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Write Portable Code
Simon P. Chappell writes "Much as a certain large software company located in the North-West of the United States of America might wish otherwise, there are many different operating systems and platforms in use in the world today. Software these days needs to able to operate in a disparate environment, either by communicating with these other platforms or by running on them or, increasingly, doing both. The Information Systems industry is making good progress with the communication half of the problem (even if a lot of it seems to involve large amounts of XML), but it is still struggling with the issues inherent with writing portable code. Brian Hook's contribution to all of this is Write Portable Code , which according to it's subtitle is an introduction to developing software for multiple platforms." Read on for the rest of Simon's review.
Write Portable Code
author
Brian Hook
pages
248 (14 page index)
publisher
No Starch Press
rating
8/10
reviewer
Simon P. Chappell
ISBN
1593270569
summary
I recommend this book to anyone working with portable code.
This is a book for computer programmers who write software designed to run on multiple platforms. It's also for programmers who suspect that their software may need to run on different platforms. This brings the book onto the radar for free and open source software authors, as they seek to create software that does not trap their end users into using specific operating systems. The Structure
There is a good progression shown in the eighteen chapters of the book. The first couple of chapters introduce the reader to portability concepts and then to some of the specific portability features of ANSI C and C++ that are used throughout the rest of the book.
The middle chapters of the book, cover individual portability topics. Some of these topics are the obvious ones, like Floating Point numbers, Networking, Operating System, File System and Dynamic Libraries. Other topics are less intuitively associated with portability, but when you read the chapter, it's inclusion is both obvious and necessary. These subjects include Source Code Management, Compilers, Scalability and Data. There is more to portability than many of us might suspect.
The last two chapters look at some alternative ways of getting portability. Scripting languages are discussed and the pros and cons of each ones portability is weighed. Lastly the use of cross-platform libraries and toolkits is addressed. Quite apropos given that the book's author is also the author of a cross platform library.
As an example of the thoughtful approach taken in this book, lets' take a look at the chapter on scripting languages. It's about the shortest chapter in the book, but representative of the approach that Mr. Hook brings to his work. This chapter takes a very honest look at the portability and cross-platform aspects of using scripting languages. There are advantages and disadvantages to the use of scripting languages. The advantages include everything that is a disadvantage of low-level languages like C/C++. Scripting languages do not require you to worry about about memory allocation, bindings, System API calls or any of the other bugbears of a low-level language programmer's life. The disadvantages of scripting languages naturally include performance, given their interpreted natures, a general lack of tools, such as development environments or IDEs and their tendency to sit high above the operating system with a corresponding detachment from low-level facilities and services of that same operating system. Mr. Hook's choice of scripting languages to consider was interesting. I expected Ruby and Python; both popular and capable in their own right. The inclusion of JavaScript/ECMAScript was also not too unexpected, now that standalone versions are bubbling up and becoming available. The real surprise, albeit a pleasant one, was the inclusion of Lua; a scripting language designed for platform portability and which seems to have managed to fully mature without making a blip on most geeks radar screens.
I like that Mr. Hook has experience writing portable software. This matched with his authorship of the Portable Open Source Harness (POSH) portability library and his contributions to the Simple Audio Library (SAL) gives a great deal of credence to his writing.
This is a solid "doing" book. Mr. Hook is under no illusion that he's writing an introduction to programming. This book has a consistent purpose to take experienced programmers and fully equip them to deal with portability and it does not deviate from this in the slightest.
The layout of the book is first rate, with clear typography, comfortable spacing, clear diagrams and tables and nicely highlighted callouts. I did not notice any obvious typos or glitches in the book. While the look of a book is not the author's fault if it is below par, a well presented book can enhance the reading and learning experience.
The examples are as realistic as possible. While some of the examples to teach principles might be simpler, they are typically backed up with examples from either the POSH or SAL projects, showing real world portability coding. The level of C/C++ required to understand the examples is higher than many books that I've read. That's not to say that the code seems obfuscated, but it's code that is taking into account aspects of the real world and is, by necessity, not simple. A further positive quality of the code examples is that they're very well explained; well enough that an inexperienced programmer with determination could follow them and come to an understanding.
Appendix B contains a summary of all of the portability rules presented through the book. There are twenty rules and each is reprised with a small explanation/reminder of it's application. An example: Rule 4 - "Never read or write structures monolithically from or to memory. Always read and write structures one element at a time, so that endian, alignment, and size differences are factored out."
