the above stages.
   • A CompilerException can be thrown for any of the aforementioned reasons.

TODO: Document CompilerException exception and CompilerError enum.

Configuration sub-system

At user-request or due to constraints of the host machine it may be required that certain aspects of the various components of the compiler be modified in terms of their behaviour. This is where the compiler configuration sub-system comes in in order to support a key-value store that can be used via the compiler.config field at any time.

The CompilerConfiguration API

The CompilerConfiguration exposes the following API:

1. bool hasConfig(string key)
   • Checks if the given key exists in the key-value store, returns false if not, true otherwise
2. addConfig(ConfigEntry entry)
   • Stores the given entry in the cnfiguration store
   • Throws a CompilerException if you are trying to update an entry to a different tye than the existing one
3. ConfigEntry getConfig(string key)
   • Returns the ConfigEntry at the provided name
   • Throws a CompilerException if no such entry exists
4. CompilerConfiguration defaultConfig()
   • Returns the default compiler configuration (TODO: link to it)

The ConfigEntry API

The ConfigEntry represents a configuration entry, this is composed of:

1. An entry name
   • Fetched via string getName()
2. An entry type
   • This is fetched via ConfigType getType()
3. An entry value
   • This is fetched via getX()
   • There are several getter functions which will interpret the union space dependent on which one you call, however, in reality a misinterpretation will cause a runtime error as we catch it before you attempt to do a reinterpattion of it, therefore throwing a CompilerException

The types that can be stored and their respectives methods are:

1. Boolean
   • Values: true or false
   • Use getBoolean()
2. Number
   • Values: A valid D ulong
   • Use getNumber()
3. Text
   • Values: A D string
   • Use getText()
4. Tex array
   • Values: A D string[]
   • Use getArray()

Example usage

Creation of entries

Below is an example of the usage of the ConfigEntrys in the CompilerConfiguration system, here we add a few entries:

/* Enable Behaviour-C fixes */
config.addConfig(ConfigEntry("behavec:preinline_args", true));

/* Enable pretty code generation for DGen */
config.addConfig(ConfigEntry("dgen:pretty_code", true));

/* Enable entry point test generation for DGen */
config.addConfig(ConfigEntry("dgen:emit_entrypoint_test", true));

/* Set the mapping to hashing of entity names (TODO: This should be changed before release) */
config.addConfig(ConfigEntry("emit:mapper", "hashmapper"));

Retrieval of entries

Later on we can retrieve these entries, the below is code from the DGen class which emits the C code), here we check for any object files that should be linked in:

//NOTE: Change to system compiler (maybe, we need to choose a good C compiler)
string[] compileArgs = ["clang", "-o", "tlang.out", file.name()];

// Check for object files to be linked in
string[] objectFilesLink;
if(config.hasConfig("linker:link_files"))
{
    objectFilesLink = config.getConfig("linker:link_files").getArray();
    gprintln("Object files to be linked in: "~to!(string)(objectFilesLink));
}
else
{
    gprintln("No files to link in");
}

Pid ccPID = spawnProcess(compileArgs~objectFilesLink);