Extending and Embedding Perl 145
| Extending and Embedding Perl | |
| author | Tim Jenness and Simon Cozens |
| pages | 375 |
| publisher | Manning (http://www.manning.com/) |
| rating | 8.7 out of 10 |
| reviewer | habit forming |
| ISBN | 1930110820 |
| summary | Get in touch with the inner Perl. |
What's that up your sleeve?
It is my experience that many situations require us to "look under the hood" of (thoroughly examine) a solution to understand how to best use it effectively. Perl is no exception. The ability to bring such a force as Perl to a project at the proper time is a valuable skill to possess. However, wading chest-deep into XS and the Perl internals is not for the faint of heart. Jenness and Cozens ease this process by stepping in lightly at first.
What's in it?
The book begins with simple C examples that are then related back to the readers' knowledge of Perl. Then the text seems to throw us a curve by leaping off into building Perl modules. But there is method to the madness: building Perl modules correctly is inextricably linked to XS. Light introductions to XS are performed and the reader is well on his/her way to building .so extensions to any .pm.
After building a very specific foundation of simple C examples, module building, and some XS, the text returns to C to introduce pointers, arrays, file I/O and memory management. With these new skills, we begin to explore the structure and implementation of Perl variable types. Chapter 4 provides many useful diagrams of how Perl variables "look" and what C structures they translate into.
Still following a logical and constant order, we explore the Perl 5 API, learning how to post and retrieve information to the variable types explored in the previous chapter. As much as it might seem, this is not a rehash of the perlapi doc. It is consistent with the perlapi doc, but Jenness and Cozens provide extensively annotated C code examples.
Casting deeper still, we add the advanced C of pointers, arrays, file I/O and memory management to our knowledge of XS. At this point we have everything we need to effectively extend Perl, but the text continues deeper still by exploring how XSUB interfaces to Perl's internals. It is only the clearly documented, step-by-step explanations of this chapter that make it manageable for an average user like myself. Chapter 7 ends our stint with XS by discussing some alternative XS (or equivalent code) generation suites.
Switching gears entirely, we grab libperl.a and stuff into a C program. Chapter 8 begins the task of embedding Perl into a C program. Jenness and Cozens continue the embedded discussion through a Case Study in Chapter 9 and end with a look through the Perl internals in Chapter 10.
The final chapter (Chapter 11) details some of Perl's history, its development process, how we could become involved and what the future of Perl and Perl 6 may entail.
Final Thought
This book was indispensable in gaining a good foothold on using Perl in, from, and around C. I found it a good reference guide as well as an easy ,linear read. It is not a replacement for the perlguts, perlapi and perlxs documentation, but then again, it doesn't try to be. The annotated code examples with every line explained make following the book with development of your own solution a lot easier than in some other books. However, the in-depth explanations can be a bit frustrating for the impatient.
You can purchase Extending and Embedding Perl from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
XS Isn't the only way. (Score:5, Informative)
Re:XS Isn't the only way. (Score:3, Informative)
Python makes it much easier to interact with C libraries, and Ruby has the nicest C library support of all. Also, for embedding a program language into an application, why not use Scheme? It was designed to be embedded from the beginning and should impose much less overhead. Since it's a functional language, it's also very well suited for AI, which makes it a good choice for games and such.
I'm not knocking Perl. It has a special place in my heart as the first language I really learned; however, it's best used for what it's really good at, and that's scripting.
Re:XS Isn't the only way. (Score:2)
Damn, I agree. I could have written exactly the same thing. Except for Ruby which I don't really know about, but Scheme is just the best thing to enhance a C program and give it the dynamism it lacks.
Re:The author talks about alternatives (Score:2, Informative)
Perl and C relationship summed in 1 word: (Score:2, Funny)
Combining C and Perl (Score:5, Funny)
Re:Combining C and Perl (Score:4, Insightful)
Far too much has been made of Perl readability. Yawn. Recently I opened up some code I wrote four years ago for a rather obscure application that I hadn't looked at since. After a minute, and only about a minute, I understood it perfectly. Granted, I wrote it, but similarly I rarely have problems reading other programmers' Perl code, if it's well written or at least well written enough.
