diff options
Diffstat (limited to 'pod')
| -rw-r--r-- | pod/perl.pod | 2 | ||||
| -rw-r--r-- | pod/perldelta.pod | 9 | ||||
| -rw-r--r-- | pod/perldiag.pod | 13 | ||||
| -rw-r--r-- | pod/perlguts.pod | 258 | ||||
| -rw-r--r-- | pod/perlport.pod | 4 | ||||
| -rw-r--r-- | pod/perltrap.pod | 3 |
6 files changed, 276 insertions, 13 deletions
diff --git a/pod/perl.pod b/pod/perl.pod index 87696fe55d..0275543c31 100644 --- a/pod/perl.pod +++ b/pod/perl.pod @@ -226,7 +226,7 @@ http://www.perl.com/CPAN/src/index.html 1) in DOS mode either the DOS or OS/2 ports can be used 2) formerly known as MVS 3) formerly known as Digital UNIX and before that DEC OSF/1 - 4) compilers: Borland, Cygwin32, Mingw32 EGCS/GCC, VC++ + 4) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++ The following platforms have been known to build Perl from source, but we haven't been able to verify their status for the current release, diff --git a/pod/perldelta.pod b/pod/perldelta.pod index 624b152075..ad0abccc6c 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -37,11 +37,15 @@ specified via MakeMaker: This new build option provides a set of macros for all API functions such that an implicit interpreter/thread context argument is passed to every API function. As a result of this, something like C<sv_setsv(foo,bar)> -amounts to a macro invocation that actually translates to +amounts to a macro invocation that actually translates to something like C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected to not have any significant source compatibility issues, the difference between a macro and a real function call will need to be considered. +This means that there B<is> a source compatibility issue as a result of +this if your extensions attempt to use pointers to any of the Perl API +functions. + Note that the above issue is not relevant to the default build of Perl, whose interfaces continue to match those of prior versions (but subject to the other options described here). @@ -50,6 +54,9 @@ For testing purposes, the 5.005_58 release automatically enables PERL_IMPLICIT_CONTEXT whenever Perl is built with -Dusethreads or -Dusemultiplicity. +See L<perlguts/"The Perl API"> for detailed information on the +ramifications of building Perl using this option. + =item C<PERL_POLLUTE_MALLOC> Enabling Perl's malloc in release 5.005 and earlier caused diff --git a/pod/perldiag.pod b/pod/perldiag.pod index bffd191174..47e16bfa5d 100644 --- a/pod/perldiag.pod +++ b/pod/perldiag.pod @@ -18,8 +18,11 @@ desperation): Optional warnings are enabled by using the B<-w> switch. Warnings may be captured by setting C<$SIG{__WARN__}> to a reference to a routine that will be called on each warning instead of printing it. See L<perlvar>. + Trappable errors may be trapped using the eval operator. See -L<perlfunc/eval>. +L<perlfunc/eval>. In almost all cases, warnings may be selectively +disabled or promoted to fatal errors using the C<warning> pragma. +See L<warning>. Some of these messages are generic. Spots that vary are denoted with a %s, just as in a printf format. Note that some messages start with a %s! @@ -1347,7 +1350,8 @@ the name. =item Format %s redefined -(W) You redefined a format. To suppress this warning, say +(W) You redefined a format, perhaps accidentally. To suppress this warning, +say { no warning; @@ -1979,8 +1983,6 @@ try using scientific notation (e.g. "1e6" instead of "1_000_000"). and therefore non-portable between systems. See L<perlport> for more on portability concerns. -See also L<perlport> for writing portable code. - =item Odd number of elements in hash assignment (S) You specified an odd number of elements to initialize a hash, which @@ -2614,7 +2616,8 @@ may break this. =item Subroutine %s redefined -(W) You redefined a subroutine. To suppress this warning, say +(W) You redefined a subroutine, perhaps accidentally. To suppress this +warning, say { no warning; diff --git a/pod/perlguts.pod b/pod/perlguts.pod index f297560b19..74b5ff99c4 100644 --- a/pod/perlguts.pod +++ b/pod/perlguts.pod @@ -1506,6 +1506,259 @@ additional complications for conditionals). These optimizations are done in the subroutine peep(). Optimizations performed at this stage are subject to the same restrictions as in the pass 2. +=head1 The Perl API + +WARNING: This information is subject to radical changes prior to +the Perl 5.6 release. Use with caution. + +=head2 Background and PERL_IMPLICIT_CONTEXT + +The Perl interpreter can be regarded as a closed box: it has an API +for feeding it code or otherwise making it do things, but it also has +functions for its own use. This smells a lot like an object, and +there are ways for you to build Perl so that you can have multiple +interpreters, with one interpreter represented either as a C++ object, +a C structure, or inside a thread. The thread, the C structure, or +the C++ object will contain all the context, the state of that +interpreter. + +Four macros control the way Perl is built: PERL_IMPLICIT_CONTEXT +(build for multiple interpreters?), MULTIPLICITY (we pass around an +C interpreter structure as the first argument), USE_THREADS (we pass +around a thread as the first argument), and PERL_OBJECT (we build a +C++ class for the interpreter so the Perl API implementation has a +C<this> object). If PERL_IMPLICIT_CONTEXT is not defined, then +subroutines take no first argument. + +This obviously requires a way for the Perl internal functions to be +C++ methods, subroutines taking some kind of structure as the first +argument, or subroutines taking nothing as the first argument. To +enable these three very different ways of building the interpreter, +the Perl source (as it does in so many other situations) makes heavy +use of macros and subroutine naming conventions. + +First problem: deciding which functions will be C++ public methods and +which will be private. Those functions whose names begin C<Perl_> are +public, and those whose names begin C<S_> are protected (think "S" for +"Secret"). You can't call them from C++, and should not call them +from C. If you find yourself calling an C<S_> function, consider your +code broken (even though it works, it may not do so forever). + +Some functions have no prefix (e.g., restore_rsfp in toke.c). These +are not parts of the object or pseudo-structure because you need to +pass pointers to them to other subroutines. + +Second problem: there must be a syntax so that the same subroutine +declarations and calls can pass a structure as their first argument, +or pass nothing. To solve this, the subroutines are named and +declared in a particular way. Here's a typical start of a static +function used within the Perl guts: + + STATIC void + S_incline(pTHX_ char *s) + +STATIC becomes "static" in C, and is #define'd to nothing in C++. + +A public function (i.e. part of the API) begins like this: + + void + Perl_sv_setsv(pTHX_ SV* dsv, SV* ssv) + +C<pTHX_> is one of a number of macros (in perl.h) that hide the +details of the interpreter's context. THX stands for "thread", "this", +or "thingy", as the case may be. (And no, George Lucas is not involved. :-) +The first character could be 'p' for a B<p>rototype, 'a' for B<a>rgument, +or 'd' for B<d>eclaration. + +When Perl is built without PERL_IMPLICIT_CONTEXT, there is no first +argument containing the interpreter's context. The trailing underscore +in the pTHX_ macro indicates that the macro expansion needs a comma +after the context argument because other arguments follow it. If +PERL_IMPLICIT_CONTEXT is not defined, pTHX_ will be ignored, and the +subroutine is not prototyped to take an argument. The form of the +macro without the trailing underscore is used when there are no +explicit arguments. + +When an core function calls another, it must pass the context. This +is normally hidden via macros. Consider C<sv_setsv>. It expands +something like this: + + ifdef PERL_IMPLICIT_CONTEXT + define sv_setsv(a,b) Perl_sv_setsv(aTHX_ a, b) + /* can't do this for vararg functions, see below */ + else + define sv_setsv Perl_sv_setsv + endif + +This works well, and means that XS authors can gleefully write: + + sv_setsv(foo, bar); + +and still have it work under all the modes Perl could have been +compiled with. + +Under PERL_OBJECT in the core, that will translate to either: + + CPerlObj::Perl_sv_setsv(foo,bar); # in CPerlObj functions, + # C++ takes care of 'this' + or + + pPerl->Perl_sv_setsv(foo,bar); # in truly static functions, + # see objXSUB.h + +Under PERL_OBJECT in extensions (aka PERL_CAPI), or under +MULTIPLICITY/USE_THREADS w/ PERL_IMPLICIT_CONTEXT in both core +and extensions, it will be: + + Perl_sv_setsv(aTHX_ foo, bar); # the canonical Perl "API" + # for all build flavors + +This doesn't work so cleanly for varargs functions, though, as macros +imply that the number of arguments is known in advance. Instead we +either need to spell them out fully, passing C<aTHX_> as the first +argument (the Perl core tends to do this with functions like +Perl_warner), or use a context-free version. + +The context-free version of Perl_warner is called +Perl_warner_nocontext, and does not take the extra argument. Instead +it does dTHX; to get the context from thread-local storage. We +C<#define warner Perl_warner_nocontext> so that extensions get source +compatibility at the expense of performance. (Passing an arg is +cheaper than grabbing it from thread-local storage.) + +You can ignore [pad]THX[xo] when browsing the Perl headers/sources. +Those are strictly for use within the core. Extensions and embedders +need only be aware of [pad]THX. + +=head2 How do I use all this in extensions? + +When Perl is built with PERL_IMPLICIT_CONTEXT, extensions that call +any functions in the Perl API will need to pass the initial context +argument somehow. The kicker is that you will need to write it in +such a way that the extension still compiles when Perl hasn't been +built with PERL_IMPLICIT_CONTEXT enabled. + +There are three ways to do this. First, the easy but inefficient way, +which is also the default, in order to maintain source compatibility +with extensions: whenever XSUB.h is #included, it redefines the aTHX +and aTHX_ macros to call a function that will return the context. +Thus, something like: + + sv_setsv(asv, bsv); + +in your extesion will translate to this: + + Perl_sv_setsv(GetPerlInterpreter(), asv, bsv); + +when