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• On null pointer arg, better to crash or throw exception?

  - by paz

  What is the preferred way to handle a null pointer passed in as an output argument to a function? I could ASSERT but I feel like its not good to let a library crash the program. Instead, I was thinking about using exceptions.

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• Simple Java Sound Applet won't work!!! ARG!!!

  - by William

  import java.applet.*; /** * SoundApplet.java - a simple applet that plays the "gong.au" sound file. */ public class AppletGame extends Applet { public void init() { super.init(); resize(0,0); AudioClip gong = getAudioClip(getDocumentBase(), "test0.au"); gong.play(); } } In Eclipse applet viewer it loads and doesn't play sound. In html it doesn't load and says start not initalized. I've tried calling it outside of init, and all that someone help me!!!

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• C++ Pass a hidden arg to a class constructor?

  - by JP

  I would like to define a class that accept the pointer to it's parent class as an Argument, but would it be possible to somehow pass it without needing to pass it directly such as: class Child { public: Child(Parent* hiddenArg); }; class Parent { public: Child myChild; }; I know this is weird, but I am making my own Signal/Slot implementation and Child would be a signal defined, but I would like to get the parent so I can use it's Event Dispatcher...

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• Difference between std::result_of and decltype

  - by Luc Touraille

  I have some trouble understanding the need for std::result_of in C++0x. If I understood correctly, result_of is used to obtain the resulting type of invoking a function object with certain types of parameters. For example: template <typename F, typename Arg> typename std::result_of<F(Arg)> invoke(F f, Arg a) { return f(a); } I don't really see the difference with the following code: template <typename F, typename Arg> auto invoke(F f, Arg a) -> decltype(f(a)) //uses the f parameter { return f(a); } or template <typename F, typename Arg> auto invoke(F f, Arg a) -> decltype(F()(a)); //"constructs" an F { return f(a); } The only problem I can see with these two solutions is that we need to either: have an instance of the functor to use it in the expression passed to decltype. know a defined constructor for the functor. Am I right in thinking that the only difference between decltype and result_of is that the first one needs an expression whereas the second does not?

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• C#: Specify that a function arg must inhert from one class, and implement an interface?

  - by Rosarch

  I'm making a game where each Actor is represented by a GameObjectController. Game Objects that can partake in combat implement ICombatant. How can I specify that arguments to a combat function must inherit from GameObjectController and implement ICombatant? Or does this indicate that my code is structured poorly? public void ComputeAttackUpdate(ICombatant attacker, AttackType attackType, ICombatant victim) In the above code, I want attacker and victim to inherit from GameObjectController and implement ICombatant. Is this syntactically possible?

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• C++: Declaration of template class member specialization (+ Doxygen bonus question!)

  - by Ziv

  When I specialize a (static) member function/constant in a template class, I'm confused as to where the declaration is meant to go. Here's an example of what I what to do - yoinked directly from IBM's reference on template specialization: template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } int main() { X<char*> a, b; X<float> c; c.f(10); // X<float>::v now set to 20 } The question is, how do I divide this into header/cpp files? The generic implementation is obviously in the header, but what about the specialization? It can't go in the header file, because it's concrete, leading to multiple definition. But if it goes into the .cpp file, is code which calls X::f() aware of the specialization, or might it rely on the generic X::f()? So far I've got the specialization in the .cpp only, with no declaration in the header. I'm not having trouble compiling or even running my code (on gcc, don't remember the version at the moment), and it behaves as expected - recognizing the specialization. But A) I'm not sure this is correct, and I'd like to know what is, and B) my Doxygen documentation comes out wonky and very misleading (more on that in a moment). What seems most natural to me would be something like this, declaring the specialization in the header and defining it in the .cpp: ===XClass.hpp=== #ifndef XCLASS_HPP #define XCLASS_HPP template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } /* declaration of specialized functions */ template<> char* X<char*>::v; template<> void X<float>::f(float arg); #endif ===XClass.cpp=== #include <XClass.hpp> /* concrete implementation of specialized functions */ template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } ...but I have no idea if this is correct. The most immediate consequence of this issue, as I mentioned, is my Doxygen documentation, which doesn't seem to warm to the idea of member specialization, at least the way I'm defining it at the moment. It will always present only the first definition it finds of a function/constant, and I really need to be able to present the specializations as well. If I go so far as to re-declare the entire class, i.e. in the header: /* template declaration */ template<class T> class X { public: static T v; static void f(T); }; /* template member definition */ template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } /* declaration of specialized CLASS (with definitions in .cpp) */ template<> class X<float> { public: static float v; static void f(float); }; then it will display the different variations of X as different classes (which is fine by me), but I don't know how to get the same effect when specializing only a few select members of the class. I don't know if this is a mistake of mine, or a limitation of Doxygen - any ideas? Thanks much, Ziv

