=head1 NAME tools/build/pmc2c.pl - PMC definition to C compiler =head2 Internals To see the internal data structures please run: % perl tools/build/pmc2c.pl --c --debug --debug sarray.pmc | less =head2 Compiling PMCs First, the program determines the names of the .c and .h files from the basename of the .pmc file (e.g. F<perlint.pmc> -> F<perlint.c> and F<perlint.h>). Next, the file is searched for C</pmclass \w*/> which attempts to find the class being declared. Once the class is found, all of its superclasses are scanned and their methods added to the methods of the current PMC. PMCs default to inheriting from 'default'. Only single inheritance is supported. Once the superclass is determined, it is processed and its method names are extracted and saved. Next, each method body is processed with various directives (see below) getting replaced by their appropriate values. Finally, the .c and .h files are generated. The appropriate base class header files are included. If the C<no_init> flag was used, then no init function is generated. Otherwise, one is generated which sets up the vtable and enters it into the C<vtables> array. The .c file is generated by appending the functions after the various directives have been replaced. =head2 PMC File Syntax The basic syntax of a PMC file is =over 4 =item 1. A preamble, consisting of code to be copied directly to the .c file =item 2. The C<pmclass> declaration: pmclass PMCNAME [flags] { where C<flags> are: =over 4 =item C<extends PMCPARENT> All methods not defined in PMCNAME are inherited from the PMCPARENT class. If no parent class is defined, methods from F<default.pmc> are used. =item C<abstract> This class cannot be instantiated. Abstract classes are shown with lower case class names in the class tree. =item C<no_init> Used with C<abstract>: No C<class_init> code is generated. =item C<const_too> Classes with this flag get 2 vtables and 2 enums, one pair with read/write set methods, and one with read-only set methods. =item C<does interface> The class 'does' the given interfaces (the collection of methods which the class implements). The default is "scalar". Other currently used interfaces are: array : container PMC with numerically-keyed elements event : PMC that can be used with event queue hash : container PMC with string-keyed elements library : PMC that corresponds to a dynamic library ref : PMC that references another PMC string : PMC that behaves similarly to the base string type boolean : PMC that does true/false only. integer : PMC that behaves similarly to the base int type float : PMC that behaves similarly to the base number type scalar : (only used by the sample src/dynpmc/foo.pmc) This is not a canonical list, but merely a snapshot of what's in use. =item C<dynpmc> The class is a dynamic class. These have a special C<class_init> routine suitable for dynamic loading at runtime. See the F<src/dynpmc> directory for an example. =item C<group GROUP> The class is part of a group of interrelated PMCs that should be compiled together into a single shared library of the given name. Only valid for dynamic PMCs. =item C<lib LIB> The class needs an external library. =item C<hll HLL> The High level language this PMC corresponds to. =item C<maps Type> The basic parrot PMC type that this PMC correspond to for C<.HLL> usage. For example: pmclass TclInt hll Tcl maps Integer allows this PMC to automatically be used when autoboxing C<I> registers to PMCs. Requires the C<hll> flag. Note that multiple mappings can be specified: pmclass myOrderedHash hll frob maps Hash maps Array =back =item 3. A list of vtable method implementations =item 4. The final close C<}> =back =head2 Method Body Substitutions The vtable method bodies can use the following substitutions: =over 4 =item C<SELF> Converted to the current PMC object of type C<PMC *>. =item C<INTERP> Converted to the interpreter object. =item C<OtherClass.SELF.method(a,b,c)> Calls the static vtable method 'method' in C<OtherClass>. =item C<SELF.method(a,b,c)> Calls the vtable method 'method' using the dynamic type of C<SELF>. =item C<SELF(a,b,c)> Same as above, but calls the current method. =item C<STATICSELF.method(a,b,c)> Calls the vtable method 'method' using the static type of C<SELF> (in other words, calls another method defined in the same file). =item C<OtherClass.SUPER(a,b,c)> Calls the overridden implementation of the current method in C<OtherClass>. =item C<SUPER(a,b,c)> Calls the overridden implementation of the current method in the nearest superclass, using the type of C<SELF>. =back =head1 AUTHOR Leopold Toetsch. Cleaned up by Matt Diephouse. Many thanks to the author of F<pmc2c.pl>, many useful code pieces got reused. =cut