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• C++/msvc6 application crashes due to heap corruption, any hints?

  - by David Alfonso

  Hello all, let me say first that I'm writing this question after months of trying to find out the root of a crash happening in our application. I'll try to detail as much as possible what I've already found out about it. About the application It runs on Windows XP Professional SP2. It's built with Microsoft Visual C++ 6.0 with Service Pack 6. It's MFC based. It uses several external dlls (e.g. Xerces, ZLib or ACE). It has high performance requirements. It does a lot of network and hard disk I/O, but it's also cpu intensive. It has an exception handling mechanism which generates a minidump when an unhandled exception occurs. Facts about the crash It only happens on multiprocessor/multicore machines and under heavy loads of work. It happens at random (neither we nor our client have found a pattern yet). We cannot reproduce the crash on our testing lab. It only happens on some production systems (but always in multicore machines) It always ends up crashing at the same point, although the complete stack is not always the same. Let me add the stack of the crashing thread (obtained using WinDbg, sorry we don't have symbols) ChildEBP RetAddr Args to Child WARNING: Stack unwind information not available. Following frames may be wrong. 030af6c8 7c9206eb 77bfc3c9 01a80000 00224bc3 MyApplication+0x2a85b9 030af960 7c91e9c0 7c92901b 00000ab4 00000000 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030af98c 7c9205c8 00000001 00000000 00000000 ntdll!ZwWaitForSingleObject+0xc (FPO: [3,0,0]) 030af9c0 7c920551 01a80898 7c92056d 313adfb0 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030afa8c 4ba3ae96 000307da 00130005 00040012 ntdll!RtlFreeHeap+0x1e9 (FPO: [Non-Fpo]) 030afacc 77bfc2e3 0214e384 3087c8d8 02151030 0x4ba3ae96 030afb00 7c91e306 7c80bfc1 00000948 00000001 msvcrt!free+0xc8 (FPO: [Non-Fpo]) 030afb20 0042965b 030afcc0 0214d780 02151218 ntdll!ZwReleaseSemaphore+0xc (FPO: [3,0,0]) 030afb7c 7c9206eb 02e6c471 02ea0000 00000008 MyApplication+0x2965b 030afe60 7c9205c8 02151248 030aff38 7c920551 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030afe74 7c92056d 0210bfb8 02151250 02151250 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030aff38 77bfc2de 01a80000 00000000 77bfc2e3 ntdll!RtlFreeHeap+0x647 (FPO: [Non-Fpo]) 7c92056d c5ffffff ce7c94be ff7c94be 00ffffff msvcrt!free+0xc3 (FPO: [Non-Fpo]) 7c920575 ff7c94be 00ffffff 12000000 907c94be 0xc5ffffff 7c920579 00ffffff 12000000 907c94be 90909090 0xff7c94be *** WARNING: Unable to verify checksum for xerces-c_2_7.dll *** ERROR: Symbol file could not be found. Defaulted to export symbols for xerces-c_2_7.dll - 7c92057d 12000000 907c94be 90909090 8b55ff8b MyApplication+0xbfffff 7c920581 907c94be 90909090 8b55ff8b 08458bec xerces_c_2_7 7c920585 90909090 8b55ff8b 08458bec 04408b66 0x907c94be 7c920589 8b55ff8b 08458bec 04408b66 0004c25d 0x90909090 7c92058d 08458bec 04408b66 0004c25d 90909090 0x8b55ff8b The address MyApplication+0x2a85b9 corresponds to a call to erase() of a std::list. What I have tried so far Reviewing all the code related to the point where the crash ends happening. Trying to enable pageheap on our testing lab though nothing useful has been found by now. We have substituted the std::list for a C array and then it crashes in other part of the code (although it is related code, it's not in the code where the old list resided). Coincidentally, now it crashes in another erase, though this time of a std::multiset. Let me copy the stack contained in the dump: ntdll.dll!_RtlpCoalesceFreeBlocks@16() + 0x124e bytes ntdll.dll!_RtlFreeHeap@12() + 0x91f bytes msvcrt.dll!_free() + 0xc3 bytes MyApplication.exe!006a4fda() [Frames below may be incorrect and/or missing, no symbols loaded for MyApplication.exe] MyApplication.exe!0069f305() ntdll.dll!_NtFreeVirtualMemory@16() + 0xc bytes ntdll.dll!_RtlpSecMemFreeVirtualMemory@16() + 0x1b bytes ntdll.dll!_ZwWaitForSingleObject@12() + 0xc bytes ntdll.dll!_RtlpFreeToHeapLookaside@8() + 0x26 bytes ntdll.dll!_RtlFreeHeap@12() + 0x114 bytes msvcrt.dll!_free() + 0xc3 bytes c5ffffff() Possible solutions (that I'm aware of) which cannot be applied "Migrate the application to a newer compiler": We are working on this but It's not a solution at the moment. "Enable pageheap (normal or full)": We can't enable pageheap on production machines as this affects performance heavily. I think that's all I remember now, if I have forgotten something I'll add it asap. If you can give me some hint or propose some possible solution, don't hesitate to answer! Thank you in advance for your time and advice.

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• Can't update scala on Gentoo

  - by xhochy

  As I wanted to test Scala 2.9.2 on my gentoo system I tried updated the package but ended up with this error. I can't figure out where the problem may be: Calculating dependencies ...... done! >>> Verifying ebuild manifests >>> Jobs: 0 of 1 complete, 1 running Load avg: 0.23, 0.16, 0.20 >>> Emerging (1 of 1) dev-lang/scala-2.9.2 >>> Jobs: 0 of 1 complete, 1 running Load avg: 0.23, 0.16, 0.20 >>> Failed to emerge dev-lang/scala-2.9.2, Log file: >>> Jobs: 0 of 1 complete, 1 running Load avg: 0.23, 0.16, 0.20 >>> '/var/tmp/portage/dev-lang/scala-2.9.2/temp/build.log' >>> Jobs: 0 of 1 complete, 1 running Load avg: 0.23, 0.16, 0.20 >>> Jobs: 0 of 1 complete, 1 running, 1 failed Load avg: 0.23, 0.16, 0.20 >>> Jobs: 0 of 1 complete, 1 failed Load avg: 0.23, 0.16, 0.20 * Package: dev-lang/scala-2.9.2 * Repository: gentoo * Maintainer: [email protected] * USE: amd64 elibc_glibc kernel_linux multilib userland_GNU * FEATURES: sandbox [01m[31;06m!!! ERROR: Couldn't find suitable VM. Possible invalid dependency string. Due to jdk-with-com-sun requiring a target of 1.7 but the virtual machines constrained by virtual/jdk-1.6 and/or this package requiring virtual(s) jdk-with-com-sun[0m * Unable to determine VM for building from dependencies: NV_DEPEND: virtual/jdk:1.6 java-virtuals/jdk-with-com-sun !binary? ( dev-java/ant-contrib:0 ) app-arch/xz-utils >=dev-java/java-config-2.1.9-r1 source? ( app-arch/zip ) >=dev-java/ant-core-1.7.0 dev-java/ant-nodeps >=dev-java/javatoolkit-0.3.0-r2 >=dev-lang/python-2.4 * ERROR: dev-lang/scala-2.9.2 failed (setup phase): * Failed to determine VM for building. * * Call stack: * ebuild.sh, line 93: Called pkg_setup * scala-2.9.2.ebuild, line 43: Called java-pkg-2_pkg_setup * java-pkg-2.eclass, line 53: Called java-pkg_init * java-utils-2.eclass, line 2187: Called java-pkg_switch-vm * java-utils-2.eclass, line 2674: Called die * The specific snippet of code: * die "Failed to determine VM for building." * * If you need support, post the output of `emerge --info '=dev-lang/scala-2.9.2'`, * the complete build log and the output of `emerge -pqv '=dev-lang/scala-2.9.2'`. !!! When you file a bug report, please include the following information: GENTOO_VM= CLASSPATH="" JAVA_HOME="" JAVACFLAGS="" COMPILER="" and of course, the output of emerge --info * The complete build log is located at '/var/tmp/portage/dev-lang/scala-2.9.2/temp/build.log'. * The ebuild environment file is located at '/var/tmp/portage/dev-lang/scala-2.9.2/temp/die.env'. * Working directory: '/var/tmp/portage/dev-lang/scala-2.9.2' * S: '/var/tmp/portage/dev-lang/scala-2.9.2/work/scala-2.9.2-sources' * Messages for package dev-lang/scala-2.9.2: * Unable to determine VM for building from dependencies: * ERROR: dev-lang/scala-2.9.2 failed (setup phase): * Failed to determine VM for building. * * Call stack: * ebuild.sh, line 93: Called pkg_setup * scala-2.9.2.ebuild, line 43: Called java-pkg-2_pkg_setup * java-pkg-2.eclass, line 53: Called java-pkg_init * java-utils-2.eclass, line 2187: Called java-pkg_switch-vm * java-utils-2.eclass, line 2674: Called die * The specific snippet of code: * die "Failed to determine VM for building." * * If you need support, post the output of `emerge --info '=dev-lang/scala-2.9.2'`, * the complete build log and the output of `emerge -pqv '=dev-lang/scala-2.9.2'`. * The complete build log is located at '/var/tmp/portage/dev-lang/scala-2.9.2/temp/build.log'. * The ebuild environment file is located at '/var/tmp/portage/dev-lang/scala-2.9.2/temp/die.env'. * Working directory: '/var/tmp/portage/dev-lang/scala-2.9.2' * S: '/var/tmp/portage/dev-lang/scala-2.9.2/work/scala-2.9.2-sources' The following eix output may help: % eix java-virtuals/jdk-with-com-sun [I] java-virtuals/jdk-with-com-sun Available versions: 20111111 {{ELIBC="FreeBSD"}} Installed versions: 20111111(16:08:51 18/04/12)(ELIBC="-FreeBSD") Homepage: http://www.gentoo.org Description: Virtual ebuilds that require internal com.sun classes from a JDK Both virtual jdks 1.6 and 1.7 are installed: % eix virtual/jdk [I] virtual/jdk Available versions: (1.4) ~1.4.2-r1[1] (1.5) 1.5.0 ~1.5.0-r3[1] (1.6) 1.6.0 1.6.0-r1 (1.7) (~)1.7.0 Installed versions: 1.6.0-r1(1.6)(23:22:48 10/11/12) 1.7.0(1.7)(23:21:09 10/11/12) Description: Virtual for JDK [1] "java-overlay" /var/lib/layman/java-overlay

