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  • Google Developer Day 2010 - Highlights

    Google Developer Day 2010 - Highlights Highlights from Google Developer Day 2010 in Tokyo, Sao Paulo, Munich, Moscow and Prague. www.google.com All photos & videos at www.google.com Follow us on the Code blog and Twitter to stay updated on developer news: googlecode.blogspot.com http Hashtags: #gdd2010jp #gddbr #gddde #gddru #gddcz From: GoogleDevelopers Views: 2524 48 ratings Time: 02:53 More in Science & Technology

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  • Google Chrome Extensions: UI Design

    Google Chrome Extensions: UI Design Erik Kay, an engineer at Google, provides more information about the UI of Google Chrome's extension system. For more information visit code.google.com/chrome/extensions. From: GoogleDevelopers Views: 10120 57 ratings Time: 03:49 More in Science & Technology

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  • .NET Reflector Pro to the rescue

    Almost all applications have to interface with components or modules written by somebody else, for which you don't have the source code. This is fine until things go wrong, but when you need to refactor your code and you keep getting strange exceptions, you'll start to wish you could place breakpoints in someone else's code and step through it. Now, of course, you can, as Geoffrey Braaf discovered.

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  • Windows Phone 7 Prototype 002: Animated Page Transitions + Writeable Bitmaps

    Motion is a key part of WP7 application development. Without motion, the WP7 UI is just a bunch of text. Not nearly as exciting. To delight users, you can add some transitions between pages.  The sample app includes some storyboards to animate between two pages. Other people have noted that you can just use the transitioning content control form the SIlverlight toolkit. Peter Torr also had a nice animating frame control in his mix demo code (his blog has some other great code samples for WP7 app dev). I took some of those concepts and the code from the TransitioningContentControl to make a new animating frame control. In this prototype, the frame takes a snapshot of the old content and the new content using writeable bitmaps and animates the snapshots and then replaces those with the actual page. The benefit is smoother animation on pages with lots of controls. Otherwise, if you have a large panorama, it might not animate that cleanly.  Like the other solutions based on the TransitioningContentControl, you can centralize all the animations in one place and not have to handle them on each individual page. Peters code also had a nice snippet for choosing the animation based on the navigation direction so you could just have a forward / backward animation and not have to do anything on each page. You could also probably add some more advanced transitions using pixel shaders or make an default no transition state if you wanted to have some specific animation on a page where individual  controls transitioned out differently like some of the WP7 shell apps. Sample Code 100% guaranteed to work on my emulatorDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • YouTube Direct: Getting Started Guide

    YouTube Direct: Getting Started Guide Jeff Posnick narrates a screencast detailing all aspects of getting started with youtube Direct, from required downloads to configuration to deployment. For even more information about youtube Direct, see code.google.com From: GoogleDevelopers Views: 9685 32 ratings Time: 19:58 More in Science & Technology

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  • Google Python Class Day 2 Part 2

    Google Python Class Day 2 Part 2 Google Python Class Day 2 Part 2: Utilities: OS and Commands. By Nick Parlante. Support materials and exercises: code.google.com From: GoogleDevelopers Views: 11 1 ratings Time: 20:20 More in Science & Technology

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  • .NET 4: &ldquo;Slim&rdquo;-style performance boost!