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• JQuery error: XML filter is applied to non-XML value (function (E, F) {return new (o.fn.init)(E, F);

  - by morpheous

  I am getting this slightly cryptic error message: XML filter is applied to non-XML value (function (E, F) {return new (o.fn.init)(E, F);}) when I run this code snippet function justDoIt(arg){ msg = arg.msg; if(arg.ok) jQuery.(".action-button").each(function(idx,el){jQuery(this).removeClass('enabled');} ); } arg is a JSON format response form the server. Anyone knows how to fix this?

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• How should I check that a given argument is a datetime.date object?

  - by rmh

  I'm currently using an assert statement with isinstance. Because datetime is a subclass of date, I also need to check that it isn't an instance of datetime. Surely there's a better way? from datetime import date, datetime def some_func(arg): assert isinstance(arg, date) and not isinstance(arg, datetime),\ 'arg must be a datetime.date object' # ...

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• Proper exceptions to use for nulls

  - by user200295

  In the following example we have two different exceptions we want to communicate. //constructor public Main(string arg){ if(arg==null) throw new ArgumentNullException("arg"); Thing foo=GetFoo(arg); if(foo==null) throw new NullReferenceException("foo is null"); } Is this the proper approach for both exception types?

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• What is the difference between client side testing versus server side testing when we are execute va

  - by HTMLCSS_noob

  hi all, as per my question, i am wondering what differences are there when we are performing tests for the client side , as compared to performing tests on the client side? For example, testing javascript on the client side versus testing server side code? Best Regards.

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• When declaring a function in C++/CLI, what is the meaning of the signs ^ and * before and after a va

  - by Shlomi Assaf

  For example: Let's say we have a class called MyClass. String^ MyClass::GetSomeInfoForExamplePuprs( int InfoNumber ) { } or static String ^GetOtherInfoExample() { } or String ^GetOtherInfoExample(object *Something) { } I saw it in source code and can't figure it out.

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• C++ invalid reference problem