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• Resolve naming conflict in included XSDs for JAXB compilation

  - by Jason Faust

  I am currently trying to compile with JAXB (IBM build 2.1.3) a pair of schema files into the same package. Each will compile on it's own, but when trying to compile them together i get a element naming conflict due to includes. My question is; is there a way to specify with an external binding a resolution to the naming collision. Example files follow. In the example the offending element is called "Common", which is defined in both incA and incB: incA.xsd <?xml version="1.0" encoding="UTF-8"?> <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/" xmlns:tns="http://www.example.org/" elementFormDefault="qualified"> <complexType name="TypeA"> <sequence> <element name="ElementA" type="string"></element> </sequence> </complexType> <!-- Conflicting element --> <element name="Common" type="tns:TypeA"></element> </schema> incB.xsd <?xml version="1.0" encoding="UTF-8"?> <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/" xmlns:tns="http://www.example.org/" elementFormDefault="qualified"> <complexType name="TypeB"> <sequence> <element name="ElementB" type="int"></element> </sequence> </complexType> <!-- Conflicting element --> <element name="Common" type="tns:TypeB"></element> </schema> A.xsd <?xml version="1.0" encoding="UTF-8"?> <schema targetNamespace="http://www.example.org/" elementFormDefault="qualified" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.example.org/"> <include schemaLocation="incA.xsd"></include> <complexType name="A"> <sequence> <element ref="tns:Common"></element> </sequence> </complexType> </schema> B.xsd <?xml version="1.0" encoding="UTF-8"?> <schema targetNamespace="http://www.example.org/" elementFormDefault="qualified" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.example.org/"> <include schemaLocation="incB.xsd"></include> <complexType name="B"> <sequence> <element ref="tns:Common"></element> </sequence> </complexType> </schema> Compiler error when both are compiled from one evocation of xjb: [ERROR] 'Common' is already defined line 9 of file:/C:/temp/incB.xsd [ERROR] (related to above error) the first definition appears here line 9 of file:/C:/temp/incA.xsd (For reference, this is a generalization to resolve an issue with compiling the OAGIS8 SP3 package)

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• Why is the this-pointer needed to access inherited attributes?

  - by Shadow

  Hi, assume the following class is given: class Base{ public: Base() {} Base( const Base& b) : base_attr(b.base_attr) {} void someBaseFunction() { .... } protected: SomeType base_attr; }; When I want a class to inherit from this one and include a new attribute for the derived class, I would write: class Derived: public Base { public: Derived() {} Derived( const Derived& d ) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void SomeDerivedFunction() { .... } private: SomeOtherType derived_attr; }; This works for me (let's ignore eventually missing semicolons or such please). However, when I remove the "this-" in the copy constructor of the derived class, the compiler complains that "'base_attr' was not declared in this scope". I thought that, when inheriting from a class, the protected attributes would then also be accessible directly. I did not know that the "this-" pointer was needed. I am now confused if it is actually correct what I am doing there, especially the copy-constructor of the Derived-class. Because each Derived object is supposed to have a base_attr and a derived_attr and they obviously need to be initialized/set correctly. And because Derived is inheriting from Base, I don't want to explicitly include an attribute named "base_attr" in the Derived-class. IMHO doing so would generally destroy the idea behind inheritance, as everything would have to be defined again. EDIT Thank you all for the quick answers. I completely forgot the fact that the classes actually are templates. Please, see the new examples below, which are actually compiling when including "this-" and are failing when omiting "this-" in the copy-constructor of the Derived-class: Base-class: #include <iostream> template<class T> class Base{ public: Base() : base_attr(0) {} Base( const Base& b) : base_attr(b.base_attr) {} void baseIncrement() { ++base_attr; } void printAttr() { std::cout << "Base Attribute: " << base_attr << std::endl; } protected: T base_attr; }; Derived-class: #include "base.hpp" template< class T > class Derived: public Base<T>{ public: Derived() : derived_attr(1) {} Derived( const Derived& d) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void derivedIncrement() { ++derived_attr; } protected: T derived_attr; }; and for completeness also the main function: #include "derived.hpp" int main() { Derived<int> d; d.printAttr(); d.baseIncrement(); d.printAttr(); Derived<int> d2(d); d2.printAttr(); return 0; }; I am using g++-4.3.4. Although I understood now that it seems to come from the fact that I use template-class definitions, I did not quite understand what is causing the problem when using templates and why it works when not using templates. Could someone please further clarify this?

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• Simple Constructor With Initializer List? - C++

  - by Alex

  Hi all, below I've included my h file, and my problem is that the compiler is not liking my simple exception class's constructor's with initializer lists. It also is saying that string is undeclared identifier, even though I have #include <string> at the top of the h file. Do you see something I am doing wrong? For further explanation, this is one of my domain classes that I'm integrating into a wxWidgets GUI application on Windows. Thanks! Time.h #pragma once #include <string> #include <iostream> // global constants for use in calculation const int HOURS_TO_MINUTES = 60; const int MINUTES_TO_HOURS = 100; class Time { public: // default Time class constructor // initializes all vars to default values Time(void); // ComputeEndTime computes the new delivery end time // params - none // preconditions - vars will be error-free // postconditions - the correct end time will be returned as an int // returns an int int ComputeEndTime(); // GetStartTime is the getter for var startTime // params - none // returns an int int GetStartTime() { return startTime; } // GetEndTime is the getter for var endTime // params - none // returns an int int GetEndTime() { return endTime; } // GetTimeDiff is the getter for var timeDifference // params - none // returns a double double GetTimeDiff() { return timeDifference; } // SetStartTime is the setter for var startTime // params - an int // returns void void SetStartTime(int s) { startTime = s; } // SetEndTime is the setter for var endTime // params - an int // returns void void SetEndTime(int e) { endTime = e; } // SetTimeDiff is the setter for var timeDifference // params - a double // returns void void SetTimeDiff(double t) { timeDifference = t; } // destructor for Time class ~Time(void); private: int startTime; int endTime; double timeDifference; }; class HourOutOfRangeException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type HourOutOfRangeException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~HourOutOfRangeException() {} private: string message; }; class MinuteOutOfRangeException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type MinuteOutOfRangeException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~MinuteOutOfRangeException() {} private: string message; }; class PercentageOutOfRangeException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type PercentageOutOfRangeException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~PercentageOutOfRangeException() {} private: string message; }; class StartEndException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type StartEndException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~StartEndException() {} private: string message; };

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• Why is processing a sorted array faster than an unsorted array?

