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• Should a new language compiler target the JVM?

  - by Pindatjuh

  I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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• How To Compile YACC And LEX?

  - by nisha

  Actually I'm having YACC file as pos.yacc and LEX file name is pos1.lex.. while compilling I'm getting the folowing error... malathy@malathy:~$ cc lex.yy.c y.tab.c -ly -ll pos1.lex %{ #include "y.tab.h" int yylval; %} DIGIT [0-9]+ %% {DIGIT} {yylval=atoi(yytext);return DIGIT;} [\n ] {} . {return *yytext;} %% yacc file is pos.yacc %token DIGIT %% s:e {printf("%d\n",$1);} e:DIGIT {$$=$1;} |e e "+" {$$=$1+$2;} |e e "*" {$$=$1*$2;} |e e "-" {$$=$1-$2;} |e e "/" {$$=$1/$2;} ; %% main() { yyparse(); } yyerror() { printf("Error"); } so while compiling i m getting like malathy@malathy:~$ cc lex.yy.c y.tab.c -ly -ll pos.y: In function ‘yyerror’: pos.y:16: warning: incompatible implicit declaration of built-in function ‘printf’ pos.y: In function ‘yyparse’: pos.y:4: warning: incompatible implicit declaration of built-in function ‘printf’

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• When to use certain optimizations such as -fwhole-program and -fprofile-generate with several shared libraries

  - by James

  Probably a simple answer; I get quite confused with the language used in the GCC documentation for some of these flags! Anyway, I have three libraries and a programme which uses all these three. I compile each of my libraries seperately with individual (potentially) different sets of warning flags. However, I compile all three libraries with the same set of optimisation flags. I then compile my main programme linking in these three libraries with its own set of warning flags and the same optimisation flags used during the libraries' compilation. 1) Do I have to compile the libraries with optimisation flags present or can I just use these flags when compiling the final programme and linking to the libraries? If the latter, will it then optimise all or just some (presumably that which is called) of the code in these libraries? 2) I would like to use -fwhole-program -flto -fuse-linker-plugin and the linker plugin gold. At which stage do I compile with these on ... just the final compilation or do these flags need to be present during the compilation of the libraries? 3) Pretty much the same as 2) however with, -fprofile-generate -fprofile-arcs and -fprofile-use. I understand one first runs a programme with generate, and then with use. However, do I have to compile each of the libraries with generate/use etc. or just the final programme? And if it is just the last programme, when I then compeil with -fprofile-use will it also optimise the libraries functionality? Many thanks, James

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• iphone encode problem with ffmpeg

  - by samantha

  Hi, I need to encode a video from image. I use ffmpeg and compiling rigth. My problem is that when i try to opne video with quicktime on iphone, this give me a message "this movie format is not supported". I create a file mp4 with this parameter on context: context-time_base.num = 1; context-time_base.den = 15; context-codec_type = CODEC_TYPE_VIDEO; context-codec_id = CODEC_ID_H264; context-bit_rate = 1000000; context-width = width; context-height = height; context-keyint_min = 10; context-i_quant_factor = 0.71; context-bit_rate_tolerance = 20000; context-rc_max_rate = 100000; context-rc_buffer_size = 8835000; context-qcompress = 0.6; context-qmin = 10; context-qmax = 30; context-max_qdiff = 4; context-gop_size = 30; context->time_base.num = 1; context-time_base.den = 30; context-sample_aspect_ratio = av_d2q(1, 255); context-profile = 30; context-pix_fmt = PIX_FMT_YUV420P; context-flags |= CODEC_FLAG_LOOP_FILTER; where is my mistake?? thanks

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• A monkey could do this better - Access to and availability of private member functions in C++