Poorly written code is hard to read in any language, but Perl isn't very difficult. Sure, there's the odd regular expression that's difficult to decipher, but overall it's how well you know the language in question.
It just frequently seems that the readability issue seems to be centered around how well the code can be read by readers not only new to the code but new to the language as well.
For that matter, far too much has been made of Python's readability. I'll grant that Python isn't difficult to read, but I've seen some pretty goofy Python code, as well as Perl. Python, or any language for that matter, can be nicely obfuscated just by naming variables poorly.
And as far as memory protection in C is concerned, well, it's no worse than assembly, and C is smokin' fast when written properly.
In short, you want to go fast, then you're going to be driving Indycar and it's going to be risky for the amateurs. You want safe? Try Java, and buy a Prius.
Perl 5 API??? (Score:3, Insightful)
Isn't Perl 6 coming out soon?
Maybe the author should have held off releasing this book
Re:Perl 5 API??? (Score:3, Interesting)
Re:Perl 5 API??? (Score:5, Informative)
Isn't Perl 6 coming out soon?
"Soon"? Considering that they haven't even finished [perl.org] deciding the features and changes of Perl 6, I think it's safe to say that a release version is at least a few years off, with 50% adoption being another three years plus after that.
Re:Perl 5 API??? (Score:2, Informative)
True, Perl 6 is coming, but the shape of the language is still being discussed, the virtual machine isn't doing that much yet, and there's not really anything substantial yet... it may take a year or two until Perl 6 is out (not sure about the developers' actual schedule, though).
As far as I know, there's not many (if any?) books that discuss the XS or Perl embedding. It sure isn't covered that widely in the Camel or Ram, and the only reference has been "go RTF 'perldoc perlxs'"... =)
And most importantly, the Perl 6 folks have not said a word about how XS and embedding stuff works in Perl 6. (I suspect that it will be radically different, because of the Parrot...)
Re:Perl 5 API??? (Score:3, Informative)
They have said a lot about it: XS is going away completely, and interfacing C to Perl is going to get a lot easier. (The quote I remember from their FAQ was something like "how could it be any harder than it already is?")
As far as embedding Perl, well, the Perl interpreter is going to be written in Perl starting with Perl 6. Instead of embedding an interpreter, I think you'd just embed a Parrot VM and hook your compiled Parrot bytecode into your program.
Re:Perl 5 API??? (Score:1)
Yeah, I figured it would be something like this =) XS is pretty arcane.
Thanks for this interesting nugget of information...
Re:Perl 5 API??? (Score:3, Informative)
Maybe the author will make more $$$ releasing the perl 5 book now, and the 'revised' perl 6 version next year
Also don't forget the sometimes extremely long lead times for book publishing, it is entirely possible that the author finished this book 6+ months ago.
And last but not least, yeah, perl 6 is going to come out soon, but do you really think I'm going to use it for production code right away? I really don't think so, perl 5 will be the tool of choice for quite a while longer.
Re:Perl 5 API??? (Score:5, Informative)
You'll still be able to run your Perl 5.x scripts under 6, but not vice-versa. Thus, with all the existing Perl 5.x scripts existing in the wild, having a Perl 5 book around may still be handy.
If you like analogies: why would you buy a C book when C++ has been around for years?
-- Hamster
Bad analogy (Score:1)
Re:Perl 5 API??? DEAD END! (Score:1)
Re:Perl 5 API??? (Score:2, Insightful)
We all hope so, but it's not necessarily going to be released even in the next year or two. In the meantime, Perl 5 is more widely used than ever. And even after Perl 6 does come out, it will take a long time for people to switch over, assuming they do decide to switch. Heck, there's still a lot of Perl 4 code out there even though Perl 5 has been out for... like 8 years?
Re:Perl 5 API??? (Score:2)
Only for certain values of "soon". My recollection is that estimates were that it would begin to be available in some useable form after 2 years (this was probably a year ago). I think it will be much longer before it's production ready, though that's just a guess, and several more before perl5 goes away.
Re:Perl 5 API??? (Score:3, Interesting)
I do have a half dozen Perl books and I barely survived my first foray into XS. Maybe this book can help me go back and get it right.
Re:Perl 5 API??? (Score:3, Funny)
But are you a good programmer? ;-)
Re:Perl 5 API??? (Score:2)
Touche' :-)
Give that one a funny, moderators.