PERL_IMPLICIT_CONTEXT is in effect, or to this otherwise: + + Perl_sv_setsv(asv, bsv); + +You have to do nothing new in your extension to get this; since +the Perl library provides GetPerlInterpreter(), it will all just +work. + +The second, more efficient way is to use the following template for +your Foo.xs: + + #define PERL_NO_GET_CONTEXT /* we want efficiency */ + #include "EXTERN.h" + #include "perl.h" + #include "XSUB.h" + + static my_private_function(int arg1, int arg2); + + static SV * + my_private_function(pTHX_ int arg1, int arg2) + { + dTHX; /* fetch context */ + ... call many Perl API functions ... + } + + [... etc ...] + + MODULE = Foo PACKAGE = Foo + + /* typical XSUB */ + + void + my_xsub(arg) + int arg + CODE: + my_private_function(arg, 10); + +Note that the only two changes from the normal way of writing an +extension is the addition of a C<#define PERL_NO_GET_CONTEXT> before +including the Perl headers, followed by a C<dTHX;> declaration at +the start of every function that will call the Perl API. (You'll +know which functions need this, because the C compiler will complain +that there's an undeclared identifier in those functions.) No changes +are needed for the XSUBs themselves, because the XS() macro is +correctly defined to pass in the implicit context if needed. + +The third, even more efficient way is to ape how it is done within +the Perl guts: + + + #define PERL_NO_GET_CONTEXT /* we want efficiency */ + #include "EXTERN.h" + #include "perl.h" + #include "XSUB.h" + + /* pTHX_ only needed for functions that call Perl API */ + static my_private_function(pTHX_ int arg1, int arg2); + + static SV * + my_private_function(pTHX_ int arg1, int arg2) + { + /* dTHX; not needed here, because THX is an argument */ + ... call Perl API functions ... + } + + [... etc ...] + + MODULE = Foo PACKAGE = Foo + + /* typical XSUB */ + + void + my_xsub(arg) + int arg + CODE: + my_private_function(aTHX_ arg, 10); + +This implementation never has to fetch the context using a function +call, since it is always passed as an extra argument. Depending on +your needs for simplicity or efficiency, you may mix the previous +two approaches freely. + +Never say C<pTHX,> yourself--always use the form of the macro with the +underscore for functions that take explicit arguments, or the form +without the argument for functions with no explicit arguments. + +=head2 Future Plans and PERL_IMPLICIT_SYS + +Just as PERL_IMPLICIT_CONTEXT provides a way to bundle up everything +that the interpreter knows about itself and pass it around, so too are +there plans to allow the interpreter to bundle up everything it knows +about the environment it's running on. This is enabled with the +PERL_IMPLICIT_SYS macro. Currently it only works with PERL_OBJECT, +but is mostly there for MULTIPLICITY and USE_THREADS (see inside +iperlsys.h). + +This allows the ability to provide an extra pointer (called the "host" +environment) for all the system calls. This makes it possible for +all the system stuff to maintain their own state, broken down into +seven C structures. These are thin wrappers around the usual system +calls (see win32/perllib.c) for the default perl executable, but for a +more ambitious host (like the one that would do fork() emulation) all +the extra work needed to pretend that different interpreters are +actually different "processes", would be done here. + +The Perl engine/interpreter and the host are orthogonal entities. +There could be one or more interpreters in a process, and one or +more "hosts", with free association between them. + =head1 API LISTING This is a listing of functions, macros, flags, and variables that may be @@ -1514,10 +1767,7 @@ extensions. Note that all Perl API global variables must be referenced with the C<PL_> prefix. Some macros are provided for compatibility with the older, -unadorned names, but this support will be removed in a future release. - -It is strongly recommended that all Perl API functions that don't begin -with C<perl> be referenced with an explicit C<Perl_> prefix. +unadorned names, but this support may be disabled in a future release. The sort order of the listing is case insensitive, with any occurrences of '_' ignored for the purpose of sorting. diff --git a/pod/perlport.pod b/pod/perlport.pod index 5c0c71cd72..6b532f3777 100644 --- a/pod/perlport.pod +++ b/pod/perlport.pod @@ -663,8 +663,8 @@ C<ftp://hobbes.nmsu.edu/pub/os2/dev/emx> =item The ActiveState Pages, C<http://www.activestate.com/> -=item The Cygwin32 environment for Win32; L<README.cygwin32>, -C<http://www.cygnus.com/misc/gnu-win32/> +=item The Cygwin environment for Win32; L<README.cygwin>, +C<http://sourceware.cygnus.com/cygwin/> =item The U/WIN environment for Win32, C<http://www.research.att.com/sw/tools/uwin/> diff --git a/pod/perltrap.pod b/pod/perltrap.pod index 321c86dd7f..50987cb102 100644 --- a/pod/perltrap.pod +++ b/pod/perltrap.pod @@ -761,6 +761,9 @@ Hashes get defined before use # perl4 prints: # perl5 dies: hash %h defined +Perl will now generate a warning when it sees defined(@a) and +defined(%h). + =item * (Globs) glob assignment from variable to variable will fail if the assigned |