  - by David

  I am wandering the desert of my brain. I'm trying to write something like the following: class MyClass { // Peripherally Related Stuff public: void TakeAnAction(int oneThing, int anotherThing) { switch(oneThing){ case THING_A: TakeThisActionWith(anotherThing); break; //cases THINGS_NOT_A: }; private: void TakeThisActionWith(int thing) { string outcome = new string; outcome = LookUpOutcome(thing); // Do some stuff based on outcome return; } string LookUpOutcome(int key) { string oc = new string; oc = MyPrivateMap[key]; return oc; } map<int, string> MyPrivateMap; Then in the .cc file where I am actually using these things, while compiling the TakeAnAction section, it [CC, the solaris compiler] throws an an error: 'The function LookUpOutcome must have a prototype' and bombs out. In my header file, I have declared 'string LookUpOutcome(int key);' in the private section of the class. I have tried all sorts of variations. I tried to use 'this' for a little while, and it gave me 'Can only use this in non-static member function.' Sadly, I haven't declared anything static and these are all, putatively, member functions. I tried it [on TakeAnAction and LookUp] when I got the error, but I got something like, 'Can't access MyPrivateMap from LookUp'. MyPrivateMap could be made public and I could refer to it directly, I guess, but my sensibility says that is not the right way to go about this [that means that namespace scoped helper functions are out, I think]. I also guess I could just inline the lookup and subsequent other stuff, but my line-o-meter goes on tilt. I'm trying desperately not to kludge it.

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• How to include external classes in a GAE deployment?

  - by kodra

  I am using the Google plug-in for Eclipse and have the following problem: The project consists of a GWT based GUI talking to a server running on GAE and using JPA. Additionally there is a project to migrate the legacy data to the new datastore. Since these both project use common data model, I have extracted a set of interfaces and enums into a separate project and set the other two projects dependencies on it. The Java App project seems to work, but the GWT/GAE only works if I manually copy the classes into the WEB-INF/classes directory. Obviously this is only working when using the housted mode. Anybody knows how to configure such a multi project setup in Eclipse? Also, I am not sure if the multi project layout is the best solution. The set of common model objects is used in all 3 areas: user client (GWT project compiling standard folders client and shared) server side (providing services for GWT-RPC, uploading and different feeds) migration application (posting the legacy data to the upload servlet) What are the architectural options to keep the amount of duplicated classes on minimum?

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• How to include all objects of an archive in a shared object?

  - by Didier Trosset

  When compiling our project, we create several archives (static libraries), say liby.a and libz.a that each contains an object file defining a function y_function() and z_function(). Then, these archives are joined in a shared object, say libyz.so, that is one of our main distributable target. g++ -fPIC -c -o y.o y.cpp ar cr liby.a y.o g++ -fPIC -c -o z.o z.cpp ar cr libz.a z.o g++ -shared -L. -ly -lz -o libyz.so When using this shared object into the example program, say x.c, the link fails because of an undefined references to functions y_function() and z_function(). g++ x.o -L. -lyz -o xyz It works however when I link the final executable directly with the archives (static libraries). g++ x.o -L. -ly -lz -o xyz My guess is that the object files contained in the archives are not linked into the shared library because they are not used in it. How to force inclusion? Edit: Inclusion can be forced using --whole-archive ld option. But if results in compilation errors: g++ -shared '-Wl,--whole-archive' -L. -ly -lz -o libyz.so /usr/lib/libc_nonshared.a(elf-init.oS): In function `__libc_csu_init': (.text+0x1d): undefined reference to `__init_array_end' /usr/bin/ld: /usr/lib/libc_nonshared.a(elf-init.oS): relocation R_X86_64_PC32 against undefined hidden symbol `__init_array_end' can not be used when making a shared object /usr/bin/ld: final link failed: Bad value Any idea where this comes from?

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• QT QSslError being signaled with the error code set to NoError

  - by Nantucket

  My Problem I compiled OpenSSL into QT to enable OpenSSL support. Everything appeared to go correctly in the compile. However, when I try to use the official HTTP example application that can be found here, everytime I try to download an https page, it will signal two QSslError, each with contents NoError. The types of QSslErrors, including NoError, are documented here, poorly. There is no explanation on why they even included an error type called NoError, or what it means. Bizarrely, the NoError error code seems to be true, as it downloads the remote https document perfectly even while signaling the error. Does anyone have any idea what this means and what could possibly be causing it? Optional Background Reading Here is the relevant part of the code from the example app (this is connected to the network connection's sslErrors signal by the constructor): void HttpWindow::sslErrors(QNetworkReply*,const QList<QSslError> &errors) { QString errorString; foreach (const QSslError &error, errors) { if (!errorString.isEmpty()) errorString += ", "; errorString += error.errorString(); } if (QMessageBox::warning(this, tr("HTTP"), tr("One or more SSL errors has occurred: %1").arg(errorString), QMessageBox::Ignore | QMessageBox::Abort) == QMessageBox::Ignore) { reply->ignoreSslErrors(); } } I have tried the old version of this example, and it produced the same result. I have tried OpenSSL 1.0.0a and 0.9.8o. I have tried tried compiling OpenSSL myself, I have tried using pre-compiled versions of OpenSSL from the net. All produce the same result. If this were my first time using QT with SSL, I would almost think this is the intended result (even though their example application is popping up error warning message windows), if not for the fact that last time I played with QT, using what would now be an old version of QT with an old version of SSL, I distinctly remember everything working fine with no error windows. My system is running Windows 7 x64.