  - by Karol

  Hi all, I'm writing some callback implementation in C++. I have an abstract callback class, let's say: /** Abstract callback class. */ class callback { public: /** Executes the callback. */ void call() { do_call(); }; protected: /** Callback call implementation specific to derived callback. */ virtual void do_call() = 0; }; Each callback I create (accepting single-argument functions, double-argument functions...) is created as a mixin using one of the following: /** Makes the callback a single-argument callback. */ template <typename T> class singleArgumentCallback { protected: /** Callback argument. */ T arg; public: /** Constructor. */ singleArgumentCallback(T arg): arg(arg) { } }; /** Makes the callback a double-argument callback. */ template <typename T, typename V> class doubleArgumentCallback { protected: /** Callback argument 1. */ T arg1; /** Callback argument 2. */ V arg2; public: /** Constructor. */ doubleArgumentCallback(T arg1, V arg2): arg1(arg1), arg2(arg2) { } }; For example, a single-arg function callback would look like this: /** Single-arg callbacks. */ template <typename T> class singleArgFunctionCallback: public callback, protected singleArgumentCallback<T> { /** Callback. */ void (*callbackMethod)(T arg); public: /** Constructor. */ singleArgFunctionCallback(void (*callback)(T), T argument): singleArgumentCallback<T>(argument), callbackMethod(callback) { } protected: void do_call() { this->callbackMethod(this->arg); } }; For user convenience, I'd like to have a method that creates a callback without having the user think about details, so that one can call (this interface is not subject to change, unfortunately): void test3(float x) { std::cout << x << std::endl; } void test5(const std::string& s) { std::cout << s << std::endl; } make_callback(&test3, 12.0f)->call(); make_callback(&test5, "oh hai!")->call(); My current implementation of make_callback(...) is as follows: /** Creates a callback object. */ template <typename T, typename U> callback* make_callback( void (*callbackMethod)(T), U argument) { return new singleArgFunctionCallback<T>(callbackMethod, argument); } Unfortunately, when I call make_callback(&test5, "oh hai!")->call(); I get an empty string on the standard output. I believe the problem is that the reference gets out of scope after callback initialization. I tried using pointers and references, but it's impossible to have a pointer/reference to reference, so I failed. The only solution I had was to forbid substituting reference type as T (for example, T cannot be std::string&) but that's a sad solution since I have to create another singleArgCallbackAcceptingReference class accepting a function pointer with following signature: void (*callbackMethod)(T& arg); thus, my code gets duplicated 2^n times, where n is the number of arguments of a callback function. Does anybody know any workaround or has any idea how to fix it? Thanks in advance!

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• Flex Builder debug problem

  - by Chetan Sachdev

  I am running on Windows XP and recently updated Flash Player from v9 to v10.1. And Now, in the Debug Console under Flex Builder, I am getting a lot of debug statements(I think that is assembly). Below is an example, of what I get: " active: eax(737-757) ecx(738-758) ebx(3-797) esi(728-756) @739 st 143112124(0) <- @3 09002830 mov 143112124(0), ebx active: eax(737-757) ecx(738-758) ebx(3-797) esi(728-756) @740 ldop 0(@3) 09002836 mov edx, 0(ebx) active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) @741 ldop 20(@740) 09002838 mov edi, 20(edx) active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(741-742) * @742 lea 4(@741) spans call 0900283B lea edi, 4(edi) active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @743 st 143111460(0) <- @742 0900283E mov 143111460(0), edi active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @744 alloc 12 alloca 12 at 120 for @744 activation.size 132 stacksize 132 entries 17 -8(ebp) (6-792) alloc -20(ebp) (7-792) alloc -68(ebp) (8-792) alloc -72(ebp) (0-793) arg -76(ebp) (16-797) def -80(ebp) (440-797) def -80(ebp) -84(ebp) -88(ebp) (1-793) arg -92(ebp) -96(ebp) -100(ebp) (2-793) arg -104(ebp) -112(ebp) -116(ebp) -120(ebp) -132(ebp) (744-760) alloc active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @745 imm 2 active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @746 st 0(@744) <- @745 09002844 mov -132(ebp), 2 active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @747 imm 139523392 active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @748 st 4(@744) <- @747 0900284E mov -128(ebp), 139523392 active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @749 imm 136426472 active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @750 st 8(@744) <- @749 09002855 mov -124(ebp), 136426472 active: eax(737-757) ecx(738-758) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @751 ldop 16(@738) STEAL any @738 alloca 4 at 80 for @738 activation.size 132 stacksize 132 entries 17 -8(ebp) (6-792) alloc -20(ebp) (7-792) alloc -68(ebp) (8-792) alloc -72(ebp) (0-793) arg -76(ebp) (16-797) def -80(ebp) (440-797) def -80(ebp) -84(ebp) (738-758) use -88(ebp) (1-793) arg -92(ebp) -96(ebp) -100(ebp) (2-793) arg -104(ebp) -112(ebp) -116(ebp) -120(ebp) -132(ebp) (744-760) alloc 0900285C mov -84(ebp), ecx 0900285F mov ecx, 16(ecx) active: eax(737-757) ecx(751-759) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @752 imm 1 active: eax(737-757) ecx(751-759) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * @753 or @738 @752 STEAL any @751 alloca 4 at 88 for @751 activation.size 132 stacksize 132 entries 17 -8(ebp) (6-792) alloc -20(ebp) (7-792) alloc -68(ebp) (8-792) alloc -72(ebp) (0-793) arg -76(ebp) (16-797) def -80(ebp) (440-797) def -80(ebp) -84(ebp) (738-758) use -88(ebp) (1-793) arg -92(ebp) (751-759) ldop -96(ebp) -100(ebp) (2-793) arg -104(ebp) -112(ebp) -116(ebp) -120(ebp) -132(ebp) (744-760) alloc 09002862 mov -92(ebp), ecx 09002865 mov ecx, -84(ebp) 09002868 or ecx, 1 active: eax(737-757) ecx(753-759) edx(740-754) ebx(3-797) esi(728-756) edi(742-769) * " I am not sure, why it started, but any help will be appreciated.