  - by GManNickG

  Here is a piece of code that shows some very peculiar performance. For some strange reason, sorting the data miraculously speeds up the code by almost 6x: #include <algorithm> #include <ctime> #include <iostream> int main() { // generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = 0; c < arraySize; ++c) data[c] = std::rand() % 256; // !!! with this, the next loop runs faster std::sort(data, data + arraySize); // test clock_t start = clock(); long long sum = 0; for (unsigned i = 0; i < 100000; ++i) { // primary loop for (unsigned c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC; std::cout << elapsedTime << std::endl; std::cout << "sum = " << sum << std::endl; } Without std::sort(data, data + arraySize);, the code runs in 11.54 seconds. With the sorted data, the code runs in 1.93 seconds. Initially I thought this might be just a language or compiler anomaly. So I tried it Java... import java.util.Arrays; import java.util.Random; public class Main { public static void main(String[] args) { // generate data int arraySize = 32768; int data[] = new int[arraySize]; Random rnd = new Random(0); for (int c = 0; c < arraySize; ++c) data[c] = rnd.nextInt() % 256; // !!! with this, the next loop runs faster Arrays.sort(data); // test long start = System.nanoTime(); long sum = 0; for (int i = 0; i < 100000; ++i) { // primary loop for (int c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } System.out.println((System.nanoTime() - start) / 1000000000.0); System.out.println("sum = " + sum); } } with a similar but less extreme result. My first thought was that sorting brings the data into cache, but my next thought was how silly that is because the array was just generated. What is going on? Why is a sorted array faster than an unsorted array? The code is summing up some independent terms, the order should not matter.

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• Invoke a SOAP method with namespace prefixes

  - by mvladic

  My C# web service client sends following soap message to Java-based web service: <?xml version="1.0" encoding="utf-8"?> <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <soap:Body> <getData> <request> <requestParameters xmlns="http://b..."> <equals> ... </equals> </requestParameters> </request> </getData> </soap:Body> </soap:Envelope> and Java-based web service returns error: 500 Internal Server Error ... Cannot find dispatch method for {}getData ... Client written in Java, which works, sends the following message: <?xml version="1.0" encoding="utf-8"?> <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <soap:Body> <ns2:getData xmlns:ns2="http://a..."> <ns2:request> <ns3:requestParameters xmlns:ns3="http://b..."> <ns3:equals> ... </ns3:equals> </ns3:requestParameters> </ns2:request> </ns2:getData> </soap:Body> </soap:Envelope> Is there an easy way in C# to send SOAP messages the same way Java client sends: with namespace prefixes? Following is C# code that sends message: // class MyService is auto-generated using wsdl.exe tool MyService service = new MyService(); RequestMessage request = new RequestMessage(); ... ResponseMessage response = service.getData(request); ... UPDATE: RequestMessage class looks like this: /// <remarks/> [System.CodeDom.Compiler.GeneratedCodeAttribute("svcutil", "3.0.4506.2152")] [System.SerializableAttribute()] [System.Diagnostics.DebuggerStepThroughAttribute()] [System.ComponentModel.DesignerCategoryAttribute("code")] [System.Xml.Serialization.XmlTypeAttribute(Namespace="http://uri.etsi.org/02657/v1.5.1#/RetainedData")] public partial class RequestMessage { private byte[] requestPriorityField; private RequestConstraints requestParametersField; private string deliveryPointHIBField; private string maxHitsField; private NationalRequestParameters nationalRequestParametersField; private System.Xml.XmlElement anyField; /// <remarks/> [System.Xml.Serialization.XmlElementAttribute(DataType="hexBinary", Order=0)] public byte[] requestPriority { get { return this.requestPriorityField; } set { this.requestPriorityField = value; } } /// <remarks/> [System.Xml.Serialization.XmlElementAttribute(Order=1)] public RequestConstraints requestParameters { get { return this.requestParametersField; } set { this.requestParametersField = value; } } /// <remarks/> [System.Xml.Serialization.XmlElementAttribute(Order=2)] public string deliveryPointHIB { get { return this.deliveryPointHIBField; } set { this.deliveryPointHIBField = value; } } /// <remarks/> [System.Xml.Serialization.XmlElementAttribute(DataType="integer", Order=3)] public string maxHits { get { return this.maxHitsField; } set { this.maxHitsField = value; } } /// <remarks/> [System.Xml.Serialization.XmlElementAttribute(Order=4)] public NationalRequestParameters nationalRequestParameters { get { return this.nationalRequestParametersField; } set { this.nationalRequestParametersField = value; } } /// <remarks/> [System.Xml.Serialization.XmlAnyElementAttribute(Order=5)] public System.Xml.XmlElement Any { get { return this.anyField; } set { this.anyField = value; } } }

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• How does the compile choose which template function to call?

  - by aCuria

  Regarding the below code, how does the compiler choose which template function to call? If the const T& function is omitted, the T& function is always called. If the T& function is omitted, the const T& function is always called. If both are included, the results are as below. #include <iostream> #include <typeinfo> template <typename T> void function(const T &t) { std::cout << "function<" << typeid(T).name() << ">(const T&) called with t = " << t << std::endl; } template <typename T> void function(T &t) { std::cout << "function<" << typeid(T).name() << ">(T&) called with t = " << t << std::endl; } int main() { int i1 = 57; const int i2 = -6; int *pi1 = &i1; int *const pi3 = &i1; const int *pi2 = &i2; const int *const pi4 = &i2; function(pi1); ///just a normal pointer -> T& function(pi2); ///cannot change what we point to -> T& function(pi3); ///cannot change where we point -> const T& function(pi4); ///cannot change everything -> const T& return 0; } /* g++ output: function<Pi>(T&) called with t = 0x22cd24 function<PKi>(T&) called with t = 0x22cd20 function<Pi>(const T&) called with t = 0x22cd24 function<PKi>(const T&) called with t = 0x22cd20 */ /* bcc32 output: function<int *>(T&) called with t = 0012FF50 function<const int *>(T&) called with t = 0012FF4C function<int *>(const T&) called with t = 0012FF50 function<const int *>(const T&) called with t = 0012FF4C */ /* cl output: function<int *>(T&) called with t = 0012FF34 function<int const *>(T&) called with t = 0012FF28 function<int *>(const T&) called with t = 0012FF34 function<int const *>(const T&) called with t = 0012FF28 */

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• Refactoring a leaf class to a base class, and keeping it also a interface implementation

  - by elcuco

  I am trying to refactor a working code. The code basically derives an interface class into a working implementation, and I want to use this implementation outside the original project as a standalone class. However, I do not want to create a fork, and I want the original project to be able to take out their implementation, and use mine. The problem is that the hierarchy structure is very different and I am not sure if this would work. I also cannot use the original base class in my project, since in reality it's quite entangled in the project (too many classes, includes) and I need to take care of only a subdomain of the problems the original project is. I wrote this code to test an idea how to implement this, and while it's working, I am not sure I like it: #include <iostream> // Original code is: // IBase -> Derived1 // I need to refactor Derive2 to be both indipendet class // and programmers should also be able to use the interface class // Derived2 -> MyClass + IBase // MyClass class IBase { public: virtual void printMsg() = 0; }; /////////////////////////////////////////////////// class Derived1 : public IBase { public: virtual void printMsg(){ std::cout << "Hello from Derived 1" << std::endl; } }; ////////////////////////////////////////////////// class MyClass { public: virtual void printMsg(){ std::cout << "Hello from MyClass" << std::endl; } }; class Derived2: public IBase, public MyClass{ virtual void printMsg(){ MyClass::printMsg(); } }; class Derived3: public MyClass, public IBase{ virtual void printMsg(){ MyClass::printMsg(); } }; int main() { IBase *o1 = new Derived1(); IBase *o2 = new Derived2(); IBase *o3 = new Derived3(); MyClass *o4 = new MyClass(); o1->printMsg(); o2->printMsg(); o3->printMsg(); o4->printMsg(); return 0; } The output is working as expected (tested using gcc and clang, 2 different C++ implementations so I think I am safe here): [elcuco@pinky ~/src/googlecode/qtedit4/tools/qtsourceview/qate/tests] ./test1 Hello from Derived 1 Hello from MyClass Hello from MyClass Hello from MyClass [elcuco@pinky ~/src/googlecode/qtedit4/tools/qtsourceview/qate/tests] ./test1.clang Hello from Derived 1 Hello from MyClass Hello from MyClass Hello from MyClass The question is My original code was: class Derived3: public MyClass, public IBase{ virtual void IBase::printMsg(){ MyClass::printMsg(); } }; Which is what I want to express, but this does not compile. I must admit I do not fully understand why this code work, as I expect that the new method Derived3::printMsg() will be an implementation of MyClass::printMsg() and not IBase::printMsg() (even tough this is what I do want). How does the compiler chooses which method to re-implement, when two "sister classes" have the same virtual function name? If anyone has a better way of implementing this, I would like to know as well :)

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• "C variable type sizes are machine dependent." Is it really true? signed & unsigned numbers ;