    - by Vitus
    RTM version of .NET 4 and Visual Studio 2010 is available, and now we can do some test with it. Parallel Extensions is one of the most valuable part of .NET 4.0. It’s a set of good tools for easily consuming multicore hardware power. And it also contains some “upgraded” sync primitives – Slim-version. For example, it include updated variant of widely known ManualResetEvent. For people, who don’t know about it: you can sync concurrency execution of some pieces of code with this sync primitive. Instance of ManualResetEvent can be in 2 states: signaled and non-signaled. Transition between it possible by Set() and Reset() methods call. Some shortly explanation: Thread 1 Thread 2 Time mre.Reset(); mre.WaitOne(); //code execution 0 //wating //code execution 1 //wating //code execution 2 //wating //code execution 3 //wating mre.Set(); 4 //code execution //… 5 Upgraded version of this primitive is ManualResetEventSlim. The idea in decreasing performance cost in case, when only 1 thread use it. Main concept in the “hybrid sync schema”, which can be done as following:   internal sealed class SimpleHybridLock : IDisposable { private Int32 m_waiters = 0; private AutoResetEvent m_waiterLock = new AutoResetEvent(false);   public void Enter() { if (Interlocked.Increment(ref m_waiters) == 1) return; m_waiterLock.WaitOne(); }   public void Leave() { if (Interlocked.Decrement(ref m_waiters) == 0) return; m_waiterLock.Set(); }   public void Dispose() { m_waiterLock.Dispose(); } } It’s a sample from Jeffry Richter’s book “CLR via C#”, 3rd edition. Primitive SimpleHybridLock have two public methods: Enter() and Leave(). You can put your concurrency-critical code between calls of these methods, and it would executed in only one thread at the moment. Code is really simple: first thread, called Enter(), increase counter. Second thread also increase counter, and suspend while m_waiterLock is not signaled. So, if we don’t have concurrent access to our lock, “heavy” methods WaitOne() and Set() will not called. It’s can give some performance bonus. ManualResetEvent use the similar idea. Of course, it have more “smart” technics inside, like a checking of recursive calls, and so on. I want to know a real difference between classic ManualResetEvent realization, and new –Slim. I wrote a simple “benchmark”: class Program { static void Main(string[] args) { ManualResetEventSlim mres = new ManualResetEventSlim(false); ManualResetEventSlim mres2 = new ManualResetEventSlim(false);   ManualResetEvent mre = new ManualResetEvent(false);   long total = 0; int COUNT = 50;   for (int i = 0; i < COUNT; i++) { mres2.Reset(); Stopwatch sw = Stopwatch.StartNew();   ThreadPool.QueueUserWorkItem((obj) => { //Method(mres, true); Method2(mre, true); mres2.Set(); }); //Method(mres, false); Method2(mre, false);   mres2.Wait(); sw.Stop();   Console.WriteLine("Pass {0}: {1} ms", i, sw.ElapsedMilliseconds); total += sw.ElapsedMilliseconds; }   Console.WriteLine(); Console.WriteLine("==============================="); Console.WriteLine("Done in average=" + total / (double)COUNT); Console.ReadLine(); }   private static void Method(ManualResetEventSlim mre, bool value) { for (int i = 0; i < 9000000; i++) { if (value) { mre.Set(); } else { mre.Reset(); } } }   private static void Method2(ManualResetEvent mre, bool value) { for (int i = 0; i < 9000000; i++) { if (value) { mre.Set(); } else { mre.Reset(); } } } } I use 2 concurrent thread (the main thread and one from thread pool) for setting and resetting ManualResetEvents, and try to run test COUNT times, and calculate average execution time. Here is the results (I get it on my dual core notebook with T7250 CPU and Windows 7 x64): ManualResetEvent ManualResetEventSlim Difference is obvious and serious – in 10 times! So, I think preferable way is using ManualResetEventSlim, because not always on calling Set() and Reset() will be called “heavy” methods for working with Windows kernel-mode objects. It’s a small and nice improvement! ;)

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  • fsockopen() error : Network is unreachable port 43 in php [closed]

    - by hamid
    i've writed some Php code that lookup for domain (whois) but it fails !! this is some of my code : function checkdomain($server,$domain){ global $response; $connection = fsockopen($server,43); fputs($connection, "domain " . $domain . "\r\n"); while(!feof($connection)){ $response .= fgets($connection, 4096); } fclose($connection); } checkdomain("whois.crsnic.net","www.example.com"); the code work on my localhost ( apache,php,mysql, OS - Win XP ) but when i uploaded it to my host (Linux) it failed. and i always see the Below Error/message : Warning: fsockopen() [function.fsockopen]: unable to connect to whois.crsnic.net:43 (Network is unreachable) in /home/hamid0011/public_html/whois/whois.php on line 37 what should i do ? is this my host's problem or whois server ( but it work in localhost ) or my code ? TNX

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  • Google Chrome Extensions: Identity, Signing and Auto Update

    Google Chrome Extensions: Identity, Signing and Auto Update Antony Sargent, a software engineer at Google discusses topics related to ids, packaging and distribution of extensions in the Google Chrome Extension system. To get more information, visit code.google.com/chrome/extensions From: GoogleDevelopers Views: 27337 54 ratings Time: 04:08 More in Science & Technology

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  • Generating a Google Drive Hosted Website with tools you have lying around in your kitchen

    Generating a Google Drive Hosted Website with tools you have lying around in your kitchen Now that you can host web content in Google Drive, Ali will take a look at writing some code to generate a website from files stored in Google Drive. This should be a fun session, and as will all live coding, totally able to fail in about a million ways. From: GoogleDevelopers Views: 0 0 ratings Time: 03:30:00 More in Science & Technology

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  • Google Chrome Extensions Developer Snapshots - Web of Trust

    Google Chrome Extensions Developer Snapshots - Web of Trust Deborah Salmi, CMO of WOT (www.mywot.com) discusses her company's experience with the Google Chrome extensions platform. To learn more on creating Google Chrome Extensions please visit code.google.com/chrome/extensions or chek out the gallery at chrome.google.com/extensions. From: GoogleDevelopers Views: 5 0 ratings Time: 05:39 More in Science & Technology

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  • Is it bad to have an "Obsessive Refactoring Disorder"?