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• Accessing Members of Containing Objects from Contained Objects.

  - by Bunkai.Satori

  If I have several levels of object containment (one object defines and instantiates another object which define and instantiate another object..), is it possible to get access to upper, containing - object variables and functions, please? Example: class CObjectOne { public: CObjectOne::CObjectOne() { Create(); }; void Create(); std::vector<ObjectTwo>vObejctsTwo; int nVariableOne; } bool CObjectOne::Create() { CObjectTwo ObjectTwo(this); vObjectsTwo.push_back(ObjectTwo); } class CObjectTwo { public: CObjectTwo::CObjectTwo(CObjectOne* pObject) { pObjectOne = pObject; Create(); }; void Create(); CObjectOne* GetObjectOne(){return pObjectOne;}; std::vector<CObjectTrhee>vObjectsTrhee; CObjectOne* pObjectOne; int nVariableTwo; } bool CObjectTwo::Create() { CObjectThree ObjectThree(this); vObjectsThree.push_back(ObjectThree); } class CObjectThree { public: CObjectThree::CObjectThree(CObjectTwo* pObject) { pObjectTwo = pObject; Create(); }; void Create(); CObjectTwo* GetObjectTwo(){return pObjectTwo;}; std::vector<CObjectsFour>vObjectsFour; CObjectTwo* pObjectTwo; int nVariableThree; } bool CObjectThree::Create() { CObjectFour ObjectFour(this); vObjectsFour.push_back(ObjectFour); } main() { CObjectOne myObject1; } Say, that from within CObjectThree I need to access nVariableOne in CObjectOne. I would like to do it as follows: int nValue = vObjectThree[index].GetObjectTwo()->GetObjectOne()->nVariable1; However, after compiling and running my application, I get Memory Access Violation error. What is wrong with the code above(it is example, and might contain spelling mistakes)? Do I have to create the objects dynamically instead of statically? Is there any other way how to achieve variables stored in containing objects from withing contained objects?

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• LINQ Join on Dictionary<K,T> where only K is changed.

  - by Stacey

  Assuming type TModel, TKey, and TValue. In a dictionary where KeyValuePair is declared, I need to merge TKey into a separate model of KeyValuePair where TKey in the original dictionary refers to an identifier in a list of TModel that will replace the item in the Dictionary. public TModel { public Guid Id { get; set; } // ... } public Dictionary<Guid, TValue> contains the elements. TValue relates to the TModel. The serialized/stored object is like this.. public SerializedModel { public Dictionary<Guid,TValue> Items { get; set; } } So I need to construct a new model... KeyValueModel { public Dictionary<TModel, TValue> { get; set; } } KeyValueModel kvm = = (from tModels in controller.ModelRepository.List<Models.Models>() join matchingModels in storedInformation.Items on tModels.Id equals matchingModels select tModels).ToDictionary( c => c.Id, storedInformation.Items.Values ) This linq query isn't doing what I'm wanting, but I think I'm at least headed in the right direction. Can anyone assist with the query? The original object is stored as a KeyValuePair. I need to merge the Guid Keys in the Dictionary to their actual related objects in another object (List) so that the final result is KeyValuePair. And as for what the query is not doing for me... it isn't compiling or running. It just says that "Join is not valid".

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• steps to fix a project that won't compile

  - by eco_bach

  Hi Pulling my hair out in trying to get a simple window based project to compile. I am running both 3.2.2 and 3.2.3 versions of Xcode. The latter is set up in a separate folder. Originally I used the latter to create and compile my project against the new 4.0 sdk. It compiled fine. Then I made the mistake of deleting some sdks I thought I no longer needed. Ever since I can no longer compile. Right now I get a dozen or so errors similar to the following "_OBJC_CLASS_$_CATransition", referenced from: objc-class-ref-to-CATransition in ViewTransitionsAppDelegate.o My active executable is the iphone simulator 4 and Base SDK is iPhone device 3.0. I tried reinstalling the xcode3.2.3 installer, no difference. I'm totally stymied, as my project WAS working and compiling fine, both to the simulator and external device. Are there any best practices or recommended steps in fixing or rebuilding a project when it won't compile? Any help welcome!

