Nesc-internals

Driver Scripts

• ncc: driver script for TinyOS, understands TinyOS platforms, etc. Behaves like gcc with extra options. Main task is to generate and execute a nescc command

• nescc: driver script for nesC, understands how to compile a nesC application. Supports cross-compilation. Behaves like gcc with extra options. Main task is to generate and execute a gcc command with the appropriate magic (see the tdspecs file) to invoke nesc-compile on .nc files.

• mig, nescc-mig: TinyOS and non-TinyOS scripts to invoke the message interface generator. End up calling nescc with the "right" options.

• ncg, nescc-ncg: TinyOS and non-TinyOS scripts to invoke the constant generator. End up calling nescc with the "right" options.

Internal Script

• nesc-compile: Invoked by gcc when passed a .nc file. Must generate a .s or .o file depending on options received. Essentially, invokes nesc1 to transform nesC application into a C file, then invokes gcc to compile this C file.

In all these scripts, gcc stands for the target platform's gcc, though, except for the invocation from nesc-compile, this isn't typically crucial.

nesc1

Overview: takes a "root" .nc file and generates a C file representing the whole nesC application. Also has a few other paths, to generate information for mig, TinyOS 1.x doc info (legacy only, the 2.x docs use the XML output), and a C-with-nesC extensions to C path (new). Accepts gcc options and nescc options, as filtered by nescc/nesc-compile.

Implementation is based on a C frontend derived from gcc 2.8.1, with various additions of code from later versions of gcc. Ideally it should support the current gcc C syntax, but that ends up being more an on-demand thing -- when someone complains that some header file doesn't work, I add support for whatever new C feature is involved. Essentially what's missing is some of the newer ISO C99 features, and all #pragma's. As of 1.3.x, the preprocessor is integrated in nesc1 (nesc1 used to invoke the target gcc to perform preprocessing of nesC files).

Directory Structure

• top-level: the usual configuration stuff, READMEs, etc. Bootstrap is a script that runs automake, autoconf, etc to generate configure

• doc: man pages, reference manual, and miscellaneous documentation

• include, libiberty, libcpp: integrated C preprocessor, imported from gcc in early 2008. Very minor (a few lines) changes (sorry, there should be a nice version number and diff, but it isn't very hard to track down exactly which snapshot I used, and hence recompute the diff).

• tests: old stuff, ignore.

• nregress: regression tests, execute ./runtest to run tests. Tests the nesc1 driver in src/nesc1, except some stuff depends on the installation too (this is broken and should be fixed, do a recursive grep for ncc and nescc)

• src: the nesC compiler itself (builds nesc1)

nesc1 structure

nesc-* contain the nesC-specific parts of the compiler. The other files are related to handling C, but have a limited amount of nesC-related changes.

The main files are:

• toplev.c: contains main, parses options and invokes nesc_compile
• nesc-main.c: nesc_compile is the main entry point to the actual compiler
• nodetypes.def, AST*.c: nodetypes.def defines the types representing the abstract syntax tree (AST) that is the parsed representation of a nesC program. The AST*.c files are hand-written and automatically-generated files for creating and manipulating AST nodes. See nesc-internals/AST for more details.
• c-lex.c: the lexer
• c-parse.y: the parser
• machine.c, machine.h, machine/*: cross-compilation support
• cval.c, constants.c: constants and constant folding
• expr.c: C expression handling
• init.c: C initializer handling
• semantics.c: C declaration handling (structures, variables, functions)
• stmt.c: C statement handling
• types.c: C type handling
• unparse.c: print a C program corresponding to an AST - contains various hacks for nesC support

• nesc-component.c: code common to configurations and modules
• nesc-configuration.c: configurations
• nesc-module.c: modules
• nesc-interface.c: interfaces
• nesc-abstract.c: generic components
• nesc-atomic.c: atomic statements
• nesc-attributes.c: nesC @blah(...) attributes
• nesc-magic.c: magic functions (unique & co)
• nesc-network.c: nx_* types
• nesc-task.c: tasks

• nesc-cg.c: cgraph is used to represent component connection graphs and function call/use graphs...
• nesc-constants.c: perform a constant-folding pass
• nesc-deputy.c: support for Deputy's type-safety annotations
• nesc-msg.c: mig support
• nesc-cpp.c: interaction between nesC and the C preprocessor
• nesc-xml.c, nesc-dump.c, nesc-dfilter.c, ND*, nesc-dspec.def: dump information on nesC program in XML (the .def and automatically-generated ND* files reuse the AST infrastructure
• nesc-doc.c: TinyOS 1.x documentation generator (obsolete, doesn't support generic components)
• nesc-ndoc.c: documentation string handling
• nesc-generate.c: nesC code generation (builds on unparse.c)
• nesc-inline.c: decide what to inline