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• C++: Declaration of template class member specialization

  - by Ziv

  When I specialize a (static) member function/constant in a template class, I'm confused as to where the declaration is meant to go. Here's an example of what I what to do - yoinked directly from IBM's reference on template specialization: ===IBM Member Specialization Example=== template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } int main() { X<char*> a, b; X<float> c; c.f(10); // X<float>::v now set to 20 } The question is, how do I divide this into header/cpp files? The generic implementation is obviously in the header, but what about the specialization? It can't go in the header file, because it's concrete, leading to multiple definition. But if it goes into the .cpp file, is code which calls X::f() aware of the specialization, or might it rely on the generic X::f()? So far I've got the specialization in the .cpp only, with no declaration in the header. I'm not having trouble compiling or even running my code (on gcc, don't remember the version at the moment), and it behaves as expected - recognizing the specialization. But A) I'm not sure this is correct, and I'd like to know what is, and B) my Doxygen documentation comes out wonky and very misleading (more on that in a moment a later question). What seems most natural to me would be something like this, declaring the specialization in the header and defining it in the .cpp: ===XClass.hpp=== #ifndef XCLASS_HPP #define XCLASS_HPP template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } /* declaration of specialized functions */ template<> char* X<char*>::v; template<> void X<float>::f(float arg); #endif ===XClass.cpp=== #include <XClass.hpp> /* concrete implementation of specialized functions */ template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } ...but I have no idea if this is correct. Any ideas? Thanks much, Ziv

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• Python key word arguments

  - by pythonic metaphor

  I have several layers of function calls, passing around a common dictionary of key word arguments: def func1(**qwargs): func2(**qwargs) func3(**qwargs) I would like to supply some default arguments in some of the subsequent function calls, something like this: def func1(**qwargs): func2(arg = qwargs.get("arg", default), **qwargs) func3(**qwargs) The problem with this approach is that if arg is inside qwargs, a TypeError is raised with "got multiple values for keyword argument". I don't want to set qwargs["arg"] to default, because then func3 gets this argument without warrant. I could make a copy.copy of the qwargs and set "arg" in the copy, but qwargs could have large data structures in it and I don't want to copy them (maybe copy.copy wouldn't, only copy.deepcopy?). What's the pythonic thing to do here?

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• the problem about different treatment to __VA_ARGS__ when using VS 2008 and GCC

  - by liuliu

  I am trying to identify a problem because of an unusual usage of variadic macros. Here is the hypothetic macro: #define va(c, d, ...) c(d, __VA_ARGS__) #define var(a, b, ...) va(__VA_ARGS__, a, b) var(2, 3, printf, “%d %d %d\n”, 1); For gcc, the preprocessor will output printf("%d %d %d\n", 1, 2, 3) but for VS 2008, the output is printf, “%d %d %d\n”, 1(2, 3); I suspect the difference is caused by the different treatment to VA_ARGS, for gcc, it will first expand the expression to va(printf, "%d %d %d\n", 1, 2, 3), and treat 1, 2, 3 as the VA_ARGS for macro va. But for VS 2008, it will first treat b as VA_ARGS for macro va, and then do the expansion. Which one is correct interpretation for C99 variadic macro? or my usage falls into an undefined behavior?