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• Help with Assembly/SSE Multiplication

  - by Brett

  I've been trying to figure out how to gain some improvement in my code at a very crucial couple lines: float x = a*b; float y = c*d; float z = e*f; float w = g*h; all a, b, c... are floats. I decided to look into using SSE, but can't seem to find any improvement, in fact it turns out to be twice as slow. My SSE code is: Vector4 abcd, efgh, result; abcd = [float a, float b, float c, float d]; efgh = [float e, float f, float g, float h]; _asm { movups xmm1, abcd movups xmm2, efgh mulps xmm1, xmm2 movups result, xmm1 } I also attempted using standard inline assembly, but it doesn't appear that I can pack the register with the four floating points like I can with SSE. Any comments, or help would be greatly appreciated, I mainly need to understand why my calculations using SSE are slower than the serial C++ code? I'm compiling in Visual Studio 2005, on a Windows XP, using a Pentium 4 with HT if that provides any additional information to assit. Thanks in advance!

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• VS 2008 C++ build output?

  - by STingRaySC

  Why when I watch the build output from a VC++ project in VS do I see: 1Compiling... 1a.cpp 1b.cpp 1c.cpp 1d.cpp 1e.cpp [etc...] 1Generating code... 1x.cpp 1y.cpp [etc...] The output looks as though several compilation units are being handled before any code is generated. Is this really going on? I'm trying to improve build times, and by using pre-compiled headers, I've gotten great speedups for each ".cpp" file, but there is a relatively long pause during the "Generating Code..." message. I do not have "Whole Program Optimization" nor "Link Time Code Generation" turned on. If this is the case, then why? Why doesn't VC++ compile each ".cpp" individually (which would include the code generation phase)? If this isn't just an illusion of the output, is there cross-compilation-unit optimization potentially going on here? There don't appear to be any compiler options to control that behavior (I know about WPO and LTCG, as mentioned above). EDIT: The build log just shows the ".obj" files in the output directory, one per line. There is no indication of "Compiling..." vs. "Generating code..." steps. EDIT: I have confirmed that this behavior has nothing to do with the "maximum number of parallel project builds" setting in Tools - Options - Projects and Solutions - Build and Run. Nor is it related to the MSBuild project build output verbosity setting. Indeed if I cancel the build before the "Generating code..." step, the ".obj" files will not exist for the most recent set of "compiled" files. E.g., if I cancel the build during "c.cpp" above, I will see only "a.obj" and "b.obj".

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• Why do bind1st and bind2nd require constant function objects?

  - by rlbond

  So, I was writing a C++ program which would allow me to take control of the entire world. I was all done writing the final translation unit, but I got an error: error C3848: expression having type 'const `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>' would lose some const-volatile qualifiers in order to call 'void `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>::operator ()(const point::Point &,const int &)' with [ T=SideCounter, BinaryFunction=std::plus<int> ] c:\program files (x86)\microsoft visual studio 9.0\vc\include\functional(324) : while compiling class template member function 'void std::binder2nd<_Fn2>::operator ()(point::Point &) const' with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] c:\users\****\documents\visual studio 2008\projects\TAKE_OVER_THE_WORLD\grid_divider.cpp(361) : see reference to class template instantiation 'std::binder2nd<_Fn2>' being compiled with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] I looked in the specifications of binder2nd and there it was: it took a const AdaptibleBinaryFunction. So, not a big deal, I thought. I just used boost::bind instead, right? Wrong! Now my take-over-the-world program takes too long to compile (bind is used inside a template which is instantiated quite a lot)! At this rate, my nemesis is going to take over the world first! I can't let that happen -- he uses Java! So can someone tell me why this design decision was made? It seems like an odd decision. I guess I'll have to make some of the elements of my class mutable for now...