  - by claws

  Hello, I've been told that C types are machine dependent. Today I wanted to verify it. void legacyTypes() { /* character types */ char k_char = 'a'; //Signedness --> signed & unsigned signed char k_char_s = 'a'; unsigned char k_char_u = 'a'; /* integer types */ int k_int = 1; /* Same as "signed int" */ //Signedness --> signed & unsigned signed int k_int_s = -2; unsigned int k_int_u = 3; //Size --> short, _____, long, long long short int k_s_int = 4; long int k_l_int = 5; long long int k_ll_int = 6; /* real number types */ float k_float = 7; double k_double = 8; } I compiled it on a 32-Bit machine using minGW C compiler _legacyTypes: pushl %ebp movl %esp, %ebp subl $48, %esp movb $97, -1(%ebp) # char movb $97, -2(%ebp) # signed char movb $97, -3(%ebp) # unsigned char movl $1, -8(%ebp) # int movl $-2, -12(%ebp)# signed int movl $3, -16(%ebp) # unsigned int movw $4, -18(%ebp) # short int movl $5, -24(%ebp) # long int movl $6, -32(%ebp) # long long int movl $0, -28(%ebp) movl $0x40e00000, %eax movl %eax, -36(%ebp) fldl LC2 fstpl -48(%ebp) leave ret I compiled the same code on 64-Bit processor (Intel Core 2 Duo) on GCC (linux) legacyTypes: .LFB2: .cfi_startproc pushq %rbp .cfi_def_cfa_offset 16 movq %rsp, %rbp .cfi_offset 6, -16 .cfi_def_cfa_register 6 movb $97, -1(%rbp) # char movb $97, -2(%rbp) # signed char movb $97, -3(%rbp) # unsigned char movl $1, -12(%rbp) # int movl $-2, -16(%rbp)# signed int movl $3, -20(%rbp) # unsigned int movw $4, -6(%rbp) # short int movq $5, -32(%rbp) # long int movq $6, -40(%rbp) # long long int movl $0x40e00000, %eax movl %eax, -24(%rbp) movabsq $4620693217682128896, %rax movq %rax, -48(%rbp) leave ret Observations char, signed char, unsigned char, int, unsigned int, signed int, short int, unsigned short int, signed short int all occupy same no. of bytes on both 32-Bit & 64-Bit Processor. The only change is in long int & long long int both of these occupy 32-bit on 32-bit machine & 64-bit on 64-bit machine. And also the pointers, which take 32-bit on 32-bit CPU & 64-bit on 64-bit CPU. Questions: I cannot say, what the books say is wrong. But I'm missing something here. What exactly does "Variable types are machine dependent mean?" As you can see, There is no difference between instructions for unsigned & signed numbers. Then how come the range of numbers that can be addressed using both is different? I was reading http://stackoverflow.com/questions/2511246/how-to-maintain-fixed-size-of-c-variable-types-over-different-machines I didn't get the purpose of the question or their answers. What maintaining fixed size? They all are the same. I didn't understand how those answers are going to ensure the same size.

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• Give Markup support for Custom server control with public PlaceHolders properties

  - by ravinsp

  I have a custom server control with two public PlaceHolder properties exposed to outside. I can use this control in a page like this: <cc1:MyControl ID="MyControl1" runat="server"> <TitleTemplate> Title text and anything else </TitleTemplate> <ContentTemplate> <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> <asp:Button ID="Button1" runat="server" Text="Button" /> </ContentTemplate> </cc1:MyControl> TitleTemplate and ContentTemplate are properties of type asp.net PlaceHolder class. Everything works fine. The control gets any content given to these custom properties and produces a custom HTML output around them. If I want a Button1_Click event handler, I can attach the event handler in Page_Load like the following code. And it works. protected void Page_Load(object sender, EventArgs e) { Button1.Click += new EventHandler(Button1_Click); } void Button1_Click(object sender, EventArgs e) { TextBox1.Text = "Button1 clicked"; } But if try to attach the click event handler in aspx markup I get an error when running the application "Compiler Error Message: CS0117: 'ASP.default_aspx' does not contain a definition for 'Button1_Click' <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" /> AutoEventWireup is set to "true" in the page markup. This happens only for child controls inside my custom control. I can programatically access child control correctly. Only problem is with event handler assignment from Markup. When I select the child Button in markup, the properties window only detects it as a < BUTTON. Not System.Web.UI.Controls.Button. It also doesn't display the "Events" tab. How can I give markup support for this scenario? Here's code for MyControl class if needed. And remember, I'm not using any ITemplate types for this. The custom properties I provide are of type "PlaceHolder". [ToolboxData("<{0}:MyControl runat=server>" + "<TitleTemplate></TitleTemplate>" + "<ContentTemplate></ContentTemplate>" + "</{0}:MyControl>")] public class MyControl : WebControl { PlaceHolder contentTemplate, titleTemplate; public MyControl() { contentTemplate = new PlaceHolder(); titleTemplate = new PlaceHolder(); Controls.Add(contentTemplate); Controls.Add(titleTemplate); } [Browsable(true)] [TemplateContainer(typeof(PlaceHolder))] [PersistenceMode(PersistenceMode.InnerProperty)] public PlaceHolder TitleTemplate { get { return titleTemplate; } } [Browsable(true)] [TemplateContainer(typeof(PlaceHolder))] [PersistenceMode(PersistenceMode.InnerProperty)] public PlaceHolder ContentTemplate { get { return contentTemplate; } } protected override void RenderContents(HtmlTextWriter output) { output.Write("<div>"); output.Write("<div class=\"title\">"); titleTemplate.RenderControl(output); output.Write("</div>"); output.Write("<div class=\"content\">"); contentTemplate.RenderControl(output); output.Write("</div>"); output.Write("</div>"); } }

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• Overloading stream insertion without violating information hiding?

  - by Chris

  I'm using yaml-cpp for a project. I want to overload the << and >> operators for some classes, but I'm having an issue grappling with how to "properly" do this. Take the Note class, for example. It's fairly boring: class Note { public: // constructors Note( void ); ~Note( void ); // public accessor methods void number( const unsigned long& number ) { _number = number; } unsigned long number( void ) const { return _number; } void author( const unsigned long& author ) { _author = author; } unsigned long author( void ) const { return _author; } void subject( const std::string& subject ) { _subject = subject; } std::string subject( void ) const { return _subject; } void body( const std::string& body ) { _body = body; } std::string body( void ) const { return _body; } private: unsigned long _number; unsigned long _author; std::string _subject; std::string _body; }; The << operator is easy sauce. In the .h: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ); And in the .cpp: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ) { out << v.number() << v.author() << v.subject() << v.body(); return out; } No sweat. Then I go to declare the >> operator. In the .h: void operator >> ( const YAML::Node& node, Note& note ); But in the .cpp I get: void operator >> ( const YAML::Node& node, Note& note ) { node[0] >> ? node[1] >> ? node[2] >> ? node[3] >> ? return; } If I write things like node[0] >> v._number; then I would need to change the CV-qualifier to make all of the Note fields public (which defeats everything I was taught (by professors, books, and experience))) about data hiding. I feel like doing node[0] >> temp0; v.number( temp0 ); all over the place is not only tedious, error-prone, and ugly, but rather wasteful (what with the extra copies). Then I got wise: I attempted to move these two operators into the Note class itself, and declare them as friends, but the compiler (GCC 4.4) didn't like that: src/note.h:44: error: ‘YAML::Emitter& Note::operator<<(YAML::Emitter&, const Note&)’ must take exactly one argument src/note.h:45: error: ‘void Note::operator(const YAML::Node&, Note&)’ must take exactly one argument Question: How do I "properly" overload the >> operator for a class Without violating the information hiding principle? Without excessive copying?