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• Javascript instanceof & typeof in GWT (JSNI)

  - by rybz

  Hi, I've encountered an curious problem while trying to use some objects through JSNI in GWT. Let's say we have javscript file with the function defined: test.js: function test(arg){ var type = typeof(arg); if (arg instanceof Array) alert('Array'); if (arg instanceof Object) alert('Object'); if (arg instanceof String) alert('String'); } And the we want to call this function user JSNI: public static native void testx()/ *-{ $wnd.test( new Array(1, 2, 3) ); $wnd.test( [ 1, 2, 3 ] ); $wnd.test( {val:1} ); $wnd.test( "Some text" ); }-*/; The questions are: why instanceof instructions will always return false? why typeof will always return "object" ? how to pass these objects so that they were recognized properly?

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• How to debug/reformat C printf calls with lots of arguments in vim?

  - by Costi

  I have a function call in a program that I'm maintaining has 28 arguments for a printf call. It's printing a lot of data in a CSV file. I have problems following finding where what goes and I have some mismatches in the parameters types. I enabled -Wall in gcc and I get warnings like: n.c:495: warning: int format, pointer arg (arg 15) n.c:495: warning: format argument is not a pointer (arg 16) n.c:495: warning: double format, pointer arg (arg 23) The function is like this: fprintf (ConvFilePtr, "\"FORMAT3\"%s%04d%s%04d%s%s%s%d%s%c%s%d%c%s%s%s%s%s%s%s%11.lf%s%11.lf%s%11.lf%s%d\n", some_28_arguments_go_here); I would like to know if there is a vim plugin that highlights the printf format specifier when i go with the cursor over a variable. Other solutions? How to better reformat the code to make it more readable?

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• Return from parent sub in Perl

  - by JS Bangs

  I want to write a subroutine which causes the caller to return under certain conditions. This is meant to be used as a shortcut for validating input to a function. What I have so far is: sub needs($$) { my ($condition, $message) = @_; if (not $condition) { print "$message\n"; # would like to return from the *parent* here } return $condition; } sub run_find { my $arg = shift @_; needs $arg, "arg required" or return; needs exists $lang{$arg}, "No such language: $arg" or return; # etc. } The advantage of returning from the caller in needs would then be to avoid having to write the repetitive or return inside run_find and similar functions.

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• Translate from c# to c++

  - by Xaver

  Help to translate from c# code to c++ code. Type tp = Type.GetTypeFromProgID("Shell.Application"); object o = Activator.CreateInstance(tp); Object[] arg = new Object[1]; arg[0] = "C:\\!!"; object b = o.GetType().InvokeMember(@"NameSpace", BindingFlags.Public | BindingFlags.InvokeMethod, null, o, arg); arg[0] = "ftp://anonymous:[email protected]/bussys/1394"; b.GetType().InvokeMember(@"CopyHere", BindingFlags.Public | BindingFlags.InvokeMethod, null, b, arg);

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• How can I put a string and an integer into the same array?

  - by Stelios M

  I have to following code. I want this to return an array e.g. arg[] that contains at arg[0] the number of the rows of my cursor and at arg[1] String(0) of my cursor. Since one is integer and the other is string I have a problem. Any ideas how to fix this? public String[] getSubcategoriesRow(String id){ this.openDataBase(); String[] asColumnsToReturn = new String[] {SECOND_COLUMN_ID,SECOND_COLUMN_SUBCATEGORIES,}; Cursor cursor = this.dbSqlite.query(SECOND_TABLE_NAME, asColumnsToReturn, SECOND_COLUMN_SUBCATEGORIES + "= \"" + id + "\"", null, null, null, null); String string = cursor.getString(0); int count = cursor.getCount(); String arg[] = new String[]{count, string}; cursor.close(); return arg; } The cursor and the results and correct i just need to compine them to an array in order to return that.