    - by Rachel
    I was reading this question and realized that could almost be me. I am fairly OCD about refactoring someone else's code when I see that I can improve it. For example, if the code contains duplicate methods to do the same thing with nothing more than a single parameter changing, I feel I have to remove all the copy/paste methods and replace it with one generic one. Is this bad? Should I try and stop? I try not to refactor unless I can actually make improvements to the code performance or readability, or if the person who did the code isn't following our standard naming conventions (I hate expecting a variable to be local because of the naming standard, only to discover it is a global variable which has been incorrectly named)

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  • Google I/O 2010 - Developing web apps for Chrome Web Store

    Google I/O 2010 - Developing web apps for Chrome Web Store Google I/O 2010 - Developing web apps for the Chrome Web Store Chrome 101 Erik Kay Google Chrome is a powerful platform for developing web apps. With Chrome web apps, we're making it easier for users to discover and use these apps. Learn how to build and sell apps for the Chrome Web Store. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 8 0 ratings Time: 01:00:29 More in Science & Technology

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  • SharePoint Web Part Constructor Fires Twice When Adding it to the Page (and has a different security

    - by Damon
    We had some exciting times debugging an interesting issue with SharePoint 2007 Web Parts.  We had some code in staging that had been running just fine for weeks and had not been touched or changed in about the same amount of time.  However, when we tried to move the web part into a different staging environment, the part started throwing a security exception when we tried to add it to a page.  After a bit of debugging, we determined that the web part was throwing the exception while trying to access the SPGroups property on the SharePoint site.  This was pretty strange because we were logged in as an admin and the code was working perfectly fine before.  During the debugging process, however, we found out that the web part constructor was being fired twice.  On one request, the security context did not seem to have everything it needed in order to run.  On the other request, the security context was populated with the user context with the user making the request (like it normally is).  Moving the security code outside of the constructor seems to have fixed the issue. Why the discrepancy between the two staging environments?  Turns out we deployed the part originally, then deployed an update with the security code.  Since the part was never "added" to the page after the code updates were made (we just deployed a new assembly to make the updates), we never saw the problem.  It seems as though the constructor fires twice when you are adding the web part to the page, and when you run the web part from the web part gallery.  My only thought on why this would occur is that SharePoint is instantiating an instance to get some information from it - which is odd because you would think that would happen with reflection without requiring a new object.  Anyway, the work around is to just not put anything security related inside the constructor, or to do a good job accounting for the possibility of the security context not being present if you are adding the item to the page. Technorati Tags: SharePoint,.NET,Microsoft,ASP.NET

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  • Beginner's guide to writing comments?

    - by Cameron
    Is there a definitive guide to writing code comments, aimed at budding developers? Ideally, it would cover when comments should (and should not) be used, and what comments should contain. This answer: Do not comment WHAT you are doing, but WHY you are doing it. The WHAT is taken care of by clean, readable and simple code with proper choice of variable names to support it. Comments show a higher level structure to the code that can't be (or is hard to) show by the code itself. comes close, but it's a little concise for inexperienced programmers (an expansion on that with several examples and corner cases would be excellent, I think).

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  • Style bits vs. Separate bool's

    - by peterchen
    My main platform (WinAPI) still heavily uses bits for control styles etc. (example). When introducing custom controls, I'm permanently wondering whether to follow that style or rather use individual bool's. Let's pit them against each other: enum EMyCtrlStyles { mcsUseFileIcon = 1, mcsTruncateFileName = 2, mcsUseShellContextMenu = 4, }; void SetStyle(DWORD mcsStyle); void ModifyStyle(DWORD mcsRemove, DWORD mcsAdd); DWORD GetStyle() const; ... ctrl.SetStyle(mcsUseFileIcon | mcsUseShellContextMenu); vs. CMyCtrl & SetUseFileIcon(bool enable = true); bool GetUseFileIcon() const; CMyCtrl & SetTruncteFileName(bool enable = true); bool GetTruncteFileName() const; CMyCtrl & SetUseShellContextMenu(bool enable = true); bool GetUseShellContextMenu() const; ctrl.SetUseFileIcon().SetUseShellContextMenu(); As I see it, Pro Style Bits Consistent with platform less library code (without gaining complexity), less places to modify for adding a new style less caller code (without losing notable readability) easier to use in some scenarios (e.g. remembering / transferring settings) Binary API remains stable if new style bits are introduced Now, the first and the last are minor in most cases. Pro Individual booleans Intellisense and refactoring tools reduce the "less typing" effort Single Purpose Entities more literate code (as in "flows more like a sentence") No change of paradim for non-bool properties These sound more modern, but also "soft" advantages. I must admit the "platform consistency" is much more enticing than I could justify, the less code without losing much quality is a nice bonus. 1. What do you prefer? Subjectively, for writing the library, or for writing client code? 2. Any (semi-) objective statements, studies, etc.?