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• How to read properties file in Greek using Java

  - by Subhendu Mahanta

  I am trying to read from a properties file which have keys in English & values in greek.My code is like this: public class I18NSample { static public void main(String[] args) { String language; String country; if (args.length != 2) { language = new String("el"); country = new String("GR"); } else { language = new String(args[0]); country = new String(args[1]); } Locale currentLocale; ResourceBundle messages; currentLocale = new Locale(language, country); messages = ResourceBundle.getBundle("MessagesBundle",currentLocale, new CustomClassLoader("E:\\properties")); System.out.println(messages.getString("greetings")); System.out.println(messages.getString("inquiry")); System.out.println(messages.getString("farewell")); } } import java.io.File; import java.net.MalformedURLException; import java.net.URL; public class CustomClassLoader extends ClassLoader { private String path; public CustomClassLoader(String path) { super(); this.path = path; } @Override protected URL findResource(String name) { File f = new File(path + File.separator + name); try { return f.toURL(); } catch (MalformedURLException e) { e.printStackTrace(); } return super.findResource(name); } } MessagesBundle_el_GR.properties greetings=??µ. ?a??et? farewell=ep?f. a?t?? inquiry=t? ???e?s, t? ???ete I am compiling like this javac -encoding UTF8 CustomClassLoader.java javac -encoding UTF8 I18Sample.java When I run this I get garbled output.If the properies file is in English,French or German it works fine. Please help. Regards, Subhendu

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• derived class as default argument g++

  - by Vincent

  Please take a look at this code: template<class T> class A { class base { }; class derived : public A<T>::base { }; public: int f(typename A<T>::base& arg = typename A<T>::derived()) { return 0; } }; int main() { A<int> a; a.f(); return 0; } Compiling generates the following error message in g++: test.cpp: In function 'int main()': test.cpp:25: error: default argument for parameter of type 'A<int>::base&' has type 'A<int>::derived' The basic idea (using derived class as default value for base-reference-type argument) works in visual studio, but not in g++. I have to publish my code to the university server where they compile it with gcc. What can I do? Is there something I am missing?

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• Indentation control while developing a small python like language

  - by sap

  Hello, I'm developing a small python like language using flex, byacc (for lexical and parsing) and C++, but i have a few questions regarding scope control. just as python it uses white spaces (or tabs) for indentation, not only that but i want to implement index breaking like for instance if you type "break 2" inside a while loop that's inside another while loop it would not only break from the last one but from the first loop as well (hence the number 2 after break) and so on. example: while 1 while 1 break 2 'hello world'!! #will never reach this. "!!" outputs with a newline end 'hello world again'!! #also will never reach this. again "!!" used for cout end #after break 2 it would jump right here but since I don't have an "anti" tab character to check when a scope ends (like C for example i would just use the '}' char) i was wondering if this method would the the best: I would define a global variable, like "int tabIndex" on my yacc file that i would access in my lex file using extern. then every time i find a tab character on my lex file i would increment that variable by 1. when parsing on my yacc file if i find a "break" keyword i would decrement by the amount typed after it from the tabIndex variable, and when i reach and EOF after compiling and i get a tabIndex != 0 i would output compilation error. now the problem is, whats the best way to see if the indentation got reduced, should i read \b (backspace) chars from lex and then reduce the tabIndex variable (when the user doesn't use break)? another method to achieve this? also just another small question, i want every executable to have its starting point on the function called start() should i hardcode this onto my yacc file? sorry for the long question any help is greatly appreciated. also if someone can provide an yacc file for python would be nice as a guideline (tried looking on Google and had no luck). thanks in advance.

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• What are simple instructions for creating a Python package structure and egg?

  - by froadie

  I just completed my first (minor) Python project, and my boss wants me to package it nicely so that it can be distributed and called from other programs easily. He suggested I look into eggs. I've been googling and reading, but I'm just getting confused. Most of the sites I'm looking at explain how to use Python eggs that were already created, or how to create an egg from a setup.py file (which I don't yet have). All I have now is an Eclipse pydev project with about 4 modules and a settings/configuration file. In easy steps, how do I go about structuring it into folders/packages and compiling it into an egg? And once it's an egg, what do I have to know about deploying/building/using it? I'm really starting from scratch here, so don't assume I know anything; simple step-by-step instructions would be really helpful... These are some of the sites that I've been looking at so far: http://peak.telecommunity.com/DevCenter/PythonEggs http://www.packtpub.com/article/writing-a-package-in-python http://www.ibm.com/developerworks/library/l-cppeak3.html#N10232 I've also browsed a few SO questions but haven't really found what I need. Thanks!

