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  • Why use Visual Studio 6 for C++

    - by robUK
    Hello, I am just wondering why programmers who program in C++ for windows always use Visual Studio 6 instead of Visual Studio 2008? Isn't the compiler in 2008 much better than the one in VS6? The reason I ask as I have used many sdk's that are always written in VS6? Many thanks, Steve

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  • Why does defined(X) not work in a preprocessor definition without a space?

    - by Devin
    A preprocessor definition that includes defined(X) will never evaluate to true, but (defined X) will. This occurs in MSVC9; I have not tested other preprocessors. A simple example: #define FEATURE0 1 #define FEATURE1 0 #define FEATURE2 1 #define FEATURE3 (FEATURE0 && !FEATURE1 && (defined(FEATURE2))) #define FEATURE4 (FEATURE0 && !FEATURE1 && (defined FEATURE2)) #define FEATURE5 (FEATURE0 && !FEATURE1 && (defined (FEATURE2))) #if FEATURE3 #pragma message("FEATURE3 Enabled") #elif (FEATURE0 && !FEATURE1 && (defined(FEATURE2))) #pragma message("FEATURE3 Enabled (Fallback)") #endif #if FEATURE4 #pragma message("FEATURE4 Enabled") #elif (FEATURE0 && !FEATURE1 && (defined FEATURE2)) #pragma message("FEATURE4 Enabled (Fallback)") #endif #if FEATURE5 #pragma message("FEATURE5 Enabled") #elif (FEATURE0 && !FEATURE1 && (defined (FEATURE2))) #pragma message("FEATURE5 Enabled (Fallback)") #endif The output from the compiler is: 1FEATURE3 Enabled (Fallback) 1FEATURE4 Enabled 1FEATURE5 Enabled Working cases: defined (X), defined( X ), and defined X. Broken case: defined(X) Why is defined evaluated differently when part of a definition, as in the #if cases in the example, compared to direct evaluation, as in the #elif cases in the example?

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  • Is there any way to get MSVC to pass structs arguments in registers on x64?

    - by Luke
    For a function with signature: struct Pair { void *v1, *v2 }; void f(Pair p); compiled on x64, I would like Pair's fields to be passed via register, as if the function was: void f(void *v1, void *v2); Compiling a test with gcc 4.2.1 for x86_64 on OSX 10.6, I can see this is exactly what happens by examining the disassembly. However, compiling with MSVC 2008 for x64 on Windows, the disassembly shows that Pair is passed on the stack. I understand that platform ABIs can prevent this optimization; does anyone know any MSVC-specific annotations, calling conventions, flags, or other hacks that can get this to work? Thank you!

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  • Mono on OS X Compatible with MSVC 2010 peers?

    - by Chris
    I'm to begin .NET development at work but have the option of using MonoDevelop/Mono on OS X instead of MSVC 2010 on Windows and would prefer it because of my familiarity with OS X. We are likely going to use a number of popular frameworks, such as NHibernate and Castle DI - my question to those of you familiar with .NET development and Mono: will I be at much of a disadvantage? Are there strong incompatibilities or, with some "paper cuts", the two systems are roughly compatible? Again, my colleagues will be using MSVC 2010 and we intend on working on the same codebases together. Thanks for any insight you can give to this .NET newbie. EDIT: I should note I'll primarily be doing development with MVC 2, which I understand does work with Mono, and will have some leeward in choosing frameworks, i.e. I can avoid highly incompatible frameworks.

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  • How can I switch off exception handling in MSVC?

    - by Tamara
    Does anybody know how to switch off exception handling option in MSVC? I tried to set the option 'Enable C++ exceptions' to 'NO' and I got warning: warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc I would like to switch off the exception handler, too, but I don't know how. In my application I basically need more speer than stability, therefore I chose switching off the exception handling. I do not have any try/catch blocks, but I do use STL. When I switch the option 'Enable C++ exceptions' to 'NO' is there any way how to get rid of those warnings?

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  • What does msvc 6 throw when an integer divide by zero occurs?

    - by EvilTeach
    I have been doing a bit of experimenting, and have discovered that an exception is being thrown, when an integer divide by zero occurs. #include <iostream> #include <stdexcept> using namespace std; int main ( void ) { try { int x = 3; int y = 0; int z = x / y; cout << "Didn't throw or signal" << endl; } catch (std::exception &e) { cout << "Caught exception " << e.what() << endl; } return 0; } Clearly it is not throwing a std::exception. What else might it be throwing?

