O(3) Perl Programmers Reference Guide O(3)NAMEO - Generic interface to Perl Compiler backends
SYNOPSIS
perl -MO=Backend[,OPTIONS] foo.pl
DESCRIPTION
This is the module that is used as a frontend to the Perl
Compiler.
CONVENTIONS
Most compiler backends use the following conventions:
OPTIONS consists of a comma-separated list of words (no
white-space). The "-v" option usually puts the backend
into verbose mode. The "-ofile" option generates output
to file instead of stdout. The "-D" option followed by
various letters turns on various internal debugging flags.
See the documentation for the desired backend (named
"B::Backend" for the example above) to find out about that
backend.
IMPLEMENTATION
This section is only necessary for those who want to write
a compiler backend module that can be used via this mod
ule.
The command-line mentioned in the SYNOPSIS section corre
sponds to the Perl code
use O ("Backend", OPTIONS);
The "import" function which that calls loads in the appro
priate "B::Backend" module and calls the "compile" func
tion in that package, passing it OPTIONS. That function is
expected to return a sub reference which we'll call CALL
BACK. Next, the "compile-only" flag is switched on (equiv
alent to the command-line option "-c") and a CHECK block
is registered which calls CALLBACK. Thus the main Perl
program mentioned on the command-line is read in, parsed
and compiled into internal syntax tree form. Since the
"-c" flag is set, the program does not start running
(excepting BEGIN blocks of course) but the CALLBACK func
tion registered by the compiler backend is called.
In summary, a compiler backend module should be called
"B::Foo" for some foo and live in the appropriate direc
tory for that name. It should define a function called
"compile". When the user types
perl -MO=Foo,OPTIONS foo.pl
that function is called and is passed those OPTIONS (split
on commas). It should return a sub ref to the main compi
lation function. After the user's program is loaded and
parsed, that returned sub ref is invoked which can then go
ahead and do the compilation, usually by making use of the
"B" module's functionality.
AUTHOR
Malcolm Beattie, "mbeattie@sable.ox.ac.uk"
2001-03-18 perl v5.6.1 O(3)