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• GCC error with variadic templates: "Sorry, unimplemented: cannot expand 'Identifier...' into a fixe

  - by Dennis

  While doing variadic template programming in C++0x on GCC, once in a while I get an error that says "Sorry, unimplemented: cannot expand 'Identifier...' into a fixed-length arugment list." If I remove the "..." in the code then I get a different error: "error: parameter packs not expanded with '...'". So if I have the "..." in, GCC calls that an error, and if I take the "..." out, GCC calls that an error too. The only way I have been able to deal with this is to completely rewrite the template metaprogram from scratch using a different approach, and (with luck) I eventually come up with code that doesn't cause the error. But I would really like to know what I was doing wrong. Despite Googling for it and despite much experimentation, I can't pin down what it is that I'm doing differently between variadic template code that does produce this error, and code that does not have the error. The wording of the error message seems to imply that the code should work according the C++0x standard, but that GCC doesn't support it yet. Or perhaps it is a compiler bug? Here's some code that produces the error. Note: I don't need you to write a correct implementation for me, but rather just to point out what is about my code that is causing this specific error // Used as a container for a set of types. template <typename... Types> struct TypePack { // Given a TypePack<T1, T2, T3> and T=T4, returns TypePack<T1, T2, T3, T4> template <typename T> struct Add { typedef TypePack<Types..., T> type; }; }; // Takes the set (First, Others...) and, while N > 0, adds (First) to TPack. // TPack is a TypePack containing between 0 and N-1 types. template <int N, typename TPack, typename First, typename... Others> struct TypePackFirstN { // sorry, unimplemented: cannot expand ‘Others ...’ into a fixed-length argument list typedef typename TypePackFirstN<N-1, typename TPack::template Add<First>::type, Others...>::type type; }; // The stop condition for TypePackFirstN: when N is 0, return the TypePack that has been built up. template <typename TPack, typename... Others> struct TypePackFirstN<0, TPack, Others...> //sorry, unimplemented: cannot expand ‘Others ...’ into a fixed-length argument list { typedef TPack type; }; EDIT: I've noticed that while a partial template instantiation that looks like does incur the error: template <typename... T> struct SomeStruct<1, 2, 3, T...> {}; Rewriting it as this does not produce an error: template <typename... T> struct SomeStruct<1, 2, 3, TypePack<T...>> {}; It seems that you can declare parameters to partial specializations to be variadic; i.e. this line is OK: template <typename... T> But you cannot actually use those parameter packs in the specialization, i.e. this part is not OK: SomeStruct<1, 2, 3, T... The fact that you can make it work if you wrap the pack in some other type, i.e. like this: SomeStruct<1, 2, 3, TypePack<T...>> to me implies that the declaration of the variadic parameter to a partial template specialization was successful, and you just can't use it directly. Can anyone confirm this?

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• Singleton method not getting called in Cocos2d

  - by jini

  I am calling a Singleton method that does not get called when I try doing this. I get no errors or anything, just that I am unable to see the CCLOG message. Under what reasons would a compiler not give you error and not allow you to call a method? [[GameManager sharedGameManager] openSiteWithLinkType:kLinkTypeDeveloperSite]; The method is defined as follows: -(void)openSiteWithLinkType:(LinkTypes)linkTypeToOpen { CCLOG(@"WE ARE IN openSiteWithLinkType"); //I NEVER SEE THIS MESSAGE NSURL *urlToOpen = nil; if (linkTypeToOpen == kLinkTypeDeveloperSite) { urlToOpen = [NSURL URLWithString:@"http://somesite.com"]; } if (![[UIApplication sharedApplication]openURL:urlToOpen]) { CCLOG(@"%@%@",@"Failed to open url:",[urlToOpen description]); [self runSceneWithID:kMainMenuScene]; } } HERE IS THE CODE TO MY SINGLETON: #import "GameManager.h" #import "MainMenuScene.h" @implementation GameManager static GameManager* _sharedGameManager = nil; @synthesize isMusicON; @synthesize isSoundEffectsON; @synthesize hasPlayerDied; +(GameManager*) sharedGameManager { @synchronized([GameManager class]) { if (!_sharedGameManager) { [[self alloc] init]; return _sharedGameManager; } return nil; } } +(id)alloc { @synchronized ([GameManager class]) { NSAssert(_sharedGameManager == nil,@"Attempted to allocate a second instance of the Game Manager singleton"); _sharedGameManager = [super alloc]; return _sharedGameManager; } return nil; } -(id)init { self = [super init]; if (self != nil) { //Game Manager initialized CCLOG(@"Game Manager Singleton, init"); isMusicON = YES; isSoundEffectsON = YES; hasPlayerDied = NO; currentScene = kNoSceneUninitialized; } return self; } -(void) runSceneWithID:(SceneTypes)sceneID { SceneTypes oldScene = currentScene; currentScene = sceneID; id sceneToRun = nil; switch (sceneID) { case kMainMenuScene: sceneToRun = [MainMenuScene node]; break; default: CCLOG(@"Unknown Scene ID, cannot switch scenes"); return; break; } if (sceneToRun == nil) { //Revert back, since no new scene was found currentScene = oldScene; return; } //Menu Scenes have a value of < 100 if (sceneID < 100) { if (UI_USER_INTERFACE_IDIOM() != UIUserInterfaceIdiomPad) { CGSize screenSize = [CCDirector sharedDirector].winSizeInPixels; if (screenSize.width == 960.0f) { //iPhone 4 retina [sceneToRun setScaleX:0.9375f]; [sceneToRun setScaleY:0.8333f]; CCLOG(@"GM: Scaling for iPhone 4 (retina)"); } else { [sceneToRun setScaleX:0.4688f]; [sceneToRun setScaleY:0.4166f]; CCLOG(@"GM: Scaling for iPhone 3G or older (non-retina)"); } } } if ([[CCDirector sharedDirector] runningScene] == nil) { [[CCDirector sharedDirector] runWithScene:sceneToRun]; } else { [[CCDirector sharedDirector] replaceScene:sceneToRun]; } } -(void)openSiteWithLinkType:(LinkTypes)linkTypeToOpen { CCLOG(@"WE ARE IN openSiteWithLinkType"); NSURL *urlToOpen = nil; if (linkTypeToOpen == kLinkTypeDeveloperSite) { urlToOpen = [NSURL URLWithString:@"http://somesite.com"]; } if (![[UIApplication sharedApplication]openURL:urlToOpen]) { CCLOG(@"%@%@",@"Failed to open url:",[urlToOpen description]); [self runSceneWithID:kMainMenuScene]; } } -(void) test { CCLOG(@"this is test"); } @end

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• What am I doing wrong?, linking in C++

  - by Facon

  I'm trying to code a simple base64 encoder/decoder (to test my programming skill). I can compile it, but it doesn't link, I've this message error: C:\Documents and Settings\Facon\Escritoriog++ base64.o main.o -o prueba.exe main.o:main.cpp:(.text+0x24a): undefined reference to `Base64Encode(std::vector const&)' collect2: ld returned 1 exit status Compiler & Linker: Mingw32 3.4.5 SO: Windows XP This is my source code: base64.h: #ifndef BASE64_H #define BASE64_H #include <iostream> #include <vector> typedef unsigned char byte; std::string Base64Encode(const std::vector<byte> &array); std::vector<byte> Base64Decode(const std::string &array); #endif base64.cpp: #include "base64.h" std::string Base64Encode(std::vector<byte> &array) { const char *base64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; const unsigned int size = array.size(); std::string output; for (unsigned int i = 0; (i < size); i++) { if ((size - i) > 3) { output.push_back(static_cast<char>(base64_table[array[i] >> 2])); output.push_back(static_cast<char>(base64_table[((array[i++] & 0x03) << 4) | ((array[i] & 0xF0) >> 4)])); output.push_back(static_cast<char>(base64_table[((array[i++] & 0x0F) << 2) | ((array[i] & 0xC0) >> 4)])); output.push_back(static_cast<char>(base64_table[array[i] & 0x3F])); } else if ((size - i) == 3) { output.push_back(static_cast<char>(base64_table[array[i] >> 2])); output.push_back(static_cast<char>(base64_table[((array[i++] & 0x03) << 4) | ((array[i] & 0xF0) >> 4)])); output.push_back(static_cast<char>(base64_table[(array[i] & 0x0F) << 2])); output.push_back(static_cast<char>('=')); } else if ((size - i) == 2) { output.push_back(static_cast<char>(base64_table[array[i] >> 2])); output.push_back(static_cast<char>(base64_table[(array[i] & 0x03) << 4])); output.push_back('='); output.push_back('='); } } return output; } std::vector<byte> Base64Decode(const std::string &array) // TODO { const char *base64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; } main.cpp: #include <iostream> #include <vector> #include "base64.h" using namespace std; int main(int argc, char *argv[]) { const char* prueba = "sure."; vector<byte> texto; string codificado; for (unsigned int i = 0; (prueba[i] != 0); i++) { texto.push_back(prueba[i]); } codificado = Base64Encode(texto); cout << codificado; return 0; } PD: Sorry for my bad knowledge of English :P

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• Converting OCaml to F#: F# equivelent of Pervasives at_exit