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  • Google Python Class Day 1 Part 1

    Google Python Class Day 1 Part 1 Google Python Class Day 1 Part 1: Introduction and Strings. By Nick Parlante. Support materials and exercises: code.google.com From: GoogleDevelopers Views: 137 1 ratings Time: 51:37 More in Science & Technology

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  • Google I/O 2010 - Integrate apps w/ Google Apps Marketplace

    Google I/O 2010 - Integrate apps w/ Google Apps Marketplace Google I/O 2010 - Integrating your app with the Google Apps Marketplace: Navigation, SSO, Data APIs and manifests Enterprise 201 Ryan Boyd, Steve Bazyl In this fast-paced, demo-focused session, you'll learn how to build, integrate, and sell a web app on the Google Apps Marketplace. We'll go end-to-end in 40 minutes with time left for Q&A. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 5 0 ratings Time: 59:45 More in Science & Technology

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  • How to use shared_ptr for COM interface pointers

    - by Seefer
    I've been reading about various usage advice relating to the new c++ standard smart pointers unique_ptr, shared_ptr and weak_ptr and generally 'grok' what they are about when I'm writing my own code that declares and consumes them. However, all the discussions I've read seem restricted to this simple usage situation where the programmer is using smart in his/her own code, with no real discussion on techniques when having to work with libraries that expect raw pointers or other types of 'smart pointers' such as COM interface pointers. Specifically I'm learning my way through C++ by attempting to get a standard Win32 real-time game loop up and running that uses Direct2D & DirectWrite to render text to the display showing frames per second. My first task with Direct2D is in creating a Direct2D Factory object with the following code from the Direct2D examples on MSDN: ID2D1Factory* pD2DFactory = nullptr; HRESULT hr = D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &pD2DFactory); pD2DFactory is obviously an 'out' parameter and it's here where I become uncertain how to make use of smart pointers in this context, if indeed it's possible. My inexperienced C++ mind tells me I have two problems: With pD2DFactory being a COM interface pointer type, how would smart_ptr work with the Add() / Release() member functions for a COM object instance? Are smart pointers able to be passed to functions in situations where the function is using an 'out' pointer parameter technique? I did experiment with the alternative of using _com_ptr_t in the comip.h header file to help with pointer lifetime management and declared the pD2DFactory pointer with the following code: _com_ptr_t<_com_IIID<pD2DFactory, &__uuidof(pD2DFactory)>> pD2DFactory = nullptr; and it appears to work so far but, as you can see, the syntax is cumbersome :) So, I was wondering if any C++ gurus here could confirm whether smart pointers are able to help in cases like this and provide examples of usage, or point me to more in-depth discussions of smart pointer usage when needing to work with other code libraries that know nothing of them. Or is it simply a case of my trying to use the wrong tool for the job? :)

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  • Sort Data in Windows Phone using Collection View Source