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  • How to query a CGI based webserver from an app written in MFC (MSVC 2008) and process the result?

    - by shan23
    Hi, I am exploring the option of querying a web-page, which has a CGI script running on its end, with a search string (say in the form of http://sw.mycompany.com/~tools/cgi-bin/script.cgi?param1=value1&param2=value2&param3=value3 ), and displaying the result on my app (after due processing of course). My app is written in MFC C++ , and I must confess that I have never attempted anything related to network programming before. Is what I'm trying to do very infeasible ? If not, could anyone point me at the resources I need to look at in order to go about this ? Thanks !

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  • Is there an easy way to make `boost::ptr_vector` more debugger friendly in Visual Studio?

    - by Billy ONeal
    I'm considering using boost::ptr_container as a result of the responses from this question. My biggest problem with the library is that I cannot view the contents of the collection in the debugger, because the MSVC debugger doesn't recognize it, and therefore I cannot see the contents of the containers. (All the data gets stored as void * internally) I've heard MSVC has a feature called "debugger visualizers" which would allow the user to make the debugger smarter about these kinds of things, but I've never written anything like this, and I'm not hugely firmiliar with such things. For example, compare the behavior of boost::shared_ptr with MSVC's own std::tr1::shared_ptr. In the debugger (i.e. in the Watch window), the boost version shows up as a big mess of internal variables used for implementing the shared pointer, but the MSVC version shows up as a plain pointer to the object (and the shared_ptr's innards are hidden). How can I get started either using or implementing such a thing?

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  • What is so great about Visual Studio?

    - by Paperflyer
    In my admittedly somewhat short time as programmer, I have used many development environments on many platforms. Most notably, Eclipse/Linux, XCode/OSX, CLI/editor/Linux, VisualDSP/Blackfin/Windows and MSVC/Windows. (I used each one for several months) There are neat features in pretty much all of them. But somehow, I just can't find any in MSVC. Then again, so many people really seem to like it, so I am probably missing something here. So please tell me: What is so great about Visual Studio? Things I like: Refactoring tools in Eclipse Build error highlighting in XCode and Eclipse Edit-all-in-Scope in XCode Profiler in XCode Flexibility of Eclipse and CLI/editor Data plotting in VisualDSP Things I don't like Build error display in MSVC (not highlighted in code) Honestly, this is not meant to be a rant. Of course I am a Mac-head and biased as hell, but I have to use MSVC on the job, so I really want to like it.

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  • Which compiler option I should choose?

    - by Surjya Narayana Padhi
    Hi Geeks, I have to use the third party static library for my qt application to run on windows. The third party provides me a .lib and .h file for use. These libraries are compiled with MSVC compiler. My qt Creator is using MinGW compiler to compile my application. I copied the .h and .lib file to my qt project directory and then added those in .pro file as follows QT += core gui TARGET = MyTest TEMPLATE = app LIBS += C:\Qt\2010.05\qt\MyTest\newApi.lib SOURCES += main.cpp\ mainwindow.cpp HEADERS += mainwindow.h \ newApi.h FORMS += mainwindow.ui Now I am getting some runtime error like this - Starting C:\Qt\2010.05\qt\MyTest-build-desktop\debug\MyTest.exe... C:\Qt\2010.05\qt\MyTest-build-desktop\debug\MyTest.exe exited with code -1073741515 Can any body suggest is this runtime error is due to mismatch of compiler? (because of my .lib file I added is comipled in MSVC compiler and my qt app is compiled using MinGW compiler) If not what may be the reason? Am I missing anything in adding the .h and .lib file to my qt project? If my MinGW compiler will not support the .lib file generated in MSVC compiler what may be the work-arround? Can I create the .lib files in MinGW compiler? or this format is supported only by MSVC compiler only? Please suggest...

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  • How do .so files avoid problems associated with passing header-only templates like MS dll files have?