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• Cheap cloning/local branching in Mercurial

  - by Zack

  Hi, Just started working with Mercurial a few days ago and there's something I don't understand. I have an experimental thing I want to do, so the normal thing to do would be to clone my repository, work on the clone and if eventually I want to keep those changes, I'll push them to my main repository. Problem is cloning my repository takes alot of time (we have alot of code) and just compiling the cloned copy would take up to an hour. So I need to somehow work on a different repository but still in my original working copy. Enter local branches. Problem is just creating a local branch takes forever, and working with them isn't all that fun either. Because when moving between local branches doesn't "revert" to the target branch state, I have to issue a hg purge (to remove files that were added in the moved from branch) and then hg update -c (to revert modified files in the moved from branch). (note: I did try PK11 fork of local branch extension, it a simple local branch creation crashes with an exception) At the end of the day, this is just too complex. What are my options?

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• Optimal Eclipse CDT (C++) experience in March of 2010

  - by ahoffer

  I am a student who will be using C++ next quarter. I really enjoyed using the Galileo release of Eclipse with Java and I would like to continue using Eclipse for for C++ development. I am now experimenting with C++ development on Eclipse. I am running Eclipse 3.5 SR2 with CDT 6.02. My operating system is Windows 7 and I have installed MinGW-5.1.6. Version 6.3 of GDB is installed. I have it compiling and stepping through code. However, I have the suspicion that I'm just crawling along and have yet to "shift the car out of first gear". I've spent about a week poking around on the Web to learn what constitutes and "optimal" C++ Eclipse experience. In particular, I'm interested in round-tripping with UML and unit testing. My exploration of the Web became an archeological dig. I turned up how-to articles from 2003, alternative MinGW distros, references to plugins, dead-links, more references to plugins, passionate discussions on gdb bugs, and more references to plugins. I no longer have any idea what might constitute an optimal C++ Eclipse environment. Would members of the community like to weigh-in on what they consider to be the current optimal experience for C++ development using Eclipse?

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• Private member vector of vector dynamic memory allocation

  - by Geoffroy

  Hello, I'm new to C++ (I learned programming with Fortran), and I would like to allocate dynamically the memory for a multidimensional table. This table is a private member variable : class theclass{ public: void setdim(void); private: std::vector < std::vector <int> > thetable; } I would like to set the dimension of thetable with the function setdim(). void theclass::setdim(void){ this->thetable.assign(1000,std::vector <int> (2000)); } I have no problem compiling this program, but as I execute it, I've got a segmentation fault. The strange thing for me is that this piece (see under) of code does exactly what I want, except that it doesn't uses the private member variable of my class : std::vector < std::vector < int > > thetable; thetable.assign(1000,std::vector <int> (2000)); By the way, I have no trouble if thetable is a 1D vector. In theclass : std::vector < int > thetable; and if in setdim : this->thetable.assign(1000,2); So my question is : why is there such a difference with "assign" between thetable and this-thetable for a 2D vector? And how should I do to do what I want? Thank-you for your help, Best regards, -- Geoffroy

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• std::string insert method has ambiguous overloads?

  - by sdg

  Environment: VS2005 C++ using STLPort 5.1.4. Compiling the following code snippet: std::string copied = "asdf"; char ch = 's'; copied.insert(0,1,ch); I receive an error: Error 1 error C2668: 'stlpx_std::basic_string<_CharT,_Traits,_Alloc>::insert' : ambiguous call to overloaded function It appears that the problem is the insert method call on the string object. The two defined overloads are void insert ( iterator p, size_t n, char c ); string& insert ( size_t pos1, size_t n, char c ); But given that STLPort uses a simple char* as its iterator, the literal zero in the insert method in my code is ambiguous. So while I can easily overcome the problem by hinting such as copied.insert(size_t(0),1,ch); My question is: is this overloading and possible ambiguity intentional in the specification? Or more likely an unintended side-effect of the specific STLPort implementation? (Note that the Microsoft-supplied STL does not have this problem as it has a class for the iterator, instead of a naked pointer)

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• MSBuild / PowerShell: Copy SQL Server 2012 database to SQL Azure via BACPAC (for Continuous Integration)