    - by psheriff
    When you write a Windows Phone application you will most likely consume data from a web service somewhere. If that service returns data to you in a sort order that you do not want, you have an easy alternative to sort the data without writing any C# or VB code. You use the built-in CollectionViewSource object in XAML to perform the sorting for you. This assumes that you can get the data into a collection that implements the IEnumerable or IList interfaces.For this example, I will be using a simple Product class with two properties, and a list of Product objects using the Generic List class. Try this out by creating a Product class as shown in the following code:public class Product {  public Product(int id, string name)   {    ProductId = id;    ProductName = name;  }  public int ProductId { get; set; }  public string ProductName { get; set; }}Create a collection class that initializes a property called DataCollection with some sample data as shown in the code below:public class Products : List<Product>{  public Products()  {    InitCollection();  }  public List<Product> DataCollection { get; set; }  List<Product> InitCollection()  {    DataCollection = new List<Product>();    DataCollection.Add(new Product(3,        "PDSA .NET Productivity Framework"));    DataCollection.Add(new Product(1,        "Haystack Code Generator for .NET"));    DataCollection.Add(new Product(2,        "Fundamentals of .NET eBook"));    return DataCollection;  }}Notice that the data added to the collection is not in any particular order. Create a Windows Phone page and add two XML namespaces to the Page.xmlns:scm="clr-namespace:System.ComponentModel;assembly=System.Windows"xmlns:local="clr-namespace:WPSortData"The 'local' namespace is an alias to the name of the project that you created (in this case WPSortData). The 'scm' namespace references the System.Windows.dll and is needed for the SortDescription class that you will use for sorting the data. Create a phone:PhoneApplicationPage.Resources section in your Windows Phone page that looks like the following:<phone:PhoneApplicationPage.Resources>  <local:Products x:Key="products" />  <CollectionViewSource x:Key="prodCollection"      Source="{Binding Source={StaticResource products},                       Path=DataCollection}">    <CollectionViewSource.SortDescriptions>      <scm:SortDescription PropertyName="ProductName"                           Direction="Ascending" />    </CollectionViewSource.SortDescriptions>  </CollectionViewSource></phone:PhoneApplicationPage.Resources>The first line of code in the resources section creates an instance of your Products class. The constructor of the Products class calls the InitCollection method which creates three Product objects and adds them to the DataCollection property of the Products class. Once the Products object is instantiated you now add a CollectionViewSource object in XAML using the Products object as the source of the data to this collection. A CollectionViewSource has a SortDescriptions collection that allows you to specify a set of SortDescription objects. Each object can set a PropertyName and a Direction property. As you see in the above code you set the PropertyName equal to the ProductName property of the Product object and tell it to sort in an Ascending direction.All you have to do now is to create a ListBox control and set its ItemsSource property to the CollectionViewSource object. The ListBox displays the data in sorted order by ProductName and you did not have to write any LINQ queries or write other code to sort the data!<ListBox    ItemsSource="{Binding Source={StaticResource prodCollection}}"   DisplayMemberPath="ProductName" />SummaryIn this blog post you learned that you can sort any data without having to change the source code of where the data comes from. Simply feed the data into a CollectionViewSource in XAML and set some sort descriptions in XAML and the rest is done for you! This comes in very handy when you are consuming data from a source where the data is given to you and you do not have control over the sorting.NOTE: You can download this article and many samples like the one shown in this blog entry at my website. http://www.pdsa.com/downloads. Select “Tips and Tricks”, then “Sort Data in Windows Phone using Collection View Source” from the drop down list.Good Luck with your Coding,Paul Sheriff** SPECIAL OFFER FOR MY BLOG READERS **We frequently offer a FREE gift for readers of my blog. Visit http://www.pdsa.com/Event/Blog for your FREE gift!

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  • Nagging As A Strategy For Better Linking: -z guidance