If you're looking for more of a fluffy "about" book, then this is not it. This is not a complaint, rather I offer it as something to consider, before you buy what you might otherwise think is a beginner's book.
I must reiterate the non-trivial C/C++ example code the book contains. This book is for serious programmers and is not afraid to role up it's sleeves and cut real code.
This is a very well written and very readable book. There are many aspects to the subject matter of portability and Mr. Hook addresses more of them than many of us had previously suspected existed and addresses them with firm authority. I recommend this book to anyone working with portable code."
You can purchase Write Portable Code from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
This is a book for computer programmers who write software designed to run on multiple platforms. It's also for programmers who suspect that their software may need to run on different platforms. This brings the book onto the radar for free and open source software authors, as they seek to create software that does not trap their end users into using specific operating systems. The Structure
There is a good progression shown in the eighteen chapters of the book. The first couple of chapters introduce the reader to portability concepts and then to some of the specific portability features of ANSI C and C++ that are used throughout the rest of the book.
The middle chapters of the book, cover individual portability topics. Some of these topics are the obvious ones, like Floating Point numbers, Networking, Operating System, File System and Dynamic Libraries. Other topics are less intuitively associated with portability, but when you read the chapter, it's inclusion is both obvious and necessary. These subjects include Source Code Management, Compilers, Scalability and Data. There is more to portability than many of us might suspect.
The last two chapters look at some alternative ways of getting portability. Scripting languages are discussed and the pros and cons of each ones portability is weighed. Lastly the use of cross-platform libraries and toolkits is addressed. Quite apropos given that the book's author is also the author of a cross platform library.
As an example of the thoughtful approach taken in this book, lets' take a look at the chapter on scripting languages. It's about the shortest chapter in the book, but representative of the approach that Mr. Hook brings to his work. This chapter takes a very honest look at the portability and cross-platform aspects of using scripting languages. There are advantages and disadvantages to the use of scripting languages. The advantages include everything that is a disadvantage of low-level languages like C/C++. Scripting languages do not require you to worry about about memory allocation, bindings, System API calls or any of the other bugbears of a low-level language programmer's life. The disadvantages of scripting languages naturally include performance, given their interpreted natures, a general lack of tools, such as development environments or IDEs and their tendency to sit high above the operating system with a corresponding detachment from low-level facilities and services of that same operating system. Mr. Hook's choice of scripting languages to consider was interesting. I expected Ruby and Python; both popular and capable in their own right. The inclusion of JavaScript/ECMAScript was also not too unexpected, now that standalone versions are bubbling up and becoming available. The real surprise, albeit a pleasant one, was the inclusion of Lua; a scripting language designed for platform portability and which seems to have managed to fully mature without making a blip on most geeks radar screens.
I like that Mr. Hook has experience writing portable software. This matched with his authorship of the Portable Open Source Harness (POSH) portability library and his contributions to the Simple Audio Library (SAL) gives a great deal of credence to his writing.
This is a solid "doing" book. Mr. Hook is under no illusion that he's writing an introduction to programming. This book has a consistent purpose to take experienced programmers and fully equip them to deal with portability and it does not deviate from this in the slightest.
The layout of the book is first rate, with clear typography, comfortable spacing, clear diagrams and tables and nicely highlighted callouts. I did not notice any obvious typos or glitches in the book. While the look of a book is not the author's fault if it is below par, a well presented book can enhance the reading and learning experience.
The examples are as realistic as possible. While some of the examples to teach principles might be simpler, they are typically backed up with examples from either the POSH or SAL projects, showing real world portability coding. The level of C/C++ required to understand the examples is higher than many books that I've read. That's not to say that the code seems obfuscated, but it's code that is taking into account aspects of the real world and is, by necessity, not simple. A further positive quality of the code examples is that they're very well explained; well enough that an inexperienced programmer with determination could follow them and come to an understanding.
Appendix B contains a summary of all of the portability rules presented through the book. There are twenty rules and each is reprised with a small explanation/reminder of it's application. An example: Rule 4 - "Never read or write structures monolithically from or to memory. Always read and write structures one element at a time, so that endian, alignment, and size differences are factored out."
If you're looking for more of a fluffy "about" book, then this is not it. This is not a complaint, rather I offer it as something to consider, before you buy what you might otherwise think is a beginner's book.
