mirror of
https://github.com/nasa/trick.git
synced 2024-12-30 01:48:52 +00:00
110 lines
4.8 KiB
Plaintext
110 lines
4.8 KiB
Plaintext
/**
|
|
|
|
@page LEVEL2 Interface Code Generator Design
|
|
|
|
The Interface Code Generator (ICG) creates class/struct layout information, called
|
|
attributes, used to convert string variable names to simulation memory
|
|
addresses. The attributes are used with several of Trick's services
|
|
including checkpointing, data recording, and the variable server.
|
|
|
|
ICG execution is divided into 2 parts.
|
|
|
|
-# Executing the Clang C++ frontend to parse all header files and extract
|
|
class/struct information.
|
|
-# Print class/struct information as attributes in input/output source code.
|
|
|
|
@section LEVEL3 Clang C++ Frontend
|
|
|
|
ICG uses the Clang frontend. Clang is a C/C++ frontend to the LLVM compiler.
|
|
Clang and LLVM provide libraries that allow developers to create their own tools
|
|
using the compiler. ICG calls the clang parser to process the header
|
|
files and converts the source text into a tree form called an abstract syntax tree
|
|
(AST). Clang completely handles all textual parsing. ICG provides classes to
|
|
provide input parameters to the compiler and to extract the information out of the
|
|
AST.
|
|
|
|
@section LEVEL4 Parser Setup
|
|
|
|
The frontend has some parameters that must be set in order for the parser to
|
|
execute.
|
|
|
|
@section LEVEL5 Parsing Language
|
|
|
|
The S_source.hh file where parsing begins is written in C++. The frontend is set to
|
|
parse C++.
|
|
|
|
@section LEVEL5 Target Architecture
|
|
|
|
The frontend requires a target architecture set. ICG does not pass the AST to the
|
|
next stage of compiler tools after the frontend, so it doesn't matter what the
|
|
target architecture is set to. Setting the target to the the default architecture
|
|
works.
|
|
|
|
@section LEVEL4 Preprocessor
|
|
|
|
The frontend includes a preprocessor. The preprocessor handles include and define
|
|
statements. ICG provides a pair of classes that interact with the clang preprocesor.
|
|
The HeaderSearchDirs class to provide the preprocessor with include search
|
|
directories and default defines. The CommentSaver class saves all comments parsed
|
|
by the preprocessor. These classes are used throughout the rest of ICG execution.
|
|
|
|
@section LEVEL5 HeaderSearchDirs
|
|
|
|
The HeaderSearchDirs manages the header search directories used by the preprocessor
|
|
and provides an interface for querying the inclusion status of a directory. Since
|
|
this class is closely related to the preprocessor, it also handles define macros.
|
|
|
|
The HeaderSearchDirs class provides a list of include search directories to the
|
|
clang preprocessor. There are two types of include directories, system include
|
|
directories and user provided directories. Both types must be supplied to the
|
|
preprocessor.
|
|
|
|
The system include directories are retrieved by running the TRICK_CPPC compiler
|
|
in verbose preprocessor mode with no input code. When the compiler is run
|
|
in this mode, it prints the system include directories built into the compiler.
|
|
This class parses that output for the system include directories and feeds the
|
|
list into the preprocessor.
|
|
|
|
The user include directories are retrieved from the command line when executing
|
|
ICG. Typically ICG is called with the TRICK_CXXFLAGS environment variable
|
|
included as an argument. TRICK_CXXFLAGS may include -I<include_dir> strings.
|
|
These include directories are parsed from the command line and fed to the
|
|
preprocessor.
|
|
|
|
This class parses the TRICK_ICG_EXCLUDE environment variable and manages a list
|
|
of directories ICG should not write any output source code.
|
|
|
|
The HeaderSearchDirs class provides boolean responses to questions to whether a
|
|
path is in a user directory or is in an TRICK_ICG_EXCLUDE directory.
|
|
|
|
@section LEVEL5 CommentSaver
|
|
|
|
The CommentSaver class saves comments found in user code and provides an iterface
|
|
for retrieving comments based on file name/line number. The class also provides
|
|
an interface to retrieving several fields from a Trick header comment including
|
|
the ICG and ICG_EXCLUDE_TYPES fields.
|
|
|
|
The clang preprocessor includes a comment handler interface. ICG uses
|
|
this interface to attach the CommentSaver class. Each comment handled by this
|
|
class is stored in a map indexed by file name and line number.
|
|
|
|
@section LEVEL4 Abstract Syntax Tree (AST) Traversal
|
|
|
|
Traversing the resulting AST is bulk of ICG's work. The clang compiler provides
|
|
an interface allowing ICG to attach handlers to process interesting events during
|
|
code parsing. In this case, ICG only attaches a handler when clang is finished
|
|
parsing the entire input file, called HandleTranslationUnit.
|
|
|
|
When HandleTranslationUnit is start parsing the AST searching for top level
|
|
declarations we want to process. From the top level recursively calls
|
|
tree parsers that specialize in extracting information about typedefs,
|
|
classes and structs, fields within each class/struct, and enumerations.
|
|
|
|
The following diagram shows the recursive class instantiation sequence as well
|
|
as the data returned to the caller.
|
|
|
|
@section LEVEL3 Writing Class/Struct Attributes
|
|
|
|
*/
|
|
|