    - by user9154181
    The link-editor (ld) in Solaris 11 has a new feature that we call guidance that is intended to help you build better objects. The basic idea behind guidance is that if (and only if) you request it, the link-editor will issue messages suggesting better options and other changes you might make to your ld command to get better results. You can choose to take the advice, or you can disable specific types of guidance while acting on others. In some ways, this works like an experienced friend leaning over your shoulder and giving you advice — you're free to take it or leave it as you see fit, but you get nudged to do a better job than you might have otherwise. We use guidance to build the core Solaris OS, and it has proven to be useful, both in improving our objects, and in making sure that regressions don't creep back in later. In this article, I'm going to describe the evolution in thinking and design that led to the implementation of the -z guidance option, as well as give a brief description of how it works. The guidance feature issues non-fatal warnings. However, experience shows that once developers get used to ignoring warnings, it is inevitable that real problems will be lost in the noise and ignored or missed. This is why we have a zero tolerance policy against build noise in the core Solaris OS. In order to get maximum benefit from -z guidance while maintaining this policy, I added the -z fatal-warnings option at the same time. Much of the material presented here is adapted from the arc case: PSARC 2010/312 Link-editor guidance The History Of Unfortunate Link-Editor Defaults The Solaris link-editor is one of the oldest Unix commands. It stands to reason that this would be true — in order to write an operating system, you need the ability to compile and link code. The original link-editor (ld) had defaults that made sense at the time. As new features were needed, command line option switches were added to let the user use them, while maintaining backward compatibility for those who didn't. Backward compatibility is always a concern in system design, but is particularly important in the case of the tool chain (compilers, linker, and related tools), since it is a basic building block for the entire system. Over the years, applications have grown in size and complexity. Important concepts like dynamic linking that didn't exist in the original Unix system were invented. Object file formats changed. In the case of System V Release 4 Unix derivatives like Solaris, the ELF (Extensible Linking Format) was adopted. Since then, the ELF system has evolved to provide tools needed to manage today's larger and more complex environments. Features such as lazy loading, and direct bindings have been added. In an ideal world, many of these options would be defaults, with rarely used options that allow the user to turn them off. However, the reality is exactly the reverse: For backward compatibility, these features are all options that must be explicitly turned on by the user. This has led to a situation in which most applications do not take advantage of the many improvements that have been made in linking over the last 20 years. If their code seems to link and run without issue, what motivation does a developer have to read a complex manpage, absorb the information provided, choose the features that matter for their application, and apply them? Experience shows that only the most motivated and diligent programmers will make that effort. We know that most programs would be improved if we could just get you to use the various whizzy features that we provide, but the defaults conspire against us. We have long wanted to do something to make it easier for our users to use the linkers more effectively. There have been many conversations over the years regarding this issue, and how to address it. They always break down along the following lines: Change ld Defaults Since the world would be a better place the newer ld features were the defaults, why not change things to make it so? This idea is simple, elegant, and impossible. Doing so would break a large number of existing applications, including those of ISVs, big customers, and a plethora of existing open source packages. In each case, the owner of that code may choose to follow our lead and fix their code, or they may view it as an invitation to reconsider their commitment to our platform. Backward compatibility, and our installed base of working software, is one of our greatest assets, and not something to be lightly put at risk. Breaking backward compatibility at this level of the system is likely to do more harm than good. But, it sure is tempting. New Link-Editor One might create a new linker command, not called 'ld', leaving the old command as it is. The new one could use the same code as ld, but would offer only modern options, with the proper defaults for features such as direct binding. The resulting link-editor would be a pleasure to use. However, the approach is doomed to niche status. There is a vast pile of exiting code in the world built around the existing ld command, that reaches back to the 1970's. ld use is embedded in large and unknown numbers of makefiles, and is used by name by compilers that execute it. A Unix link-editor that is not named ld will not find a majority audience no matter how good it might be. Finally, a new linker command will eventually cease to be new, and will accumulate its own burden of backward compatibility issues. An Option To Make ld Do The Right Things Automatically This line of reasoning is best summarized by a CR filed in 2005, entitled 6239804 make it easier for ld(1) to do what's best The idea is to have a '-z best' option that unchains ld from its backward compatibility commitment, and allows it to turn on the "best" set of features, as determined by the authors of ld. The specific set of features enabled by -z best would be subject to change over time, as requirements change. This idea is more realistic than the other two, but was never implemented because it has some important issues that we could never answer to our satisfaction: The -z best proposal assumes that the user can turn it on, and trust it to select good options without the user needing to be aware of the options being applied. This is a fallacy. Features such as direct bindings require the user to do some analysis to ensure that the resulting program will still operate properly. A user who is willing to do the work to verify that what -z best does will be OK for their application is capable of