Perl 4 is still in production (Score:1)
The guy that runs our UNIX services says that they're slowly phasing it out, and expect to be done by mid 2004.
Nobody has touched this old code till' present because, well, they were afraid of screwin up the prod environment.
My point? Perl 5 is much more widespread than 4. Given that, and Larry's statments that 5 code will run on the 6 interpreter, I think that it's safe to buy Perl5 books. The dialect isn't going to die anytime soon methinks.
interpreter for other applications (Score:5, Interesting)
Re:interpreter for other applications (Score:5, Informative)
Our ASCII file import parsers are written in Perl and the data read into Perl data-structures. The contents of these data structures can then be accessed directly from C++.
The code is on the web (it has some subtle C++ bugs needed fixes using the base-from-member inititialisation idiom) here [willnolan.com]
Ruby anyone? (Score:1)
Right now my choice is set on Ruby. I plan of using it with my C++ engine replacing traditional ObjectViews by Ruby Objects. I've just got started on this task but already I have good hope on Ruby. dRuby (Distributed Ruby) has a 200lines networked distributed objects system that really kick ass!
Someone told me I might want to look into Boost::python binding. I also thought of Perl to do this, having done a little bit of perl scripting (mostly with MySQL). Anyone have comments on embedding Ruby with C++ ?
Re:interpreter for other applications (Score:1, Interesting)
Re:interpreter for other applications (Score:1)
shootout [bagley.org]
even though it certainly isn't the fastest. One of the nice things about Tcl is that it's much easier to write C code to use from Tcl, or vice versa, which makes it very easy to speed up slow portions of your code with C.
With a good, clean interface, it's a lot of fun to write two-tiered applications, in addition to being an extremely powerful way of doing things. Look at any large enough app, and you are bound to find a scripting language of some kind, be it VB, Tcl, Lisp, Lua, elastiC, or something else...
Re:interpreter for other applications (Score:1)
Save yourself 6 months of programming, use perl and buy a slightly faster CPU.
Re:interpreter for other applications (Score:2)
There is also the compilation step. You've felt the overhead when compiling new code, no doubt. This would need to be done during some other load time in the game.
Perl is Perl, C is C (Score:4, Interesting)
It's much like the great masters of Funk, The Parliament once said: "I've been down to the south, saw some great Funk...The Doobie Brothers...but do you want white guys all up in your Funk?"
In the same way, "I've been down through the source, I saw some great code...Perl...but do you want scripts all up in your C?"
Re:Perl is Perl, C is C (Score:5, Insightful)
I've done this on serveral occasions... did you ever have a huge project to finish in a small amount of time that had some sort of processor-critical portion that's run alot? Well then, I would suggest writing it in Perl and then optimizing that piece in C. Works for me.
Often in the "real world" you can't have your cake and eat it, too. That's why people embed C in Perl.
Re:Perl is Perl, C is C (Score:5, Insightful)
But many projects need both low-level access to X/graphics/system libraries and really do benefit from the high-level approach of Perl.
In many cases, there are already libraries available that link the two together (e.g. Perl/Tk if you're writing in Perl, or associative array libraries for use from C) but it's never been a secret that you can call C code from Perl. You seem to advocate keeping it a secret.
Re:Perl is Perl, C is C (Score:1)
umm... hello? (Score:4, Informative)
As for C in Perl... Perl is a scripting language, it's simply not fast enough for everything, and you're going to need C to access different things, like joysticks, video, graphics libraries, etc...
wtf you talkin bout' foo? (Score:1)
Nice troll though...
Re:Perl is Perl, C is C (Score:2, Insightful)
It's all about the right tool for the right part of the job.
Re:Perl is Perl, C is C (Score:3, Funny)
PERL [cpan.org] doesn't have any extensions! It's only a guestbook and hit counter programming language.
Re:Perl is Perl, C is C (Score:1)
From that link, anyone else find this sentence disturbingly true?:
It is a direct descendent of Perl, a programming language which was used mainly by programmers. However, the original language required too much reading and thinking and so PERL was developed as a language which was more in tune with the requirements of the Internet age.