  - by Guy Coder

  I am converting the OCaml Format module to F# and tracked a problem back to a use of the OCaml Pervasives at_exit. val at_exit : (unit -> unit) -> unit Register the given function to be called at program termination time. The functions registered with at_exit will be called when the program executes exit, or terminates, either normally or because of an uncaught exception. The functions are called in "last in, first out" order: the function most recently added with at_exit is called first. In the process of conversion I commented out the line as the compiler did not flag it as being needed and I was not expecting an event in the code. I checked the FSharp.PowerPack.Compatibility.PervasivesModule for at_exit using VS Object Browser and found none. I did find how to run code "at_exit"? and How do I write an exit handler for an F# application? The OCaml line is at_exit print_flush with print_flush signature: val print_flush : (unit -> unit) Also in looking at the use of it during a debug session of the OCaml code, it looks like at_exit is called both at the end of initialization and at the end of each use of a call to the module. Any suggestions, hints on how to do this. This will be my first event in F#. EDIT Here is some of what I have learned about the Format module that should shed some light on the problem. The Format module is a library of functions for basic pretty printer commands of simple OCaml values such as int, bool, string. The format module has commands like print_string, but also some commands to say put the next line in a bounded box, think new set of left and right margins. So one could write: print_string "Hello" or open_box 0; print_string "<<"; open_box 0; print_string "p \/ q ==> r"; close_box(); print_string ">>"; close_box() The commands such as open_box and print_string are handled by a loop that interprets the commands and then decides wither to print on the current line or advance to the next line. The commands are held in a queue and there is a state record to hold mutable values such as left and right margin. The queue and state needs to be primed, which from debugging the test cases against working OCaml code appears to be done at the end of initialization of the module but before the first call is made to any function in the Format module. The queue and state is cleaned up and primed again for the next set of commands by the use of mechanisms for at_exit that recognize that the last matching frame for the initial call to the format modules has been removed thus triggering the call to at_exit which pushes out any remaining command in the queue and re-initializes the queue and state. So the sequencing of the calls to print_flush is critical and appears to be at more than what the OCaml documentation states.

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• Problems with createImage(int width, int height)

  - by Jonathan

  I have the following code, which is run every 10ms as part of a game: private void gameRender() { if(dbImage == null) { //createImage() returns null if GraphicsEnvironment.isHeadless() //returns true. (java.awt.GraphicsEnvironment) dbImage = createImage(PWIDTH, PHEIGHT); if(dbImage == null) { System.out.println("dbImage is null"); //Error recieved return; } else dbg = dbImage.getGraphics(); } //clear the background dbg.setColor(Color.white); dbg.fillRect(0, 0, PWIDTH, PHEIGHT); //draw game elements... if(gameOver) { gameOverMessage(dbg); } } The problem is that it enters the if statement which checks for the Image being null, even after I attempt to define the image. I looked around, and it seems that createImage() will return null if GraphicsEnvironment.isHeadless() returns true. I don't understand exactly what the isHeadless() method's purpose is, but I thought it might have something to do with the compiler or IDE, so I tried on two, both of which get the same error (Eclipse, and BlueJ). Anyone have any idea what the source of the error is, and how I might fix it? Thanks in advance Jonathan ................................................................... EDIT: I am using java.awt.Component.createImage(int width, int height). The purpose of this method is to ensure the creation of, and edit an Image that will contain the view of the player of the game, that will later be drawn to the screen by means of a JPanel. Here is some more code if this helps at all: public class Sim2D extends JPanel implements Runnable { private static final int PWIDTH = 500; private static final int PHEIGHT = 400; private volatile boolean running = true; private volatile boolean gameOver = false; private Thread animator; //gameRender() private Graphics dbg; private Image dbImage = null; public Sim2D() { setBackground(Color.white); setPreferredSize(new Dimension(PWIDTH, PHEIGHT)); setFocusable(true); requestFocus(); //Sim2D now recieves key events readyForTermination(); addMouseListener( new MouseAdapter() { public void mousePressed(MouseEvent e) { testPress(e.getX(), e.getY()); } }); } //end of constructor private void testPress(int x, int y) { if(!gameOver) { gameOver = true; //end game at mousepress } } //end of testPress() private void readyForTermination() { addKeyListener( new KeyAdapter() { public void keyPressed(KeyEvent e) { int keyCode = e.getKeyCode(); if((keyCode == KeyEvent.VK_ESCAPE) || (keyCode == KeyEvent.VK_Q) || (keyCode == KeyEvent.VK_END) || ((keyCode == KeyEvent.VK_C) && e.isControlDown()) ) { running = false; //end process on above list of keypresses } } }); } //end of readyForTermination() public void addNotify() { super.addNotify(); //creates the peer startGame(); //start the thread } //end of addNotify() public void startGame() { if(animator == null || !running) { animator = new Thread(this); animator.start(); } } //end of startGame() //run method for world public void run() { while(running) { long beforeTime, timeDiff, sleepTime; beforeTime = System.nanoTime(); gameUpdate(); //updates objects in game (step event in game) gameRender(); //renders image paintScreen(); //paints rendered image to screen timeDiff = (System.nanoTime() - beforeTime) / 1000000; sleepTime = 10 - timeDiff; if(sleepTime <= 0) //if took longer than 10ms { sleepTime = 5; //sleep a bit anyways } try{ Thread.sleep(sleepTime); //sleep by allotted time (attempts to keep this loop to about 10ms) } catch(InterruptedException ex){} beforeTime = System.nanoTime(); } System.exit(0); } //end of run() private void gameRender() { if(dbImage == null) { dbImage = createImage(PWIDTH, PHEIGHT); if(dbImage == null) { System.out.println("dbImage is null"); return; } else dbg = dbImage.getGraphics(); } //clear the background dbg.setColor(Color.white); dbg.fillRect(0, 0, PWIDTH, PHEIGHT); //draw game elements... if(gameOver) { gameOverMessage(dbg); } } //end of gameRender() } //end of class Sim2D Hope this helps clear things up a bit, Jonathan

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• "Warning reaching end of non-void fuction" with Multiple Sections that pull in multiple CustomCells

  - by Newbyman

  I'm getting "Reaching end of non-void function" warning, but don't have anything else to return for the compiler. How do I get around the warning?? I'm using customCells to display a table with 3 Sections. Each CustomCell is different, linked with another viewcontroller's tableview within the App, and is getting its data from its individual model. Everything works great in the Simulator and Devices, but I would like to get rid of the warning that I have. It is the only one I have, and it is pending me from uploading to App Store!! Within the - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {, I have used 3 separate If() statements-(i.e.==0,==1,==2) to control which customCells are displayed within each section throughout the tableview's cells. Each of the customCells were created in IB, pull there data from different models, and are used with other ViewController tableViews. At the end of the function, I don't have a "cell" or anything else to return, because I already specified which CustomCell to return within each of the If() statements. Because each of the CustomCells are referenced through the AppDelegate, I can not set up an empty cell at the start of the function and just set the empty cell equal to the desired CustomCell within each of the If() statements, as you can for text, labels, etc... My question is not a matter of fixing code within the If() statements, unless it is required. My Questions is in "How to remove the warning for reaching end of non-void function-(cellForRowAtIndexPath:) when I have already returned a value for every possible case: if(section == 0); if(section == 1); and if(section == 2). *Code-Reference: The actual file names were knocked down for simplicity, (section 0 refers to M's, section 1 refers to D's, and section 2 refers to B's). Here is a sample Layout of the code: //CELL FOR ROW AT INDEX PATH: -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { //Reference to the AppDelegate: MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate]; //Section 0: if(indexPath.section == 0) { static NSString *CustomMCellIdentifier = @"CustomMCellIdentifier"; MCustomCell *mCell = (MCustomCell *)[tableView dequeueReusableCellWithIdentifier:CustomMCellIdentifier]; if (mCell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"MCustomCell" owner:tableView options:nil]; for (id oneObject in nib) if ([oneObject isKindOfClass:[MCustomCell class]]) mCell = (MCustomCell *)oneObject; } //Grab the Data for this item: M *mM = [appDelegate.mms objectAtIndex:indexPath.row]; //Set the Cell [mCell setM:mM]; mCell.selectionStyle =UITableViewCellSelectionStyleNone; mCell.root = tableView; return mCell; } //Section 1: if(indexPath.section == 1) { static NSString *CustomDCellIdentifier = @"CustomDCellIdentifier"; DCustomCell *dCell = (DCustomCell *)[tableView dequeueReusableCellWithIdentifier:CustomDaddyCellIdentifier]; if (dCell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"DCustomCell" owner:tableView options:nil]; for (id oneObject in nib) if ([oneObject isKindOfClass:[DCustomCell class]]) dCell = (DCustomCell *)oneObject; } //Grab the Data for this item: D *dD = [appDelegate.dds objectAtIndex:indexPath.row]; //Set the Cell [dCell setD:dD]; //Turns the Cell's SelectionStyle Blue Highlighting off, but still permits the code to run! dCell.selectionStyle =UITableViewCellSelectionStyleNone; dCell.root = tableView; return dCell; } //Section 2: if(indexPath.section == 2) { static NSString *CustomBCellIdentifier = @"CustomBCellIdentifier"; BCustomCell *bCell = (BCustomCell *)[tableView dequeueReusableCellWithIdentifier:CustomBCellIdentifier]; if (bCell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"BCustomCell" owner:tableView options:nil]; for (id oneObject in nib) if ([oneObject isKindOfClass:[BCustomCell class]]) bCell = (BCustomCell *)oneObject; } //Grab the Data for this item: B *bB = [appDelegate.bbs objectAtIndex:indexPath.row]; //Set the Cell [bCell setB:bB]; bCell.selectionStyle =UITableViewCellSelectionStyleNone; bCell.root = tableView; return bCell; } //** Getting Warning "Control reaches end of non-void function" //Not sure what else to "return ???" all CustomCells were specified within the If() statements above for their corresponding IndexPath.Sections. } Any Suggestions ??