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• Using temporary arrays to cut down on code - inefficient?

  - by tommaisey

  I'm new to c++ (and SO) so sorry if this is obvious. I've started using temporary arrays in my code to cut down on repetition and to make it easier to do the same thing to multiple objects. So instead of: MyObject obj1, obj2, obj3, obj4; obj1.doSomming(arg); obj2.doSomming(arg); obj3.doSomming(arg); obj4.doSomming(arg); I'm doing: MyObject obj1, obj2, obj3, obj4; MyObject* objs[] = {&obj1, &obj2, &obj3, &obj4}; for (int i = 0; i !=4; ++i) objs[i]->doSomming(arg); Is this detrimental to performance? Like, does it cause unnecessary memory allocation? Is it good practice? Thanks.

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• How can a Perl force its caller to return? [closed]

  - by JS Bangs

  Possible Duplicate: Is it possible for a Perl subroutine to force its caller to return? I want to write a subroutine which causes the caller to return under certain conditions. This is meant to be used as a shortcut for validating input to a function. What I have so far is: sub needs($$) { my ($condition, $message) = @_; if (not $condition) { print "$message\n"; # would like to return from the *parent* here } return $condition; } sub run_find { my $arg = shift @_; needs $arg, "arg required" or return; needs exists $lang{$arg}, "No such language: $arg" or return; # etc. } The advantage of returning from the caller in needs would then be to avoid having to write the repetitive or return inside run_find and similar functions.

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• Is this an example for parametric polymorphism?

  - by mrt181

  Hi i am educating myself oop principles. I would like to know if this is a correct example of Cardellis definition of parametric polymorphism. Please enlighten me. The example is in cfml's script based syntax. <cfcomponent> <cfscript> public numeric function getlength(any arg, string type){ switch (arguments.type){ case "array": return arraylen(arguments.arg); break; case "struct": return structcount(arguments.arg); break; case "string": return len(arguments.arg); break; case "numeric": return len(arguments.arg); break; case "object": // gets the number of parent classes, substracting the railo base class return -1 + arraylen(structfindkey(getmetadata(arguments.arg),"extends","all")); break; default: // throw was added to railo as a user defined function to use it in cfscript throw("InvalidTypeArgument","The provided type argument is invalid for method getlength"); } } </cfscript> </cfcomponent>

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• C++0x rvalue references and temporaries

  - by Doug

  (I asked a variation of this question on comp.std.c++ but didn't get an answer.) Why does the call to f(arg) in this code call the const ref overload of f? void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } My intuition says that the f(string &&) overload should be chosen, because arg needs to be converted to a temporary no matter what, and the temporary matches the rvalue reference better than the lvalue reference. This is not what happens in GCC and MSVC. In at least G++ and MSVC, any lvalue does not bind to an rvalue reference argument, even if there is an intermediate temporary created. Indeed, if the const ref overload isn't present, the compilers diagnose an error. However, writing f(arg + 0) or f(std::string(arg)) does choose the rvalue reference overload as you would expect. From my reading of the C++0x standard, it seems like the implicit conversion of a const char * to a string should be considered when considering if f(string &&) is viable, just as when passing a const lvalue ref arguments. Section 13.3 (overload resolution) doesn't differentiate between rvalue refs and const references in too many places. Also, it seems that the rule that prevents lvalues from binding to rvalue references (13.3.3.1.4/3) shouldn't apply if there's an intermediate temporary - after all, it's perfectly safe to move from the temporary. Is this: Me misreading/misunderstand the standard, where the implemented behavior is the intended behavior, and there's some good reason why my example should behave the way it does? A mistake that the compiler vendors have somehow all made? Or a mistake based on common implementation strategies? Or a mistake in e.g. GCC (where this lvalue/rvalue reference binding rule was first implemented), that was copied by other vendors? A defect in the standard, or an unintended consequence, or something that should be clarified?

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