Re:Perl is Perl, C is C (Score:2)
I can't think of any real reason to actually do so
I agree. Scripting seems best for a quick and dirty approach, while actually writing some C or C++ takes more time and consideration. I can't see why you want to mix the two, unless of course you need some low level access to hardware that Perl doesn't offer directly...
Re:Perl is Perl, C is C (Score:4, Interesting)
Spoken like a dumb college student. I work for a small company started by my friend from college. We do everything almost exclusivly in perl (with some PHP). Our application is mostly a CGI interface to a obscenely diesel MySQL server (80 GB+, some tables have over 300 million rows, you dirty mysql nay-sayers). It has some low level functions that I wrote in C. It's extrememly modular. Perl has allowed us to write small daemon programs quickly. As our system grows large and larger, we're easily able to replace to slow performing sections with a optimized C version of the same daemon.
We took our particular space (I'd rather not get into it) by storm. Me and one other developer worked day and night for 6 months and we now have a product that we license for between $50,000 and $250,000 depending on how the client wants to scale. It is easily in the top 3 of similar programs. And it was written by me and another dude. In Perl. With some C. In 6 months.
As much as I love C and have mixed emotions about perl, if it was written in C we'd still be core dumping and our company would have probably gone out of business, as opposed to quadrupling in size and increasing our gross income 10 fold. Again, I hate perl, even, but there's no replacement for it. I, like you, was once a dumb college student who swore I would never write anything but C. But, then I graduated and realized I needed 22" dubs on my escalade. (okay, I have neither 22" dubs, or an escalade, but you can imagine if I did, right?).
C and C++ do take more time and consideration, and when you're part of a lean and mean company you do what you need to get ahead. If it wasn't for perl I'm 100% sure that we would not be where we are today.
Re:Perl is Perl, C is C (Score:1)
In summary, you are saying that you made a quick (but not entirely dirty) solution in Perl to gain market postion, but it won't scale. To make it scale you need a more considered solution written in C (or any other lower level language), which you intend to implement in pieces - starting at the bottle necks.
So actually, you probably don't want to mix C and Perl at all (you even say that you hate Perl), but were forced to by market pressure and probably a lack of capital (and skill from the sound of it) to make the whole system in C in the first place. I think you are agreeing with me here afterall - thanks.
Oh, and I'm not a college student, or dumb; what is dumb is your attitude.
Re:Perl is Perl, C is C (Score:2)
What you are effectively advocating is the waterfall model, a software methodology that hardly anyone considers a good idea anymore (it's only kept alive by stupid companies, I've yet to find a developer who prefer it).
If you have no idea what I'm talking about, the waterfall model is the old method of producing software: analyze, design, write, test, deliver. You will have no idea of whether your product actually works before you are in the test phase, and then it's too late to back out, so your company will have to spend a lot to pay for the delayed product (because problems will occur). By the time you actually deliver the product, the requirements will have changed, and it can no longer be used.
Modern software development methodologies advocate an iterative approach. You analyse, design and write a small part of the whole system, preferably the part that's most critical (thus you find out early if the product is feasible), test it, revise your plan, and then do the next part. This way, you will always have a working tested system, and you can focus on stability long before you have all the features in place. And, just as important, when requirements change, you can change the direction you are going in, without scrapping everything you've done so far.
Another epitome of good software engineering practice was best said by Edsger Dijkstra: "Premature optimization is the root of all evil". While C will give you better performance if you have the time for it, and assembler even better, it's much better to first write something that works, and then optimize the bottlenecks. This way, you will only have unmaintainable code in the few critical parts that needs it (90% of the time is spent in 10% of the code).
You should also read Richard P. Gabriels classic paper "Worse is Better [naggum.no] for a better explanation of why this approach is sensible. After having done that, you can then consider rereading the part that says "if it was written in C we'd still be core dumping and our company would have probably gone out of business", and see if it makes more sense to you now.
PS: I've just made some dumb waterfall-like mistakes myself, so I know what I'm speaking of :-)
Re:Perl is Perl, C is C (Score:1)
Creating a prototype is part of the Iterative model, not the Waterfall model. If you insist that it is Waterfall, then you are accepting that you are performing two rounds of Waterfall, one for prototype and one for release, which is really just two cycles of iterative. Of course a proper application of the Iterative development model would have more than 2 cycles and they would each be about as long as the prototype cycle.
