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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"

Index for Section 3

Alphabetical listing for B

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