  - by giveme5minutes

  I'm creating a continuous integration MSBuild script which copies a database in on-premise SQL Server 2012 to SQL Azure. Easy right? Methods After a fair bit of research I've come across the following methods: Use PowerShell to access the DAC library directly, then use the MSBuild PowerShell extension to wrap the script. This would require installing PowerShell 3 and working out how to make the MSBuild PowerShell extension work with it, as apparently MS moved the DAC API to a different namespace in the latest version of the library. PowerShell would give direct access to the API, but may require quite a bit of boilerplate. Use the sample DAC Framework Client Side Tools, which requires compiling them myself, as the downloads available from Codeplex only include the Hosted version. It would also require fixing them to use DAC 3.0 classes as they appear to currently use an earlier version of DAC. I could then call these tools from an <Exec Command="" /> in the MSBuild script. Less boilerplate and if I hit any bumps in the road I can just make changes to the source. Processes Using whichever method, the process could be either: Export from on-premise SQL Server 2012 to local BACPAC Upload BACPAC to blog storage Import BACPAC to SQL Azure via Hosted DAC Or: Export from on-premise SQL Server 2012 to local BACPAC Import BACPAC to SQL Azure via Client DAC Question All of the above seems to be quite a lot of effort for something that seems to be a standard feature... so before I start reinventing the wheel and documenting the results for all to see, is there something really obvious that I've missed here? Is there pre-written script that MS has released that I have not yet uncovered? There's an command in the GUI of SQL Server Management Studio 2012 that does EXACTLY what I'm trying to do (right click on local database, click "Tasks", click "Deploy Database to SQL Azure"). Surely if it's a few clicks in the GUI it must be a single command on the command line somewhere??

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• Newbie question: When to use extern "C" { //code } ?

  - by Russel

  Hello, Maybe I'm not understanding the differences between C and C++, but when and why do we need to use: extern "C" { ? Apparently its a "linkage convention"? I read about it briefly and noticed that all the .h header files included with MSVS surround their code with it. What type of code exactly is "C code" and NOT "C++ code"? I thought C++ included all C code? I'm guessing that this is not the case and that C++ is different and that standard features/functions exist in one or the other but not both (ie: printf is C and cout is C++), but that C++ is backwards compatible though the extern "C" declaration. Is this correct? My next question depends on the answer to the first, but I'll ask it here anyway: Since MSVS header files that are written in C are surrounded by extern "C" { ... }, when would you ever need to use this yourself in your own code? If your code is C code and you are trying to compile it in a C++ compiler, shouldn't it work without problem because all the standard h files you include will already have the extern "C" thing in them with the C++ compiler? Do you have to use this when compiling in C++ but linking to alteady built C libraries or something? Please help clarify this for me... Thanks! --Keith

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• Script to install and compile Python, Django, Virtualenv, Mercurial, Git, LessCSS, etc... on Dreamho

  - by tmslnz

  The Story After cleaning up my Dreamhost shared server's home folder from all the cruft accumulated over time, I decided to start afresh and compile/reinstall Python. All tutorials and snippets I found seemed overly simplistic, assuming (or ignoring) a bunch of dependencies needed by Python to compile all modules correctly. So, starting from http://andrew.io/weblog/2010/02/installing-python-2-6-virtualenv-and-virtualenvwrapper-on-dreamhost/ (so far the best guide I found), I decided to write a set-and-forget Bash script to automate this painful process, including along the way a bunch of other things I am planning to use. The Script I am hosting the script on http://bitbucket.org/tmslnz/python-dreamhost-batch/src/ The TODOs So far it runs fine, and does all it needs to do in about 900 seconds, giving me at the end of the process a fully functional Python / Mercurial / etc... setup without even needing to log out and back in. I though this might be of use for others too, but there are a few things that I think it's missing and I am not quite sure how to go for it, what's the best way to do it, or if this just doesn't make any sense at all. Check for errors and break Check for minor version bumps of the packages and give warnings Check for known dependencies Use arguments to install only some of the packages instead of commenting out lines Organise the code in a manner that's easy to update Optionally make the installers and compiling silent, with error logging to file failproof .bashrc modification to prevent breaking ssh logins and having to log back via FTP to fix it EDIT: The implied question is: can anyone, more bashful than me, offer general advice on the worthiness of the above points or highlight any problems they see with this approach? (see my answer to Ry4an's comment below) The Gist I am no UNIX or Bash or compiler expert, and this has been built iteratively, by trial and error. It is somehow going towards apt-get (well, 1% of it...), but since Dreamhost and others obviously cannot give root access on shared servers, this looks to me like a potentially very useful workaround; particularly so with some community work involved.

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