Confused? I figured you would be.
Re:Perl is Perl, C is C (Score:3, Interesting)
Re:Perl is Perl, C is C (Score:1)
Dude, I don't know what you're talking about, but that sounds really rude to me.
Re:Perl is Perl, C is C (Score:1)
XS Mechanics (Score:5, Informative)
XS Mechanics
Followup book coming soon... (Score:5, Funny)
My $0.02 (Score:4, Informative)
It's amazing how much this book covers: Not only does Sam Tregar show how object-oriented Perl modules are architected, how to write regression test suites, how to extend Perl modules with C code, but he gets also the community aspects right -- how does your module get really popular? You can tell that Sam is a successful Perl module author himself.
-dk
Re:My $0.02 (Score:4, Informative)
You seem to be thinking of Writing Perl Modules for CPAN [slashdot.org]. There are similarities, but the Jenness/Cozens book goes into more detail about XS than the Tregar book. That's to be expected.
Re:My $0.02 (Score:1)
-dk
Re:My $0.02 (Score:1)
I've read both books. They have a great deal in common. I did not consult Sam's book directly before responding, though, so I'm going from memory as to how much detail he provided in the two or three XS chapters.
Obviously not a very good book (Score:3, Funny)
Re:Obviously not a very good book (Score:1)
I think Perl5/XS will be with us for long time... (Score:4, Informative)
Recently, the DotGNU have made an overture [develooper.com] to try to use the Parrot runtime for their C# compiler but found that Parrot needs a lot of work to get to the point where they could use it.
Some Parrot VM problems:
no calling conventions yet for subroutines. There is no hope of offering mixed language support unless they do this.
no conversion opcodes for various builtin types (float, char, short, int)
non-perl languages expected to provide additional support in the form of C code libraries for their opcodes. This would nix any hope of having a single standard universal virtual machine.
no way to call out to C code
no equivalent of Java's jar file or CLR's assemblies for parrot library distribution
way too many registers: their register based VM (32 int registers, 32 double registers, 32 string registers, 32 PMC registers plus various stacks) requires a sophisticated compiler to do proper register allocation and needlessly complicates their VM.
no consideration of threads in their design. How will they handle synchronization, for example?
The points above are not coding issues, but issues of design. It seems that Parrot is too hung up on making the VM efficient and are not seeing the bigger picture - to get the features in place first so that high-level languages can work. Or perhaps they should simply concentrate on getting Perl6 to work first. They need more focus. The project tries to be all things to all people, but ends up satisfiying no one.
Re:I think Perl5/XS will be with us for long time. (Score:5, Informative)
- no calling conventions yet for subroutines. Alas not true. They're in place and have been for quite some time.
- no conversion opcodes for various builtin types Also incorrect--we've got them and have since the very beginning. What we don't have is low-level support for specific size integer and floats, since our target languages (perl, python, ruby) don't have them. Adding them adds no overhead, though, so they're going in since it'll make base
.NET and JVM compatibility simpler.
- non-perl languages expected to provide additional support in the form of C code libraries for their opcodes. Once again, incorrect. No external libraries are or will be required. We're turing complete and generally have a richer set of base semantics than
.NET or the JVM does. This doesn't mean that someone can't choose to require an alternate set of opcodes if they want, but the engine doesn't require it.
- no way to call out to C code This one's actually true. We've not gotten to that part yet, though it's on the list.
- no equivalent of Java's jar file or CLR's assemblies for parrot library distribution Incorrect, bytecode files work just fine for this. That part of the design is somewhat incomplete, though.
- way too many registers: their register based VM
... requires a sophisticated compiler to do proper register allocation and needlessly complicates their VM Wrong yet again, sorry. Doesn't requore a sophisticated compiler at all. At best it requires some sophisticated register allocation algorithms. Luckily for us, those algorithms are old, known territory, which is why we've got them implemented already. So what if it makes the VM slightly more complex? (And it is only slightly more complex because of it) We're not writing something for CS101 here.
- no consideration of threads in their design. Once again, incorrect, if you'd bothered to read any of the design documents. Threading isn't, at the moment, implemented because other things have been more important, but it has been thought about in the design.
