carefully designed as the following components:
libsupport - Basic support library, reused from LLVM.
+
libsystem - System abstraction library, reused from LLVM.
libbasic - Diagnostics, SourceLocations, SourceBuffer abstraction,
file system caching for input source files. This depends on
libsupport and libsystem.
+
libast - Provides classes to represent the C AST, the C type system,
builtin functions, and various helpers for analyzing and
manipulating the AST (visitors, pretty printers, etc). This
library depends on libbasic.
-
+
+
liblex - C/C++/ObjC lexing and preprocessing, identifier hash table,
pragma handling, tokens, and macros. This depends on libbasic.
+
libparse - C (for now) parsing and local semantic analysis. This library
invokes coarse-grained 'Actions' provided by the client to do
stuff (e.g. libsema builds ASTs). This depends on liblex.
+
libsema - Provides a set of parser actions to build a standardized AST
for programs. AST's are 'streamed' out a top-level declaration
at a time, allowing clients to use decl-at-a-time processing,
build up entire translation units, or even build 'whole
program' ASTs depending on how they use the APIs. This depends
on libast and libparse.
-
+
+ librewrite - Fast, scalable rewriting of source code. This operates on
+ the raw syntactic text of source code, allowing a client
+ to insert and delete text in very large source files using
+ the same source location information embedded in ASTs. This
+ is intended to be a low-level API that is useful for
+ higher-level clients and libraries such as code refactoring.
+
+ libanalysis - Source-level dataflow analysis useful for performing analyses
+ such as computing live variables. It also includes a
+ path-sensitive "graph-reachability" engine for writing
+ analyses that reason about different possible paths of
+ execution through source code. This is currently being
+ employed to write a set of checks for finding bugs in software.
+
libcodegen - Lower the AST to LLVM IR for optimization & codegen. Depends
on libast.
+
clang - An example driver, client of the libraries at various levels.
This depends on all these libraries, and on LLVM VMCore.
- This front-end has been intentionally built as a DAG, making it easy to
- reuse individual parts or replace pieces if desired. For example, to build a
- preprocessor, you take the Basic and Lexer libraries. If you want an indexer,
- you take those plus the Parser library and provide some actions for indexing.
- If you want a refactoring, static analysis, or source-to-source compiler tool,
- it makes sense to take those plus the AST building and semantic analyzer
- library. Finally, if you want to use this with the LLVM backend, you'd take
- these components plus the AST to LLVM lowering code.
+ This front-end has been intentionally built as a DAG of libraries, making it
+ easy to reuse individual parts or replace pieces if desired. For example, to
+ build a preprocessor, you take the Basic and Lexer libraries. If you want an
+ indexer, you take those plus the Parser library and provide some actions for
+ indexing. If you want a refactoring, static analysis, or source-to-source
+ compiler tool, it makes sense to take those plus the AST building and semantic
+ analyzer library. Finally, if you want to use this with the LLVM backend,
+ you'd take these components plus the AST to LLVM lowering code.
In the future I hope this toolkit will grow to include new and interesting
components, including a C++ front-end, ObjC support, and a whole lot of other
- To make diagnostics more gcc-like: -fno-caret-diagnostics -fno-show-column
- Enable metric printing: -stats
- * -fsyntax-only is the default mode.
-
- * -E mode gives output nearly identical to GCC, though not all bugs in
- whitespace calculation have been emulated (e.g. the number of blank lines
- emitted).
+ * -fsyntax-only is currently the default mode.
- * -fsyntax-only is currently partially implemented, lacking some semantic
- analysis.
+ * -E mode works the same way as GCC.
- * -Eonly mode does all preprocessing, but does not print the output, useful for
- timing the preprocessor.
+ * -Eonly mode does all preprocessing, but does not print the output,
+ useful for timing the preprocessor.
- * -parse-print-callbacks prints almost no callbacks so far.
+ * -fsyntax-only is currently partially implemented, lacking some
+ semantic analysis (some errors and warnings are not produced).
+
+ * -parse-noop parses code without building an AST. This is useful
+ for timing the cost of the parser without including AST building
+ time.
- * -parse-ast builds ASTs, but doesn't print them. This is most useful for
- timing AST building vs -parse-noop.
+ * -parse-ast builds ASTs, but doesn't print them. This is most
+ useful for timing AST building vs -parse-noop.
- * -parse-ast-print prints most expression and statements nodes, but some
- minor things are missing.
+ * -parse-ast-print pretty prints most expression and statements nodes.
+
+ * -parse-ast-check checks that diagnostic messages that are expected
+ are reported and that those which are reported are expected.
+
+ * -dump-cfg builds ASTs and then CFGs. CFGs are then pretty-printed.
+
+ * -view-cfg builds ASTs and then CFGs. CFGs are then visualized by
+ invoking Graphviz.
+
+ For more information on getting Graphviz to work with clang/LLVM,
+ see: http://llvm.org/docs/ProgrammersManual.html#ViewGraph
- * -parse-ast-check checks that diagnostic messages that are expected are
- reported and that those which are reported are expected.
III. Current advantages over GCC:
* Fast #import with a module system.
* Dependency tracking: change to header file doesn't recompile every function
that texually depends on it: recompile only those functions that need it.
+ This is aka 'incremental parsing'.
IV. Missing Functionality / Improvements
clang driver:
- * Include search paths are hard-coded into the driver.
+ * Include search paths are hard-coded into the driver. Doh.
File Manager:
- * Reduce syscalls, see NOTES.txt.
+ * Reduce syscalls for reduced compile time, see NOTES.txt.
Lexer:
* Source character mapping. GCC supports ASCII and UTF-8.
* Add support for -M*
Traditional Preprocessor:
- * All.
+ * Currently, we have none. :)
Parser:
* C90/K&R modes are only partially implemented.
- * __extension__, __attribute__ [currently just skipped and ignored].
- * "initializers", GCC inline asm.
+ * __extension__ is currently just skipped and ignored.
Semantic Analysis:
- * Perhaps 75% done.
-
-Code Gen:
- * Mostly missing.
+ * Perhaps 85% done.
+LLVM Code Gen:
+ * Most of the easy stuff is done, probably 65.42% done so far.
projects / clang / blobdiff