turning on those features directly, and therefore gains little added benefit from -z best. The intent is that when a user opts into -z best, that they understand that z best is subject to sometimes incompatible evolution. Experience teaches us that this won't work. People will use this feature, the meaning of -z best will change, code that used to build will fail, and then there will be complaints and demands to retract the change. When (not if) this occurs, we will of course defend our actions, and point at the disclaimer. We'll win some of those debates, and lose others. Ultimately, we'll end up with -z best2 (-z better), or other compromises, and our goal of simplifying the world will have failed. The -z best idea rolls up a set of features that may or may not be related to each other into a unit that must be taken wholesale, or not at all. It could be that only a subset of what it does is compatible with a given application, in which case the user is expected to abandon -z best and instead set the options that apply to their application directly. In doing so, they lose one of the benefits of -z best, that if you use it, future versions of ld may choose a different set of options, and automatically improve the object through the act of rebuilding it. I drew two conclusions from the above history: For a link-editor, backward compatibility is vital. If a given command line linked your application 10 years ago, you have every reason to expect that it will link today, assuming that the libraries you're linking against are still available and compatible with their previous interfaces. For an application of any size or complexity, there is no substitute for the work involved in examining the code and determining which linker options apply and which do not. These options are largely orthogonal to each other, and it can be reasonable not to use any or all of them, depending on the situation, even in modern applications. It is a mistake to tie them together. The idea for -z guidance came from consideration of these points. By decoupling the advice from the act of taking the advice, we can retain the good aspects of -z best while avoiding its pitfalls: -z guidance gives advice, but the decision to take that advice remains with the user who must evaluate its merit and make a decision to take it or not. As such, we are free to change the specific guidance given in future releases of ld, without breaking existing applications. The only fallout from this will be some new warnings in the build output, which can be ignored or dealt with at the user's convenience. It does not couple the various features given into a single "take it or leave it" option, meaning that there will never be a need to offer "-zguidance2", or other such variants as things change over time. Guidance has the potential to be our final word on this subject. The user is given the flexibility to disable specific categories of guidance without losing the benefit of others, including those that might be added to future versions of the system. Although -z fatal-warnings stands on its own as a useful feature, it is of particular interest in combination with -z guidance. Used together, the guidance turns from advice to hard requirement: The user must either make the suggested change, or explicitly reject the advice by specifying a guidance exception token, in order to get a build. This is valuable in environments with high coding standards. ld Command Line Options The guidance effort resulted in new link-editor options for guidance and for turning warnings into fatal errors. Before I reproduce that text here, I'd like to highlight the strategic decisions embedded in the guidance feature: In order to get guidance, you have to opt in. We hope you will opt in, and believe you'll get better objects if you do, but our default mode of operation will continue as it always has, with full backward compatibility, and without judgement. Guidance suggestions always offers specific advice, and not vague generalizations. You can disable some guidance without turning off the entire feature. When you get guidance warnings, you can choose to take the advice, or you can specify a keyword to disable guidance for just that category. This allows you to get guidance for things that are useful to you, without being bothered about things that you've already considered and dismissed. As the world changes, we will add new guidance to steer you in the right direction. All such new guidance will come with a keyword that let's you turn it off. In order to facilitate building your code on different versions of Solaris, we quietly ignore any guidance keywords we don't recognize, assuming that they are intended for newer versions of the link-editor. If you want to see what guidance tokens ld does and does not recognize on your system, you can use the ld debugging feature as follows: % ld -Dargs -z guidance=foo,nodefs debug: debug: Solaris Linkers: 5.11-1.2275 debug: debug: arg[1] option=-D: option-argument: args debug: arg[2] option=-z: option-argument: guidance=foo,nodefs debug: warning: unrecognized -z guidance item: foo The -z fatal-warning option is straightforward, and generally useful in environments with strict coding standards. Note that the GNU ld already had this feature, and we accept their option names as synonyms: -z fatal-warnings | nofatal-warnings --fatal-warnings | --no-fatal-warnings The -z fatal-warnings and the --fatal-warnings option cause the link-editor to treat warnings as fatal errors. The -z nofatal-warnings and the --no-fatal-warnings option cause the link-editor to treat warnings as non-fatal. This is the default behavior. The -z guidance option is defined as follows: -z guidance[=item1,item2,...] Provide guidance messages to suggest ld options that can improve the quality of the resulting object, or which are otherwise considered to be beneficial. The specific guidance offered is subject to change over time as the system evolves. Obsolete guidance offered by older versions of ld may be dropped in new versions. Similarly, new guidance may be added to new versions of ld. Guidance therefore always represents current best practices. It is possible to enable guidance, while preventing specific guidance messages, by providing a list of item tokens, representing the class of guidance to be suppressed. In this way, unwanted advice can be suppressed without losing the benefit of other guidance. Unrecognized item tokens are quietly ignored by ld, allowing a given ld command line to be executed on a variety of older or newer versions