source: README @ 8c17ab0

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++ 3.  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 3.2 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.

In cases where the compiler driver is not useful (i.e., where gcc 3.2
is not available), it is still 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 will cause 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.

It is our intention to have a transparent solution to this problem
in place for our first official release.

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