B::CC - Perl compiler's optimized C translation backend
perl -MO=CC[,OPTIONS] foo.pl
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.
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.
$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.
perl -D).
pp_nextstate).
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
Plenty. Current status: experimental.
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.
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.
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.
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.
Features of standard perl such as $[ which have been deprecated in standard perl since Perl5 was released have
not been implemented in the compiler.
Malcolm Beattie, mbeattie@sable.ox.ac.uk
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.