source: README @ dbe7756

cfa-cc: The Cforall->C Compiler System
======================================

This is a PRE-RELEASE version of cfa-cc.  It exists solely for the purpose of
private experimentation and scholarly research.  The authors disclaim all
responsibility for the consequences of any malfunction of the software,
including the malfunction of any programs compiled using the software.

What is Cforall?
----------------
Cforall is a language design extending ISO C. The purpose of the project is to
engineer modern language features into C in an evolutionary rather than
revolutionary way. Java is an example of the revolutionary approach of
modernizing C/C++, resulting in a new language rather than an extension of its
descendents. C++, Fortran 95 and Cobol 9X are examples of the evolutionary
approach where modern language features are added and problems fixed within the
framework of an existing language.

The goal of this project is to produce a largely backwards compatible version
of C containing many modern language features and fixing some of the well known
C problems. Without continued development of the language, C will be unable to
cope with the needs of modern programming problems and programmers; as a
result, it will fade into disuse.  Considering the large body of existing C
code and programmers, there is a significant impetus to ensure C is transformed
into a modern programming language.

What is cfa-cc?
---------------
cfa-cc is a collection of programs centred around a translator that takes
Cforall code as input and outputs corresponding C code.  This is complemented
by a compiler driver in the style of "gcc", which handles preprocessing,
compiling, assembling, and linking and invokes the translator at appropriate
moments.

What is required in order to use cfa-cc?
----------------------------------------
Building cfa-cc requires GNU Make and gcc/g++ 4.  cfa-cc is written in C++.

The compiler driver uses an installed version of gcc to handle all aspects of
the compilation process except for the Cforall->C translation.  Currently, only
gcc 4.x is supported.

How is cfa-cc used?
-------------------
The compiler driver "cfa" accepts all of the arguments of gcc, and is used in
the same way.  For example:

        cfa -c test.c
        cfa test.o

Cforall source files must end with '.c' in order to be compiled by the compiler
driver.  In addition, the flag "-CFA" causes cfa to invoke the preprocessor and
translator and send the translator output to standard output.

It is possible to invoke the translator directly.  The translator is installed
by default as /usr/local/lib/cfa-cpp.  A typical invocation is:

        /usr/local/lib/cfa-cpp -cp infile outfile

If outfile is omitted, output goes to standard output; if infile is also
omitted, input comes from standard input.  Options to the translator other than
"-cp" will not produce valid C code and are only useful for debugging the
translator.

How can C code be used with cfa-cc?
-----------------------------------
cfa-cc should be able to compile most ANSI C programs.  It is also possible to
link against C libraries in most cases.  Since Cforall supports overloading,
however, names used in Cforall code are mangled in the output C code.  This
caused linker failures when the names refer to functions and objects in code
compiled with a standard C compiler.  For this reason, it is necessary to
enclose the declarations of these functions and objects in extern "C" {}
blocks.  For example:

        extern "C" {
        #include <stdio.h>
        #include <stdlib.h>
        }

The extern "C" turns off name mangling for functions and objects declared
within the block.  As a result, it is not possible to overload their names.

What's wrong with cfa-cc?
-------------------------

The authors consider this software to be in an unstable state.  It is quite
likely that there are many reasonable programs that will fail to compile.  We
encourage users to report their experiences to cforall@plg.uwaterloo.ca, but we
make no promises regarding support.

We have fixed most of the problems that we are aware of.  There are some
exceptions:

- initializers are poorly implemented; in particular, file-scope initializers
  may result in the generation of invalid C code

- the ISO C99 designated initialization syntax '[n] = m' or '.n = m' is not
  supported; use a colon in place of the equal sign

- some legitimate programs will produce warnings from the C compiler; these are
  harmless (in particular, the creation of libcfa.a in the build process should
  cause four warnings from gcc)

- abstract types introduced using the keyword 'type' are not implemented
  (although 'type' can be used to introduce type parameters)

- the implicit coercion of structure types to the type of their first member is
  not implemented
        
Who is responsible for cfa-cc?
------------------------------
cfa-cc was written by Peter Buhr, Richard Bilson, and Rodolfo Esteves.
Questions and comments can be sent to cforall@plg.uwaterloo.ca.

The Cforall project maintains a web page:

        http://plg.uwaterloo.ca/~cforall