1.5 for 7. Not too good there. Oh, and this: What drugs are you on? If we piss away efficiency in the design, no amount of clever coding will ever get it back. Maybe you're willing to sacrifice a factor of two in speed for "clarity" but so are nine of your friends. (To misquote the author of make) I, on the other hand, am not.Finally
If you'll look, you'll notice that perl 6 isn't fully designed yet, but the bits that are have been implemented.Just because you can't (or won't, or don't want to) see the focus doesn't mean it's not there. It is, thanks very much, and we're well on track to do what we need and do it well. The design's flexible enough to pick up things like JVM or .NET compatibility without a loss of focus or efficiency, so there's no reason not to.
Re:I think Perl5/XS will be with us for long time. (Score:2, Interesting)
The Parrot calling convention POD was pulled a while back. I don't call saveall/restoreall a true calling convention. Prove me wrong - show me a doc with the new calling convention.
Where's Parrot's 64 bit integer type? If you hope to support Java and C# you will need it.
You *do* need some form of distributable bytecode library format - bytecodes alone do not cut it - all projects cannot be monolithicly compiled in a single bytecode file.
Threading issues *must* be considered from the very start - it affects every aspect of your design - from garbage collection to memory layout. Look at all the trouble Perl 5 had grafting threads to its design - they only "got it right" in Perl 5.8.
You're living in a dream world of denial. The project has to address these basic issues if it is to suceed.
It's history repeating itself all over again. Remember what happened to Topaz: Perl for the 22nd Century [perl.com]?
Re:I think Perl5/XS will be with us for long time. (Score:5, Interesting)
The only part of history repeating itself is the naysaying from people who've not done their research. If you're going to criticize, at least get it right.
Re:I think Perl5/XS will be with us for long time. (Score:1)
Re:I think Perl5/XS will be with us for long time. (Score:5, Informative)
There's nothing particularly wrong with saying "You must have the X library/module/kit to do Y". Requiring the install of the
What's next, will you start complaining next that we're going to require installing Postgres to access Postgres databases? (Or will the next complaint be about the bloated size of the distribution to provide the features that match your expectations?)
Re:I think Perl5/XS will be with us for long time. (Score:1)
By delaying the decision on how to hook up Parrot to native C APIs you are denying Parrot critical third party support. Like guys who simply want to embed Parrot in their application to control a MP3 player or CAD program or whatever. You need the buy in, you need the additional free testers and proponents. Give them a reason to use Parrot at this stage.
Actually this talk of C#/dotGNU/Parrot integration is a good thing - it will give Parrot some focus to run a real language. Perl6 is not the greatest target at this because it keeps shifting.
Re:I think Perl5/XS will be with us for long time. (Score:1, Informative)
PPC G4 lacks key builtin opcodes for universal language support - like support for 64 bit ints.
Java VM lacks key builtin opcodes for universal language support - like support for 64 bit ints.
You do understand that Parrot is a VM, don't you?
Re:I think Perl5/XS will be with us for long time. (Score:2)
If I remember the talks Dan has given to Boston.pm correctly, you've got this almost completely backwards. A more accurate reading is that Parrot is designed to act as kind of a superset of the target languages (Perl, Python, and Ruby) and that, in the handful of cases where an abstracted general feature of Parrot doesn't map perfectly back to the languages, any of those languages -- *including Perl* -- may have to adapt to Parrot's needs. In other words, Parrot has certain features because the Python & Ruby folks needed them, and these will require Perl to adapt if it wants to take advantage. (If we're lucky, Dan may clarify &/or add to this -- it's been a few months now and I forget most of the details of the presentation...).
So let's not have this kind of trolling, please. If you think Parrot is making such fundamental mistakes, help out or fork off your own project to prove yourself. Antagonistically spouting off half-correct technical gibberish on Slashdot isn't helping anyone.
Save some money (Score:3, Informative)
----
Associates Link
Re:Save some money (Score:5, Informative)
http://www.manning.com/jenness/index.html
Save even more money (Score:2)
pcre (Score:4, Informative)
Interfacing Perl with C... (Score:5, Informative)
In my case, I'm part of a large scale C++ project. I have the ownership of a module with clearly defined interfaces with the other modules written in this project.
Since my module relies heavily on XML and strings, I have always wanted to pair it with the power of Perl for testing purpose.