    - by Doug T.
    Based on the discussion around this question. I'd like to know how .so files/the ELF format/the gcc toolchain avoid problems passing classes defined purely in header files (like the std library). According to Jan in that answer, the dynamic linker/loader only picks one version of such a class to load if its defined in two .so files. So if two .so files have two definitions, perhaps with different compiler options/etc, the dynamic linker can pick one to use. Is this correct? How does this work with inlining? For example, MSVC inlines templates aggressively. This makes the solution I describe above untenable for dlls. Does Gcc never inline header-only templates like the std library as MSVC does? If so wouldn't that make the functionality of ELF described above ineffective in these cases?

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  • Software requirements for replicating a Windows application

    - by gpuguy
    I developed an application using Windows Form in C++ (IDE MSVC 2010). Some part of application also has MFC, and OpenCv. I want to send the application to my cleint for interim testing on his own machine. I have not developed any installer for the same, and so I will be sending him the.EXE file. I want that the client should not face any difficulty in replicating the experiment, and thus saves his time. Can somebody suggest me what all softwares(such as, MSVC, .NET Framework, Windows SDK etc) should already be installed on the client's machine for successfull testing of the application? Note: OS (Windows 7) and hardware is exactly same at both sides.

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  • How to debug manifest errors?

    - by Rryk
    I am creating an application that depends on third-party library, which in turn depends on MSVCP90D.dll (it was compiled with debug symbols). While starting the application it fails to start and provides an error message: I have found such library in C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\redist\Debug_NonRedist\amd64\Microsoft.VC90.DebugCRT and C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\redist\Debug_NonRedist\x86\Microsoft.VC90.DebugCRT. As you can see one of them is 64-bit, while the other is 32-bit. When I have placed 32-bit into the directory of the application the application silently crashes while loading (log from Visual Studio Output window is below). With the 32-bit one I get another error message: If I press Abort -- programs shuts down, Retry results in breaking into debug session for crt0msg.c file. This is system file and I have no idea how to debug it. If I press Ignore I get yet another error message: So the question is how to debug such errors? Please give me some links where I can read more about it or point me out what exactly I should do in such cases. I know this relates to manifest problems -- please give me a good resource where I can read about resources, since what I have found have confused me even more. This is log for 64-bit version of the MSVCP90D.dll library: 'chrome.exe': Loaded 'D:\Projects\Chromium\devenv\install\build-msvc-debug\chromium-xml3d-rtsg2\chrome.exe', Symbols loaded. 'chrome.exe': Loaded 'C:\Windows\SysWOW64\ntdll.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\kernel32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\KernelBase.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\user32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\gdi32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\lpk.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\usp10.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\msvcrt.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\advapi32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\sechost.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\rpcrt4.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\sspicli.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\cryptbase.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\shell32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\shlwapi.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\winmm.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\version.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\psapi.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\imm32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\msctf.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'D:\Projects\Chromium\devenv\install\build-msvc-debug\chromium-xml3d-rtsg2\chrome.dll', Symbols loaded. 'chrome.exe': Loaded 'C:\Windows\SysWOW64\ole32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\oleaut32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.windows.common-controls_6595b64144ccf1df_6.0.7600.16385_none_421189da2b7fabfc\comctl32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\oleacc.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\opengl32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\glu32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\ddraw.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\dciman32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\setupapi.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\cfgmgr32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\devobj.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\dwmapi.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'C:\Windows\SysWOW64\secur32.dll', Symbols loaded (source information stripped). 'chrome.exe': Loaded 'D:\Projects\Chromium\devenv\install\build-msvc-debug\rtsg2\bin\RTSG2.dll', Symbols loaded. 'chrome.exe': Unloaded 'D:\Projects\Chromium\devenv\install\build-msvc-debug\chromium-xml3d-rtsg2\chrome.dll' 'chrome.exe': Unloaded 'D:\Projects\Chromium\devenv\install\build-msvc-debug\rtsg2\bin\RTSG2.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\secur32.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\opengl32.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\ddraw.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\dwmapi.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\setupapi.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\devobj.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\cfgmgr32.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\dciman32.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\glu32.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\oleacc.dll' 'chrome.exe': Unloaded 'C:\Windows\winsxs\x86_microsoft.windows.common-controls_6595b64144ccf1df_6.0.7600.16385_none_421189da2b7fabfc\comctl32.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\oleaut32.dll' 'chrome.exe': Unloaded 'C:\Windows\SysWOW64\ole32.dll' 'chrome.exe': Loaded 'C:\Windows\SysWOW64\ole32.dll', Symbols loaded (source information stripped). The program '[1152] chrome.exe: Native' has exited with code 9 (0x9).