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• C++ copy-construct construct-and-assign question

  - by Andy

  Blockquote Here is an extract from item 56 of the book "C++ Gotchas": It's not uncommon to see a simple initialization of a Y object written any of three different ways, as if they were equivalent. Y a( 1066 ); Y b = Y(1066); Y c = 1066; In point of fact, all three of these initializations will probably result in the same object code being generated, but they're not equivalent. The initialization of a is known as a direct initialization, and it does precisely what one might expect. The initialization is accomplished through a direct invocation of Y::Y(int). The initializations of b and c are more complex. In fact, they're too complex. These are both copy initializations. In the case of the initialization of b, we're requesting the creation of an anonymous temporary of type Y, initialized with the value 1066. We then use this anonymous temporary as a parameter to the copy constructor for class Y to initialize b. Finally, we call the destructor for the anonymous temporary. To test this, I did a simple class with a data member (program attached at the end) and the results were surprising. It seems that for the case of b, the object was constructed by the copy constructor rather than as suggested in the book. Does anybody know if the language standard has changed or is this simply an optimisation feature of the compiler? I was using Visual Studio 2008. Code sample: #include <iostream> class Widget { std::string name; public: // Constructor Widget(std::string n) { name=n; std::cout << "Constructing Widget " << this->name << std::endl; } // Copy constructor Widget (const Widget& rhs) { std::cout << "Copy constructing Widget from " << rhs.name << std::endl; } // Assignment operator Widget& operator=(const Widget& rhs) { std::cout << "Assigning Widget from " << rhs.name << " to " << this->name << std::endl; return *this; } }; int main(void) { // construct Widget a("a"); // copy construct Widget b(a); // construct and assign Widget c("c"); c = a; // copy construct! Widget d = a; // construct! Widget e = "e"; // construct and assign Widget f = Widget("f"); return 0; } Output: Constructing Widget a Copy constructing Widget from a Constructing Widget c Assigning Widget from a to c Copy constructing Widget from a Constructing Widget e Constructing Widget f Copy constructing Widget from f I was most surprised by the results of constructing d and e.

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• Const-correctness semantics in C++

  - by thirtythreeforty

  For fun and profit™, I'm writing a trie class in C++ (using the C++11 standard.) My trie<T> has an iterator, trie<T>::iterator. (They're all actually functionally const_iterators, because you cannot modify a trie's value_type.) The iterator's class declaration looks partially like this: template<typename T> class trie<T>::iterator : public std::iterator<std::bidirectional_iterator_tag, T> { friend class trie<T>; struct state { state(const trie<T>* const node, const typename std::vector<std::pair<typename T::value_type, std::unique_ptr<trie<T>>>>::const_iterator& node_map_it ) : node{node}, node_map_it{node_map_it} {} // This pointer is to const data: const trie<T>* node; typename std::vector<std::pair<typename T::value_type, std::unique_ptr<trie<T>>>>::const_iterator node_map_it; }; public: typedef const T value_type; iterator() =default; iterator(const trie<T>* node) { parents.emplace(node, node->children.cbegin()); // ... } // ... private: std::stack<state> parents; // ... }; Notice that the node pointer is declared const. This is because (in my mind) the iterator should not be modifying the node that it points to; it is just an iterator. Now, elsewhere in my main trie<T> class, I have an erase function that has a common STL signature--it takes an iterator to data to erase (and returns an iterator to the next object). template<typename T> typename trie<T>::iterator trie<T>::erase(const_iterator it) { // ... // Cannot modify a const object! it.parents.top().node->is_leaf = false; // ... } The compiler complains because the node pointer is read-only! The erase function definitely should modify the trie that the iterator points to, even though the iterator shouldn't. So, I have two questions: Should iterator's constructors be public? trie<T> has the necessary begin() and end() members, and of course trie<T>::iterator and trie<T> are mutual friends, but I don't know what the convention is. Making them private would solve a lot of the angst I'm having about removing the const "promise" from the iterator's constructor. What are the correct const semantics/conventions regarding the iterator and its node pointer here? Nobody has ever explained this to me, and I can't find any tutorials or articles on the Web. This is probably the more important question, but it does require a good deal of planning and proper implementation. I suppose it could be circumvented by just implementing 1, but it's the principle of the thing!

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• Error inserting data in binary tree

  - by chepe263

  I copied this code (in spanish) http://www.elrincondelc.com/nuevorincon/index.php?pag=codigos&id=4 and wrote a new one. This is my code: #include <cstdlib> #include <conio.h> #include <iostream> using namespace std; struct nodoarbol { int dato; struct nodoarbol *izq; struct nodoarbol *der; }; typedef nodoarbol Nodo; typedef Nodo *Arbol; void insertar(Arbol *, int); void inorden(Arbol); void postorden(Arbol); void preorden(Arbol); void insertar(Arbol *raiz, int nuevo){ if (*raiz==NULL){ *raiz = (Nodo *)malloc(sizeof(Nodo)); if (*raiz != NULL){ (*raiz)->dato=nuevo; (*raiz)->der=NULL; (*raiz)->izq=NULL; } else{ cout<<"No hay memoria suficiente u ocurrio un error"; } } else{ if (nuevo < (*raiz)->dato) insertar( &((*raiz)->izq), nuevo ); else if (nuevo > (*raiz)->dato) insertar(&((*raiz)->der), nuevo); } }//inseertar void inorden(Arbol raiz){ if (raiz != NULL){ inorden(raiz->izq); cout << raiz->dato << " "; inorden(raiz->der); } } void preorden(Arbol raiz){ if (raiz != NULL){ cout<< raiz->dato << " "; preorden(raiz->izq); preorden(raiz->der); } } void postorden(Arbol raiz){ if (raiz!=NULL){ postorden(raiz->izq); postorden(raiz->der); cout<<raiz->dato<<" "; } } int main() { int i; i=0; int val; Arbol raiz = NULL; for (i=0; i<10; i++){ cout<<"Inserte un numero"; cin>>val; insertar( (raiz), val); } cout<<"\nPreorden\n"; preorden(raiz); cout<<"\nIneorden\n"; inorden(raiz); cout<<"\nPostorden\n"; postorden(raiz); return 0; } I'm using netbeans 7.1.1, mingw32 compiler This is the output: make[2]: Leaving directory `/q/netbeans c++/NetBeansProjects/treek' make[1]: Leaving directory `/q/netbeans c++/NetBeansProjects/treek' main.cpp: In function 'int main()': main.cpp:110:30: error: cannot convert 'Arbol {aka nodoarbol*}' to 'Nodo** {aka nodoarbol**}' for argument '1' to 'void insertar(Nodo**, int)' make[2]: *** [build/Release/MinGW-Windows/main.o] Error 1 make[1]: *** [.build-conf] Error 2 make: *** [.build-impl] Error 2 BUILD FAILED (exit value 2, total time: 11s) I don't understand what's wrong since i just copied the code (and rewrite it to my own code). I'm really good in php, asp.net (vb) and other languages but c is a headche for me. I've been struggling with this problem for about an hour. Could somebody tell me what could it be?