Among various possibles solutions (XS, SWIG, etc.), I settled on SWIG because it could handle 'shallow' classes. (allowing to expose my module as a perl object)
This has been the best decision I have made over the last year: when I get a bug case, I simply write a perl script to try to reproduce the problem, add some loops to get some combinatory, then check the result. This drastically cuts down on the time spent on debugging my module (or the modules used by it, for that matter :)
Pros:
- SWIG: Relatively easy generation of stub code (by using interface files)
- SWIG: It is possible to use the same interface files to generate stub code for Java, Python (though, I didn't test this feature)
- SWIG: Excellent doc.
- Perl: you can leverage the CPAN/PPM modules to do some truly magical hackings
Cons:Summary: If you are a C/C++ developper and your code can use XML/text files/strings, consider using SWIG or XS for testing purpose.
PS: if you want to Quantify/Purify your module/Perl script, using ActiveState Perl, you need to recompile Perl with the -DPURIFY option toggled on.
I'm just waiting for someone... (Score:1)
The trouble with mixed-language work (Score:3, Informative)
The result, of course, is undebuggable random crashes in the high-level part of the system. Here's are some typical bug reports from mixed Perl/C work:
-
#1 [www.ecos.de]
Okay, it seems to be some kind of conflict between mod_perl/Embperl and PHP and
perhaps Apache::DBI. My Embperl stuff works if there's no database access. It
also works if I don't load libphp4.so. I guess the best solution is to either
build everything statically or run seperate servers for PHP and mod_perl.
-
#2: [openldap.org] Following a large number of updates to our database, slapd is prone to crashing
when reading values back. We load a database of about 3800 users with slapadd,
then modify a single attribute of every 'person'. Then slapd is likely to
crash
on reading values back. Restarting slapd seems to make it work again. Just
prior
to the crash, slapd will give incorrect query results.
... We have a large client site limping along due to this kind of problem ... so any
help would be welcome.
After this, you begin to understand the logic behind Microsoft's C# mixed-language run-time environment. That's ugly, too, but more maintainable, because the toolset has some support for mixed-language work.I'd like to see safe inter-language calls across a protection boundary. CORBA is about as good as it gets, but it's slow, because it marshalls the data into a stream and pumps it through a socket to the other side. There are faster approaches (look at Multics protection rings) but they need some hardware support, which we don't have today.
Re:The trouble with mixed-language work (Score:2)
As long as you have two rings, you can emulate an infinate number of rings. x86 CPUs have 4 rings...
Of course, MS is never going to put in the kernel code to have the MULTICS 32 rings on x86...
On the other hand, you can use L4 IPC and something that's CORBA-like. But then you'd be limited to native L4 binaries and Linux binaries. (And last I cecked, the latest kernel ported as an L4 server was a 2.2 kernel.)
Re:The trouble with mixed-language work (Score:2)
This is a bit offtopic, but to answer the previous question...
Basically, to do CORBA-like operations fast, you need to pass a portion of the stack across a protection boundary. Part of the stack should be read-write, part should be read-only, and most should be inaccessable. In addition, you need a way to pass descriptors of memory areas (i.e. segment descriptors) across. Seldom are more than one or two such segments required.
I once looked into using the call gate machinery on x86 machines and the L4 object model to implement safe calling between mutually mistrustful objects along the above lines. It can almost work, but the hardware doesn't quite do the right thing. The ring machinery basically assumes that one side is more trusted than the other. It's not peer to peer. Very frustrating. It's really close to what you need, but not quite there.
Without hardware support, you need to do copying. And on most popular operating systems, too much copying. What you want is a subroutine call across address spaces, but what the OS usually gives you is an I/O operation. QNX is one of the few major exceptions, and even QNX has to do copying of messages. But QNX has very low overhead for interprocess message passing, and everything else uses that primitive. That's the right approach when you really need it to work.
Understand, there's no problem doing this stuff either insecurely or slowly. But fast (without a trip through the kernel every time) and secure (one side can't clobber the other's memory) requires some hardware assistance. So few programs are architected that way.
Tcl and other languages (Score:2, Informative)
Perl, IMO, is the worst of the scripting languages to combine with C... the interface is not pretty. Other languages like Python aren't bad. Lua is good if you want something really small and fast.