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  • huge C file debugging problem

    - by valdo
    Hello all. I have a source file in my project, which has more than 65,536 code lines (112,444 to be exact). I'm using an "sqlite amalgamation", which comes in a single huge source file. I'm using MSVC 2005. The problems arrives during debugging. Everything compiles and links ok. But then when I'm trying to step into a function with the debugger - it shows an incorrect code line. What's interesting is that the difference between the correct line number and the one the debugger shows is exactly 65536. This makes me suspect (almost be sure in) some unsigned short overflow. I also suspect that it's not a bug in the MSVC itself. Perhaps it's the limitation of the debug information format. That is, the debug information format used by MSVC stores the line numbers as 2-byte shorts. Is there anything can be done about this (apart from cutting the huge file into several smaller ones) ?

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  • Need help with BOOST_FOREACH/compiler bug

    - by Jacek Lawrynowicz
    I know that boost or compiler should be last to blame, but I can't see another explanation here. I'm using msvc 2008 SP1 and boost 1.43. In the following code snippet execution never leaves third BOOST_FOREACH loop typedef Graph<unsigned, unsigned>::VertexIterator Iter; Graph<unsigned, unsigned> g; g.createVertex(0x66); // works fine Iter it = g.getVertices().first, end = g.getVertices().second; for(; it != end; ++it) ; // fine std::pair<Iter, Iter> p = g.getVertices(); BOOST_FOREACH(unsigned handle, p) ; // fine unsigned vertex_count = 0; BOOST_FOREACH(unsigned handle, g.getVertices()) vertex_count++; // oops, infinite loop vertex_count = 0; BOOST_FOREACH(unsigned handle, g.getVertices()) vertex_count++; vertex_count = 0; BOOST_FOREACH(unsigned handle, g.getVertices()) vertex_count++; // ... last block repeated 7 times Iterator code: class Iterator : public boost::iterator_facade<Iterator, unsigned const, boost::bidirectional_traversal_tag> { public: Iterator() : list(NULL), handle(INVALID_ELEMENT_HANDLE) {} explicit Iterator(const VectorElementsList &list, unsigned handle = INVALID_ELEMENT_HANDLE) : list(&list), handle(handle) {} friend std::ostream& operator<<(std::ostream &s, const Iterator &it) { s << "[list: " << it.list <<", handle: " << it.handle << "]"; return s; } private: friend class boost::iterator_core_access; void increment() { handle = list->getNext(handle); } void decrement() { handle = list->getPrev(handle); } unsigned const& dereference() const { return handle; } bool equal(Iterator const& other) const { return handle == other.handle && list == other.list; } const VectorElementsList<T> *list; unsigned handle; }; Some ASM fun: vertex_count = 0; BOOST_FOREACH(unsigned handle, g.getVertices()) // initialization 013E1369 mov edi,dword ptr [___defaultmatherr+8 (13E5034h)] // end iterator handle: 0xFFFFFFFF 013E136F mov ebp,dword ptr [esp+0ACh] // begin iterator handle: 0x0 013E1376 lea esi,[esp+0A8h] // begin iterator list pointer 013E137D mov ebx,esi 013E137F nop // forever loop begin 013E1380 cmp ebp,edi 013E1382 jne main+238h (13E1388h) 013E1384 cmp ebx,esi 013E1386 je main+244h (13E1394h) 013E1388 lea eax,[esp+18h] 013E138C push eax // here iterator is incremented in ram 013E138D call boost::iterator_facade<detail::VectorElementsList<Graph<unsigned int,unsigned int>::VertexWrapper>::Iterator,unsigned int const ,boost::bidirectional_traversal_tag,unsigned int const &,int>::operator++ (13E18E0h) 013E1392 jmp main+230h (13E1380h) vertex_count++; // forever loop end It's easy to see that iterator handle is cached in EBP and it never gets incremented despite of a call to iterator operator++() function. I've replaced Itarator implmentation with one deriving from std::iterator and the issue persisted, so this is not iterator_facade fault. This problem exists only on msvc 2008 SP1 x86 and amd64 release builds. Debug builds on msvc 2008 and debug/release builds on msvc 2010 and gcc 4.4 (linux) works fine. Furthermore the BOOST_FOREACH block must be repeaded exacly 10 times. If it's repeaded 9 times, it's all OK. I guess that due to BOOST_FOREACH use of template trickery (const auto_any), compiler assumes that iterator handle is constant and never reads its real value again. I would be very happy to hear that my code is wrong, correct it and move on with BOOST_FOREACH, which I'm very found of (as opposed to BOOST_FOREVER :). May be related to: http://stackoverflow.com/questions/1275852/why-does-boost-foreach-not-work-sometimes-with-c-strings