of Solaris. The guidance offered by the current version of ld, and the item tokens used to disable these messages, are as follows. Specify Required Dependencies Dynamic executables and shared objects should explicitly define all of the dependencies they require. Guidance recommends the use of the -z defs option, should any symbol references remain unsatisfied when building dynamic objects. This guidance can be disabled with -z guidance=nodefs. Do Not Specify Non-Required Dependencies Dynamic executables and shared objects should not define any dependencies that do not satisfy the symbol references made by the dynamic object. Guidance recommends that unused dependencies be removed. This guidance can be disabled with -z guidance=nounused. Lazy Loading Dependencies should be identified for lazy loading. Guidance recommends the use of the -z lazyload option should any dependency be processed before either a -z lazyload or -z nolazyload option is encountered. This guidance can be disabled with -z guidance=nolazyload. Direct Bindings Dependencies should be referenced with direct bindings. Guidance recommends the use of the -B direct, or -z direct options should any dependency be processed before either of these options, or the -z nodirect option is encountered. This guidance can be disabled with -z guidance=nodirect. Pure Text Segment Dynamic objects should not contain relocations to non-writable, allocable sections. Guidance recommends compiling objects with Position Independent Code (PIC) should any relocations against the text segment remain, and neither the -z textwarn or -z textoff options are encountered. This guidance can be disabled with -z guidance=notext. Mapfile Syntax All mapfiles should use the version 2 mapfile syntax. Guidance recommends the use of the version 2 syntax should any mapfiles be encountered that use the version 1 syntax. This guidance can be disabled with -z guidance=nomapfile. Library Search Path Inappropriate dependencies that are encountered by ld are quietly ignored. For example, a 32-bit dependency that is encountered when generating a 64-bit object is ignored. These dependencies can result from incorrect search path settings, such as supplying an incorrect -L option. Although benign, this dependency processing is wasteful, and might hide a build problem that should be solved. Guidance recommends the removal of any inappropriate dependencies. This guidance can be disabled with -z guidance=nolibpath. In addition, -z guidance=noall can be used to entirely disable the guidance feature. See Chapter 7, Link-Editor Quick Reference, in the Linker and Libraries Guide for more information on guidance and advice for building better objects. Example The following example demonstrates how the guidance feature is intended to work. We will build a shared object that has a variety of shortcomings: Does not specify all it's dependencies Specifies dependencies it does not use Does not use direct bindings Uses a version 1 mapfile Contains relocations to the readonly allocable text (not PIC) This scenario is sadly very common — many shared objects have one or more of these issues. % cat hello.c #include <stdio.h> #include <unistd.h> void hello(void) { printf("hello user %d\n", getpid()); } % cat mapfile.v1 # This version 1 mapfile will trigger a guidance message % cc hello.c -o hello.so -G -M mapfile.v1 -lelf As you can see, the operation completes without error, resulting in a usable object. However, turning on guidance reveals a number of things that could be better: % cc hello.c -o hello.so -G -M mapfile.v1 -lelf -zguidance ld: guidance: version 2 mapfile syntax recommended: mapfile.v1 ld: guidance: -z lazyload option recommended before first dependency ld: guidance: -B direct or -z direct option recommended before first dependency Undefined first referenced symbol in file getpid hello.o (symbol belongs to implicit dependency /lib/libc.so.1) printf hello.o (symbol belongs to implicit dependency /lib/libc.so.1) ld: warning: symbol referencing errors ld: guidance: -z defs option recommended for shared objects ld: guidance: removal of unused dependency recommended: libelf.so.1 warning: Text relocation remains referenced against symbol offset in file .rodata1 (section) 0xa hello.o getpid 0x4 hello.o printf 0xf hello.o ld: guidance: position independent (PIC) code recommended for shared objects ld: guidance: see ld(1) -z guidance for more information Given the explicit advice in the above guidance messages, it is relatively easy to modify the example to do the right things: % cat mapfile.v2 # This version 2 mapfile will not trigger a guidance message $mapfile_version 2 % cc hello.c -o hello.so -Kpic -G -Bdirect -M mapfile.v2 -lc -zguidance There are situations in which the guidance does not fit the object being built. For instance, you want to build an object without direct bindings: % cc -Kpic hello.c -o hello.so -G -M mapfile.v2 -lc -zguidance ld: guidance: -B direct or -z direct option recommended before first dependency ld: guidance: see ld(1) -z guidance for more information It is easy to disable that specific guidance warning without losing the overall benefit from allowing the remainder of the guidance feature to operate: % cc -Kpic hello.c -o hello.so -G -M mapfile.v2 -lc -zguidance=nodirect Conclusions The linking guidelines enforced by the ld guidance feature correspond rather directly to our standards for building the core Solaris OS. I'm sure that comes as no surprise. It only makes sense that we would want to build our own product as well as we know how. Solaris is usually the first significant test for any new linker feature. We now enable guidance by default for all builds, and the effect has been very positive. Guidance helps us find suboptimal objects more quickly. Programmers get concrete advice for what to change instead of vague generalities. Even in the cases where we override the guidance, the makefile rules to do so serve as documentation of the fact. Deciding to use guidance is likely to cause some up front work for most code, as it forces you to consider using new features such as direct bindings. Such investigation is worthwhile, but does not come for free. However, the guidance suggestions offer a structured and straightforward way to tackle modernizing your objects, and once that work is done, for keeping them that way. The investment is often worth it, and will replay you in terms of better performance and fewer problems. I hope that you find guidance to be as useful as we have.

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