Re:Tcl and other languages (Score:1)
Why do we need comparisons? (Score:3, Interesting)
problems learning Perl, but I always thought
it's more fun to learn new way of thinking
that comes with a new language. Thinking
of a new language in terms of the one you
know may result in taking the old-language
style of programming to the new one - so
what's the point of learning?
You can probably explain LISP in terms of Basic
concepts, but that's a waste...
Next: Extending and Embracing Perl (Score:1, Funny)
Right stuff (Score:2)
But for code that calculates my taxes or bank balance, or drives the displays at the operating theatre if I'm brought in for emergency heart surgery, I want implementation languages where there is no question of ambiguity in the interpretation of the semantics of the code.
--
Perl, C, C++ (urgh) hacker. Don't tell anyone I can read COBOL.
Not intended as a flamebait, but... (Score:1)
Open(file) OR Die
???
Thanks.
Re:Not intended as a flamebait, but... (Score:1)
Try reading it out loud. It's only slightly more nonsense than English. (Perl's case-sensitive, though, so I'm assuming you've provided pseudo-Perl.)
Re:Not intended as a flamebait, but... (Score:1)
So my original question remains: Why is this a good thing?
Re:Not intended as a flamebait, but... (Score:2, Informative)
It's a good thing, according to Larry, because Perl more closely maps to spoken language patterns. His theory is that the computer should do extra work to make the life of a programmer easier.
I don't understand your comment about interpreting that code as a boolean construct. That's exactly how Perl does evaluate it. See B::Deparse for clarification.
Re:Not intended as a flamebait, but... (Score:1)
But if you like it, you like it I guess..
Thanks.
Re:Not intended as a flamebait, but... (Score:1)
one example of how to do it (Score:1)
This game does all the code in perl using the SDL perl bindings [sdlperl.org] (which makes the code as short as possible and easy to change) with special effects written in C (.xs file). Works like a breeze (besides it's addictive).
Re:What's with the Related Links? (Score:1)
Re:What's with the Related Links? (Score:2, Informative)
Re:Perl: Fitting into the Big Picture (Score:2)
open platforms.
Re:Perl: Fitting into the Big Picture (Score:2, Funny)
When that happens it will be just about time for the second coming!
Re:Perl: Fitting into the Big Picture (Score:5, Informative)
Uh, no. Thanks for playing. There are things that C++ does that Java does not -- some of which I'm thankful do not exist in Java (preprocessor) and some of which I miss (generics). But despite its C-like syntax and superficial resemblances (finalizers seem like destructors but aren't) Java is more like Smalltalk than C++.
Take a quick gander the section For C, C++ Fans [sun.com] in Peter van der Linden's Java Programmers FAQ [afu.com]
But then, why am I arguing over the relative merits of Perl, Java, C++, and C# with a user having the handle "Microsoft Research" who posts pure FUD?
Re:Perl: Fitting into the Big Picture (Score:1, Interesting)
System-level languages: C, C++. If you want to write an OS, or a native object library or executable, you'll probably use one of these.
Rapid prototyping and non-expert programming: a weakly-typed script language, such as Python. Here, bindings to any native object (as in code, not oriented) library can be provided for things such as OS interfaces, GUI class libraries, application specific APIs, etc. If you want to provide a command-oriented interface (as opposed to function-call-like syntax), you might choose Tcl instead.
Random data hacking: it really doesn't matter. Perl seems popular, but also sh/grep/sed/awk still works (and it can be done in Python as well). If you're not on an "open-source platform" you'll probably find no native tools for this and will wind up installing Perl or something similar, although you'll find the command-line painfully hard to use.
So then the question is: where to Java, C#, Basic and Lisp fit in. Nowhere, really. Java and C# were invented by Sun and Microsoft to take market share from one another. If you have a choice, it isn't clear why you'd use them because they offer all of the complexity of C++ with only the minimal benefit of taking care of some memory management issues. However, you may be forced to use one of these languages because the bindings to the libraries you want are only available there. There is likely no technical reason for this, only a marketing reason. As for Basic and Lisp, they are just old solutions to the rapid prototyping problem, and should be replaced with modern languages.
IMO, that's the way it is.
Re: (Score:1)