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  • How to generate .sln/.vcproj using qmake

    - by stas
    Hi! I have main.cpp in c:\test folder and do the following: qmake -project qmake -tp vc test.pro The answer is: WARNING: Unable to generate output for: C:/test//Makefile.Debug [TEMPLATE vcapp] WARNING: Unable to generate output for: C:/test//Makefile.Release [TEMPLATE vcapp] But, I don't need make files. I need .vcproj! Environment: Windows XP Pro SP3, MSVC 7.1 and 8.0. Qt is installed in C:\Qt\2010.02 (LGPL version). Commands are run from Qt Command Prompt. What's wrong with it? How to generate .sln/.vcproj? May I generate them for MSVC 7.1 and 8.0?

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  • cmake missing separator error

    - by user198729
    D:\Works\c\cmake\build>cmake .. -- The C compiler identification is MSVC -- The CXX compiler identification is MSVC -- Check for CL compiler version -- Check for CL compiler version - 1500 -- Check if this is a free VC compiler -- Check if this is a free VC compiler - no -- Check for working C compiler: D:/Tools/Microsoft Visual Studio 9.0/VC/bin/cl.exe -- Check for working C compiler: D:/Tools/Microsoft Visual Studio 9.0/VC/bin/cl.exe -- works -- Detecting C compiler ABI info -- Detecting C compiler ABI info - done -- Check for working CXX compiler: D:/Tools/Microsoft Visual Studio 9.0/VC/bin/cl.exe -- Check for working CXX compiler: D:/Tools/Microsoft Visual Studio 9.0/VC/bin/cl.exe -- works -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - done -- Configuring done -- Generating done -- Build files have been written to: D:/Works/c/cmake/build D:\Works\c\cmake\build>make Makefile:28: *** missing separator. Stop. I saw many similar problems,but not with cmake,and their solution is to use tabs instead of spaces,but the makefile is generated by cmake,has anyone else met this problem?

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  • VC++ 2010 wants to link boost libararies i didn't even specify

    - by Philipp
    Hi there, I'm trying to build my application with MSVC 2010 instead of GCC. With GCC everything works fine. My app uses boost_system and boost_thread libraries. I built boost with VC2010 in "system" layout, that means the libraries are named just libboost_system.lib (and not libboost_system_compiler_threading_version_wtf_snafu.lib) The libs reside in C:\Boost\lib, the Makefile specifies LFLAGS = /NOLOGO /INCREMENTAL:NO /SUBSYSTEM:CONSOLE LIBS = /LIBPATH:C:/Boost/lib libboost_system.lib libboost_thread.lib Ws2_32.lib when invoking nmake it compiles, but when trying to link it quits with LINK : fatal error LNK1104: cannot open file 'libboost_date_time-vc100-mt-1_43.lib I mean seriously, WTF? I told it to link libboost_systen.lib and libboost_thread.lib how come it tries to link libboost_data_time and why does it assume I built the libs in "tagged" layout?? How can I stop MSVC trying to be smart and guess what I might have wanted to link? Thanks, Philipp

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  • C++0x rvalue references - lvalues-rvalue binding

