B::CC

B::CC(3)               Perl Programmers Reference Guide               B::CC(3)



NAME
       B::CC - Perl compiler's optimized C translation backend

SYNOPSIS
               perl -MO=CC[,OPTIONS] foo.pl


DESCRIPTION
       This compiler backend takes Perl source and generates C source code
       corresponding to the flow of your program. In other words, this backend
       is somewhat a "real" compiler in the sense that many people think about
       compilers. Note however that, currently, it is a very poor compiler in
       that although it generates (mostly, or at least sometimes) correct
       code, it performs relatively few optimisations.  This will change as
       the compiler develops. The result is that running an executable
       compiled with this backend may start up more quickly than running the
       original Perl program (a feature shared by the C compiler backend--see
       B::C) and may also execute slightly faster. This is by no means a good
       optimising compiler--yet.

OPTIONS
       If there are any non-option arguments, they are taken to be names of
       objects to be saved (probably doesn't work properly yet).  Without
       extra arguments, it saves the main program.

       -ofilename
           Output to filename instead of STDOUT

       -v  Verbose compilation (currently gives a few compilation statistics).

       --  Force end of options

       -uPackname
           Force apparently unused subs from package Packname to be compiled.
           This allows programs to use eval "foo()" even when sub foo is never
           seen to be used at compile time. The down side is that any subs
           which really are never used also have code generated. This option
           is necessary, for example, if you have a signal handler foo which
           you initialise with $SIG{BAR} = "foo".  A better fix, though, is
           just to change it to $SIG{BAR} = \&foo. You can have multiple -u
           options. The compiler tries to figure out which packages may
           possibly have subs in which need compiling but the current version
           doesn't do it very well. In particular, it is confused by nested
           packages (i.e.  of the form A::B) where package A does not contain
           any subs.

       -mModulename
           Instead of generating source for a runnable executable, generate
           source for an XSUB module. The boot_Modulename function (which
           DynaLoader can look for) does the appropriate initialisation and
           runs the main part of the Perl source that is being compiled.

       -D  Debug options (concatenated or separate flags like perl -D).

       -Dr Writes debugging output to STDERR just as it's about to write to
           the program's runtime (otherwise writes debugging info as comments
           in its C output).

       -DO Outputs each OP as it's compiled

       -Ds Outputs the contents of the shadow stack at each OP

       -Dp Outputs the contents of the shadow pad of lexicals as it's loaded
           for each sub or the main program.

       -Dq Outputs the name of each fake PP function in the queue as it's
           about to process it.

       -Dl Output the filename and line number of each original line of Perl
           code as it's processed (pp_nextstate).

       -Dt Outputs timing information of compilation stages.

       -f  Force optimisations on or off one at a time.

       -ffreetmps-each-bblock
           Delays FREETMPS from the end of each statement to the end of the
           each basic block.

       -ffreetmps-each-loop
           Delays FREETMPS from the end of each statement to the end of the
           group of basic blocks forming a loop. At most one of the freetmps-
           each-* options can be used.

       -fomit-taint
           Omits generating code for handling perl's tainting mechanism.

       -On Optimisation level (n = 0, 1, 2, ...). -O means -O1.  Currently,
           -O1 sets -ffreetmps-each-bblock and -O2 sets -ffreetmps-each-loop.

EXAMPLES
               perl -MO=CC,-O2,-ofoo.c foo.pl
               perl cc_harness -o foo foo.c

       Note that cc_harness lives in the B subdirectory of your perl library
       directory. The utility called perlcc may also be used to help make use
       of this compiler.

               perl -MO=CC,-mFoo,-oFoo.c Foo.pm
               perl cc_harness -shared -c -o Foo.so Foo.c


BUGS
       Plenty. Current status: experimental.

DIFFERENCES
       These aren't really bugs but they are constructs which are heavily tied
       to perl's compile-and-go implementation and with which this compiler
       backend cannot cope.

       Loops

       Standard perl calculates the target of "next", "last", and "redo" at
       run-time. The compiler calculates the targets at compile-time.  For
       example, the program

           sub skip_on_odd { next NUMBER if $_[0] % 2 }
           NUMBER: for ($i = 0; $i < 5; $i++) {
               skip_on_odd($i);
               print $i;
           }

       produces the output

           024

       with standard perl but gives a compile-time error with the compiler.

       Context of ""..""

       The context (scalar or array) of the ".." operator determines whether
       it behaves as a range or a flip/flop. Standard perl delays until
       runtime the decision of which context it is in but the compiler needs
       to know the context at compile-time. For example,

           @a = (4,6,1,0,0,1);
           sub range { (shift @a)..(shift @a) }
           print range();
           while (@a) { print scalar(range()) }

       generates the output

           456123E0

       with standard Perl but gives a compile-time error with compiled Perl.

       Arithmetic

       Compiled Perl programs use native C arithemtic much more frequently
       than standard perl. Operations on large numbers or on boundary cases
       may produce different behaviour.

       Deprecated features

       Features of standard perl such as $[ which have been deprecated in
       standard perl since Perl5 was released have not been implemented in the
       compiler.

AUTHOR
       Malcolm Beattie, mbeattie@sable.ox.ac.uk



































3rd Berkeley Distribution    perl 5.005, patch 02                     B::CC(3)