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• C++ Optimize if/else condition

  - by Heye

  I have a single line of code, that consumes 25% - 30% of the runtime of my application. It is a less-than comparator for an std::set (the set is implemented with a Red-Black-Tree). It is called about 180 Million times within 52 seconds. struct Entry { const float _cost; const long _id; // some other vars Entry(float cost, float id) : _cost(cost), _id(id) { } }; template<class T> struct lt_entry: public binary_function <T, T, bool> { bool operator()(const T &l, const T &r) const { // Most readable shape if(l._cost != r._cost) { return r._cost < l._cost; } else { return l._id < r._id; } } }; The entries should be sorted by cost and if the cost is the same by their id. I have many insertions for each extraction of the minimum. I thought about using Fibonacci-Heaps, but I have been told that they are theoretically nice, but suffer from high constants and are pretty complicated to implement. And since insert is in O(log(n)) the runtime increase is nearly constant with large n. So I think its okay to stick to the set. To improve performance I tried to express it in different shapes: return l._cost < r._cost || r._cost > l._cost || l._id < r._id; return l._cost < r._cost || (l._cost == r._cost && l._id < r._id); Even this: typedef union { float _f; int _i; } flint; //... flint diff; diff._f = (l._cost - r._cost); return (diff._i && diff._i >> 31) || l._id < r._id; But the compiler seems to be smart enough already, because I haven't been able to improve the runtime. I also thought about SSE but this problem is really not very applicable for SSE... The assembly looks somewhat like this: movss (%rbx),%xmm1 mov $0x1,%r8d movss 0x20(%rdx),%xmm0 ucomiss %xmm1,%xmm0 ja 0x410600 <_ZNSt8_Rb_tree[..]+96> ucomiss %xmm0,%xmm1 jp 0x4105fd <_ZNSt8_Rb_[..]_+93> jne 0x4105fd <_ZNSt8_Rb_[..]_+93> mov 0x28(%rdx),%rax cmp %rax,0x8(%rbx) jb 0x410600 <_ZNSt8_Rb_[..]_+96> xor %r8d,%r8d I have a very tiny bit experience with assembly language, but not really much. I thought it would be the best (only?) point to squeeze out some performance, but is it really worth the effort? Can you see any shortcuts that could save some cycles? The platform the code will run on is an ubuntu 12 with gcc 4.6 (-stl=c++0x) on a many-core intel machine. Only libraries available are boost, openmp and tbb. I am really stuck on this one, it seems so simple, but takes that much time. I have been crunching my head since days thinking how I could improve this line... Can you give me a suggestion how to improve this part, or is it already at its best?

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• jsp getServletContext() error

  - by Reigel

  html <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Murach's Java Servlets and JSP</title> </head> <body> <%-- import packages and classes needed by the scripts --%> <%@ page import="business.*, data.*" %> <% //get parameters from the request String firstName = request.getParameter("firstName"); String lastName = request.getParameter("lastName"); String emailAddress = request.getParameter("emailAddress"); // get the real path for the EmailList.txt file ServletContext sc = this.getServletContext(); String path = sc.getRealPath("/WEB-INF/EmailList.txt"); // use regular Java objects User user = new User(firstName, lastName, emailAddress); UserIO.add(user, path); %> <h1>Thanks for joining our email list</h1> <p>Here is the information that you entered: </p> <table cellspacing="5" cellpadding="5" border="1"> <tr> <td align="right">First name:</td> <td><%= firstName %></td> </tr> <tr> <td align="right">Last name:</td> <td><%= lastName %></td> </tr> <tr> <td align="right">Email Address:</td> <td><%= emailAddress %></td> </tr> </table> <p>To enter another email address, click on the Back <br /> button in your browser or the Return button shown <br /> below.</p> <form action="index.jsp" method="post"> <input type="submit" value="Return" /> </form> </body> </html> and it's giving me this error page... Compilation of 'C:\bea\user_projects\domains\mydomain.\myserver.wlnotdelete\extract\myserver_sample01_WebContent\jsp_servlet__display_email_entry.java' failed: C:\bea\user_projects\domains\mydomain.\myserver.wlnotdelete\extract\myserver_sample01_WebContent\jsp_servlet__display_email_entry.java:140: cannot resolve symbol probably occurred due to an error in /display_email_entry.jsp line 19: ServletContext sc = this.getServletContext(); Full compiler error(s): C:\bea\user_projects\domains\mydomain.\myserver.wlnotdelete\extract\myserver_sample01_WebContent\jsp_servlet__display_email_entry.java:140: cannot resolve symbol symbol : method getServletContext () location: class jsp_servlet.__display_email_entry     ServletContext sc = this.getServletContext(); //[ /display_email_entry.jsp; Line:19]                                    ^ 1 error Thu Jun 03 15:56:09 CST 2010 any hint? I'm really new to JSP, and this is my first learning practice... can't find it by google.com.... thanks!

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• Problem with incomplete type while trying to detect existence of a member function

  - by abir

  I was trying to detect existence of a member function for a class where the function tries to use an incomplete type. The typedef is struct foo; typedef std::allocator<foo> foo_alloc; The detection code is struct has_alloc { template<typename U,U x> struct dummy; template<typename U> static char check(dummy<void* (U::*)(std::size_t),&U::allocate>*); template<typename U> static char (&check(...))[2]; const static bool value = (sizeof(check<foo_alloc>(0)) == 1); }; So far I was using incomplete type foo with std::allocator without any error on VS2008. However when I replaced it with nearly an identical implementation as template<typename T> struct allocator { T* allocate(std::size_t n) { return (T*)operator new (sizeof(T)*n); } }; it gives an error saying that as T is incomplete type it has problem instantiating allocator<foo> because allocate uses sizeof. GCC 4.5 with std::allocator also gives the error, so it seems during detection process the class need to be completely instantiated, even when I am not using that function at all. What I was looking for is void* allocate(std::size_t) which is different from T* allocate(std::size_t). My questions are (I have three questions, but as they are correlated , so I thought it is better not to create three separate questions). Why MS std::allocator doesn't check for incomplete type foo while instantiating? Are they following any trick which can be implemented ? Why the compiler need to instantiate allocator<T> to check the existence of the function when sizeof is not used as sfinae mechanism to remove/add allocate in the overload resolutions set? It should be noted that, if I remove the generic implementation of allocate leaving the declaration only, and specialized it for foo afterwards such as struct foo{}; template< struct allocator { foo* allocate(std::size_t n) { return (foo*)operator new (sizeof(foo)*n); } }; after struct has_alloc it compiles in GCC 4.5 while gives error in VS2008 as allocator<T> is already instantiated and explicit specialization for allocator<foo> already defined. Is it legal to use nested types for an std::allocator of incomplete type such as typedef foo_alloc::pointer foo_pointer; ? Though it is practically working for me, I suspect the nested types such as pointer may depend on completeness of type it takes. It will be good to know if there is any possible way to typedef such types as foo_pointer where the type pointer depends on completeness of foo. NOTE : As the code is not copy paste from editor, it may have some syntax error. Will correct it if I find any. Also the codes (such as allocator) are not complete implementation, I simplified and typed only the portion which I think useful for this particular problem.

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• Reordering Variadic Parameters

  - by void-pointer

  I have come across the need to reorder a variadic list of parameters that is supplied to the constructor of a struct. After being reordered based on their types, the parameters will be stored as a tuple. My question is how this can be done so that a modern C++ compiler (e.g. g++-4.7) will not generate unnecessary load or store instructions. That is, when the constructor is invoked with a list of parameters of variable size, it efficiently pushes each parameter into place based on an ordering over the parameters' types. Here is a concrete example. Assume that the base type of every parameter (without references, rvalue references, pointers, or qualifiers) is either char, int, or float. How can I make it so that all the parameters of base type char appear first, followed by all of those of base type int (which leaves the parameters of base type float last). The relative order in which the parameters were given should not be violated within sublists of homogeneous base type. Example: foo::foo() is called with arguments float a, char&& b, const float& c, int&& d, char e. The tuple tupe is std::tuple<char, char, int, float, float>, and it is constructed like so: tuple_type{std::move(b), e, std::move(d), a, c}. Consider the struct defined below, and assume that the metafunction deduce_reordered_tuple_type is already implemented. How would you write the constructor so that it works as intended? If you think that the code for deduce_reodered_tuple_type, would be useful to you, I can provide it; it's a little long. template <class... Args> struct foo { // Assume that the metafunction deduce_reordered_tuple_type is defined. typedef typename deduce_reordered_tuple_type<Args...>::type tuple_type; tuple_type t_; foo(Args&&... args) : t_{reorder_and_forward_parameters<Args>(args)...} {} }; Edit 1 The technique I describe above does have applications in mathematical frameworks that make heavy use of expression templates, variadic templates, and metaprogramming in order to perform aggressive inlining. Suppose that you wish to define an operator that takes the product of several expressions, each of which may be passed by reference, reference to const, or rvalue reference. (In my case, the expressions are conditional probability tables and the operation is the factor product, but something like matrix multiplication works suitably as well.) You need access to the data provided by each expression in order to evaluate the product. Consequently, you must move the expressions passed as rvalue references, copy the expressions passed by reference to const, and take the addresses of expressions passed by reference. Using the technique I describe above now poses several benefits. Other expressions can use uniform syntax to access data elements from this expression, since all of the heavy-lifting metaprogramming work is done beforehand, within the class. We can save stack space by grouping the pointers together and storing the larger expressions towards the end of the tuple. Implementing certain types of queries becomes much easier (e.g. check whether any of the pointers stored in the tuple aliases a given pointer). Thank you very much for your help!

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