    - by Doug
    This is a follow-on question to http://stackoverflow.com/questions/2748866/c0x-rvalue-references-and-temporaries In the previous question, I asked how this code should work: void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } It seems that the move overload should probably be called because of the implicit temporary, and this happens in GCC but not MSVC (or the EDG front-end used in MSVC's Intellisense). What about this code? void f(std::string &&); //NB: No const string & overload supplied void g1(const char * arg) { f(arg); } void g2(const std::string & arg) { f(arg); } It seems that, based on the answers to my previous question that function g1 is legal (and is accepted by GCC 4.3-4.5, but not by MSVC). However, GCC and MSVC both reject g2 because of clause 13.3.3.1.4/3, which prohibits lvalues from binding to rvalue ref arguments. I understand the rationale behind this - it is explained in N2831 "Fixing a safety problem with rvalue references". I also think that GCC is probably implementing this clause as intended by the authors of that paper, because the original patch to GCC was written by one of the authors (Doug Gregor). However, I don't this is quite intuitive. To me, (a) a const string & is conceptually closer to a string && than a const char *, and (b) the compiler could create a temporary string in g2, as if it were written like this: void g2(const std::string & arg) { f(std::string(arg)); } Indeed, sometimes the copy constructor is considered to be an implicit conversion operator. Syntactically, this is suggested by the form of a copy constructor, and the standard even mentions this specifically in clause 13.3.3.1.2/4, where the copy constructor for derived-base conversions is given a higher conversion rank than other implicit conversions: A conversion of an expression of class type to the same class type is given Exact Match rank, and a conversion of an expression of class type to a base class of that type is given Conversion rank, in spite of the fact that a copy/move constructor (i.e., a user-defined conversion function) is called for those cases. (I assume this is used when passing a derived class to a function like void h(Base), which takes a base class by value.) Motivation My motivation for asking this is something like the question asked in http://stackoverflow.com/questions/2696156/how-to-reduce-redundant-code-when-adding-new-c0x-rvalue-reference-operator-over ("How to reduce redundant code when adding new c++0x rvalue reference operator overloads"). If you have a function that accepts a number of potentially-moveable arguments, and would move them if it can (e.g. a factory function/constructor: Object create_object(string, vector<string>, string) or the like), and want to move or copy each argument as appropriate, you quickly start writing a lot of code. If the argument types are movable, then one could just write one version that accepts the arguments by value, as above. But if the arguments are (legacy) non-movable-but-swappable classes a la C++03, and you can't change them, then writing rvalue reference overloads is more efficient. So if lvalues did bind to rvalues via an implicit copy, then you could write just one overload like create_object(legacy_string &&, legacy_vector<legacy_string> &&, legacy_string &&) and it would more or less work like providing all the combinations of rvalue/lvalue reference overloads - actual arguments that were lvalues would get copied and then bound to the arguments, actual arguments that were rvalues would get directly bound. Questions My questions are then: Is this a valid interpretation of the standard? It seems that it's not the conventional or intended one, at any rate. Does it make intuitive sense? Is there a problem with this idea that I"m not seeing? It seems like you could get copies being quietly created when that's not exactly expected, but that's the status quo in places in C++03 anyway. Also, it would make some overloads viable when they're currently not, but I don't see it being a problem in practice. Is this a significant enough improvement that it would be worth making e.g. an experimental patch for GCC?

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  • Building a dll with .lib files

    - by Manish Shukla
    I have a C++ project which is build via bjam. With 'install' rule in Jamroot i am able to create statically linked libraries (.lib files) for my project. My question is, how i can build a load-time DLL (or run-time DLL is also fine) with these .lib files? More Info: I am building my project with bjam in windows using msvc. When i tried compiling my project under visual C++ 2008, it complied and linked just fine but when i used bjam with msvc for compilation, it started giving linking errors and showing dependency from other project folders. Why was this behavior via bjam but not shown in vc++ UI.

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  • Is allocating a dynamic array without specifying size well formed code?

    - by Als
    The following simple program snippet gives compilation errorswith gcc-4.3.4. Program: int main() { char *ptr = new char[10]; char *ptr1 = new char[]; return 0; } Compilation errors: prog.cpp: In function ‘int main()’: prog.cpp:4: error: expected primary-expression before ‘]’ token prog.cpp:3: warning: unused variable ‘ptr’ prog.cpp:4: warning: unused variable ‘ptr1’ But the same compiles cleanly with MSVC without any diagnostic message. So my question is: Does the Standard allow an new [] to be called without specifying the size? Or this a bug in MSVC? Can someone provide a reference from the standard which will conclusively say that the above code example is ill-formed or well-formed? I have had a look at: 5.3.4 New [expr.new] & 18.4.1.2 Array forms [lib.new.delete.array] but couldnt find any conclusive evidence about the behavior.

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