I must reiterate the non-trivial C/C++ example code the book contains. This book is for serious programmers and is not afraid to role up it's sleeves and cut real code.
This is a very well written and very readable book. There are many aspects to the subject matter of portability and Mr. Hook addresses more of them than many of us had previously suspected existed and addresses them with firm authority. I recommend this book to anyone working with portable code."
You can purchase Write Portable Code from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
and this is why web applications are becoming so popular...it's much easier to make something written in PHP and distributed through the web available to everyone than to try to port something in C++ across a bunch of platforms. imho this trend towards AJAX and more web applications is a good thing and makes it easier on developers trying to deal with clients on multiple platforms. i don't want to have to deal with porting applications (although cross-browser compatibilities offer their own complications).
How can I write portable versions of Mac OS X apps when the Cocoa API doesn't exist outside of Mac OS X (don't tell me about YellowBox or what-have-you) and the language Objective C isn't supported outside of Mac OS X (Apple is killing off Cocoa's Java support)? Oh, and the Carbon API doesn't exist outside of Mac OS X either (but at least it uses a widely supported language). You mentioned a software company in the Northwest US, but what about the one in Cupertino? Apps written to their platform are no more portable than Windows apps.
Besides that, apps that aren't able to take advantave of the underlying platform's unique features aren't sellable. Mac users in particular want apps that take advantage of the unique features of Mac OS X (and no, they don't consider some unix app to be a real "Mac" app, and rightly so). That means Cocoa or Carbon, and neither api is supported outside of Mac OS X.
-- "I never gave these stories much credence." - HAL 9000
"as a certain large software company located in the North-West of the United States of America might wish otherwise, there are many different operating systems and platforms in use in the world today. "
If his first sentence isn't trolling I don't know what is. Why is it ok to do it against MS, but nobody else?
You do it against MS, you make the front page, against apple you get flamed.
I got my first job and started digging into some code that was written for portability, it all seemed so obfuscated.
I was like, "Why are they #defining all their data types to something else? And what's with all the crazy compiler directives?" It seemed like they were going out of their way to make the code less readable.
Once I figured out that it was all there so that the code could be recompiled for different platforms, it all clicked together. It's really cool, and I'm pissed that I got out of college not knowing this stuff. It should be a required course, IMHO.
are done w/ J2SE using SWT as the front end. Looks like a native app, runs super fast since it relies on native widgets, and portability issues are largely mitigated for me.
Then device drivers and operating systems were going to let us abstract away the details of the underlying implementation of the hardware, letting us write portable code. But not all O/S versions are compatible; there are glibc issues under Linux, and so on.
Then JAVA was going to be completely portable to all operating systems. But not all Java virtual machines are identical, and different version of Java came out, and things diverged.
All of these things made life more portable, to some degree. All of them still require boostrapping a system that understands the underlying hardware and deals with it efficiently; then abstracts all that hardware specific efficiency away again.
Portability is *hard*: in some sense, it's the enemy of efficiency. You need to abstract away all those nice hardware specifics that make the hardware work, and replace them with a theoretical construct that caters to the lowest common denominator that you're willing to support.
What's worse, as soon as someone makes a different design decision, or an improvement, or something that isn't universally adopted all at once, you have multiple versions -- divergent standards which aren't completely compatible. It happened with UNIX; it's happening with Linux (to a lesser extent, because code can merge again after a fork), and it happened with C and Java.
What can the developer do? Just our best; true universal portability is a Holy Grail that we'll never attain, because the day we do, someone will invent a radical new system that doesn't quite fit our abstraction model...
Amen, brother.
.ini files, or CStrings, or what have you. It was all the non-portable things they did without even knowing it--and the fact that the non-portable stuff was salted and peppered evenly throughout the whole project instead of concentrated in a few well-defined modules--that got to me.
I've been involved in way too many projects where people said, "Oh, yeah, we're doing all our development on Windows but it's no big deal. We aren't going to use anything non-portable."
Then, when the time came to port it... it was utterly intertwingled with Windows-specific cruft, half of which crept in because nobody even knew they were doing it. If they'd ever tried even once to port it, they could have caught this stuff as it happened.
I don't mind a conscious decision to use
And it didn't help that everything was compiled with permissive compiler options regarding C/C++ conformance, and a low warning level.
"How to Do Nothing," kids activities, back in print!
My team's been writing 100% portable C code since 1991 or so. We took the same approach that Apache has done since version 2, i.e. build a distinct portability library and remove all non-portable code from the application itself.
It's amazing anyone would actually write non-portable code except through ignorance. As a programmer, I still run code written in 1991-2 (though it's been marginalised by newer work), and we have made some quite complex products (web servers, code generators) that run on anything that has standard C libraries and BSD-style TCP/IP, including OS/2, OpenVMS, and of course all Unix and Windows boxes.
The alternative option is to use a VM. Since we write fast system software that's not an option.
A wise person taught me this over 20 years ago: life is too short to throw out code just because some platform changed. Portability is one of those skills that lets a normal programmer like me accumulate enough quality code over time to become a master programmer.
My blog
That's right, you heard me. Don't write portable code.
Use portable libraries and languages; re-factor your working code to be portable; make high-level choices that support portability (e.g. don't lock yourself in to proprietary solutions), but don't write portable code.
Why? Because premature portability, like premature optimization is a red herring that steals your attention from the only two things that will ever matter: correctness and maintainability. Write correct code. Write verifiably correct code. Write maintainable code. Do these things and you are done. Then, port it to another platform or ten and optimize the hell out of it. Don't do these things up-front, as they buy you nothing on the first pass, and doing them later will give you the chance to re-consider the structure of your system which you should do at least twice before your first release anyway.
That said, do not snub portability unduely. If you have the choice of trivially supporting or not supporting portability-enhacing features (e.g. in your choice of a configure/build system), there's no reason not to be portable. Just don't let it set priorities for your project from day one.
Write Once Compile Anywhere will never be completely realized since various systems have incompatible design goals. No matter how portable you've made your command line application, it probably won't make a lot of sense on a Palm. That's not a limitation of your code or PalmOS, but an acknowledgment that they're different animals.
Dewey, what part of this looks like authorities should be involved?
> Good Java programmers... use Python instead.
Votez ecolo : Chiez dans l'urne !
I know you're kidding, but unfortunately there are a lot of responses here which indicate that Java is the end-all and be-all of portable programming.
I'm sorry folks. Such people have never done real cross-platform programming. Java simply isn't an option on MANY platforms. If all you do is x86 platforms, and perhaps some Motorola workstation-class platforms, hey, you're fine.
But that's not the real world.
The real world includes MIPS, ARM and other processors. What's more, the embedded world makes up most of the usage of CPU's. Java is not an option in most cases, unless you go out and pay one of the few small shops that will port it a bunch of money. And that assumes your system have the footprint and horsepower to run it.
I see outfits where the programmers have never programmed on a non-x86 system in their life suddenly wake up to this fact. It would be funny if it wasn't so sad.
Now, granted the GNU folks are coming up with their Open Source version, and it appears to be coming along fine. But it's not quite there yet.
Also, keep in mind that it won't run on many platforms, simply because of size limitations. All the world isn't your dual-core 3 GHz x86 with 4 GB of RAM.
And I'm sorry, but the Java claims that it is as fast as C code just aren't true. Don't believe me? Try doing some benchmarks on 100 MHz small-RAM systems. If you're lucky enough to get it to fit, you'll see that things are just dog slow.
Most programmers and students today are just too used to working with the supercomputer type of CPU's that the modern desktop is like, and aren't used to dealing with small-footprint type of systems which make up most of the world
I think all the proponents of Java kind of missed the point here. Not everything has or even NEEDS the level of horsepower that Java requires- and just adding more muscle isn't always in the chips.
And even then, saying "Java" will run everywhere, is really a mis-concept. It'll run most everywhere where there is a least common denominator. I can tell you that while it makes it easier for Oddlabs to make Tribal Trouble for three platforms simultaneously, Java doesn't make it cross-platform- you can't take it and run it on say a Solaris box (though I suspect they could MAKE a Solaris iteration of the game easily enough...) or on an embedded machine using Java, say like the Ignite platform.
Java makes some things "easier" to make cross-platform, but again, it's like anything else- cross-platform is more of a philosophy than a feature set of a language or toolset. And it's definitely NOT the panacea that the proponents in this thread make it out to be- I should know, I do Java development amongst other things. If you can't make a C++ program at least 40% faster than your best Java code, you might want to re-work the C++ code. This is not to say that it's a bad idea or anything; it's just that people keep trying to jam it into problem sets that it's ill suited for.
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