I am writing a managed DLL in VC2010 (i.e. /CLR is enabled for a VC++ DLL project). Following code wouldn't compile:
System::Collections::Generic::List<int>^ my_list;
for each(auto elem in my_list)
{
}
It raises error C3539: 'auto': a template-argument cannot be a type that contains 'auto'.
I don't understand the reason. I tried compiling the same in VS2012, and it raises same error (which is not appropriate error).
Why compiler fails to deduce the type for a colleciton? The same type of code would work in C# with var keyword.
First, the most importand point from the comments:
presented code does compile in VS2013 c++/cli dll .net 4.5 (Zee, 2014-05-03)
When you compile C++/CLI, which is the .NET binding for C++, you are using a different feature set of the Microsoft compiler. Whether something works either
when /clr is in effect
or, additionally, when you're using a "managed" construct (as in your code)
has nothing to to with if the "normal", native, MSVC compiler accepts it.
So as for "why": It would simply appear that auto type deduction did not work for the managed handle types in VS2010 and VS2012, but, according to Zee's comment, has then been implemented in VS2013. (A quick Search Engine check didn't find any official statement wrt. this, so I may be wrong.)
Related
The MS docs (even back in 2005) state for both:
_MANAGED : Defined to be 1 when /clr is specified.
__cplusplus_cli: Defined when compiling with /clr, /clr:pure, or /clr:safe. (...)
So if I'm compiling a C++/CLI module and need to check, which one should I use?
The answer is mentioned here:
both macros are supposed to be defined if the /clr option is
specified. Are you perchance using /clr:oldSyntax? In that case,
you're targeting Managed C++, not C++/CLI
And indeed, when looking at the 2003 docs there is only _MANAGED and there is no C++/CLI there yet.
To answer which one should I use, I'd say it doesn't really matter unless you need to differentiate between oldSyntax and CLI.
dllmain.cpp(16): warning C4447: 'main' signature found without threading mode
l. Consider using 'int main(Platform::Array<Platform::String^>^ args)'.
Above is a warning I got from building a Windows Store App DLL project. I didn't change anything in that default dllmain.cpp file except for including my own version of pch.
The documentation for this warning (along with many VS2012 errors/warnings) is nowhere to be found on MSDN and here is the only relevant link I can find:
http://social.msdn.microsoft.com/Forums/en-US/vssetup/thread/6daa9587-fe54-4e84-a8b9-0e5c52c2f6e8/
and the op there didn't get an answer.
If anyone knows what it means and how to fix it, it would be great!
As far as I can tell, you can safely ignore the warning. The compiler cribs when it sees a Win32-style DllMain being compiled using the /ZW flag (Consume Windows Runtime Extensions). However, the function gets called as you'd normally expect.
Alternatively, you can work around the warning by compiling dllmain.cpp without /ZW. You might need to adjust the PCH settings for this to properly work. This is the path taken by the DLL (Windows Store apps) C++/CX project template in Visual Studio.
Incidentally, the reason you do not get the warning when you're trying to build a Windows Runtime Component project (which builds everything using /ZW) is that a Windows Runtime Component doesn't declare a DllMain. This is not to say that it can't; it just picks up the dummy DllMain that the CRT defines (which basically turns off per-thread initialization and reports success).
I have a new project where I cannot use boost::format. I get a compiler error complaining that boost's override of a virtual function, ~basic_altstringbuf, lacks a "throw()". Even the most trivial attempt to use boost::format does that.
I have other projects where it works fine. I have verified that the new project uses the same include-paths for boost, and for the VC++ includes. All the projects have "Enable C++ Exceptions" set to Yes. The only explanation I can come up with is that the projects that work have some #DEFINE or some setting that disables those vile exception specs in the std:: include-files. But I have no idea what or where it might be. Any ideas?
Error 1 error C2694: 'boost::io::basic_altstringbuf::~basic_altstringbuf(void)': overriding virtual function has less restrictive exception specification than base class virtual member function 'std::basic_streambuf<_Elem,_Traits>::~basic_streambuf(void) throw()
EDIT: Corollary question: Is there a Properties-item in VS++ 2012 that will cause the std:: header files to be included without exception-specs? - short of turning off exceptions, that is?
At the request of the original owner of the green check-mark, I am submitting this summary.
The bugs are on the Microsoft side, in header-files for C++ standard library interfaces, and in the VC++ compiler when "Disable Language Extensions" is NOT set. The header files contain exception-specifications that the standard does not call for. When "language extensions" are not enabled, the compiler accepts invalid code. I have filed a bug report.
Boost could work around the problem in this specific case by adding seven characters to a nested include-file, i.e. "throw()" at line 65 in alt_sstream_impl.hpp. I filed a report with boost also, although I made it clear that the bug is not in their code. I am just suggesting a workaround.
All the tedious details are in the two reports linked above.
Check the preprocessor defines.
You might turn on and inspect verbose logging to see the exact flags that are passed to cl.exe
You could keep the preprocessed source and compare the version from the old (working) project with the new (failing) project.
My gut says, something else is being #defined/passed using -D in the old project that is not being defined in the new project, of differently (think of WINVER type macros)
See new answer posted: VC++ 2012 and Boost incompatibility - `throw()` specifications in library headers
EDIT by OP, Jive Dadson - It turned out to be /Za, which enables/disables "Microsoft language extensions." It is the contention of Visual Studio that the C++ standard requires that a program shall not compile if it has a virtual function override that is less restrictive in the "throw()" category than the function it overrides. Boost has a class that derives from basic_streambuf, and has a virtual destructor that lacks "throw()". The original destructor has that evil festoon. My new project will compile boost::format if I turn MS language extensions ON.
So the question becomes, who is wrong, and how? Is it standard-complying to put throw() on that destructor or not? Is the desired behavior (desired by me, that is) actually an "extension"? I seem to recall that MS considered some standard C++11 features to be "extensions," but I am not sure I remember correctly. Anyway, I will leave it to the boosters to decide, if they are interested. https://svn.boost.org/trac/boost/ticket/7477
By default, Visual Studio compiles a project to use the Multi Threaded DLL, found in the Visual Studio runtime. I want to compile my program using only /MT instead of /MD. Granted, that most systems already have this installed, and it's also available as a re-distributable.
When I change /MD to /MT, I get an error:
MSVCRTD.lib(MSVCR100D.dll) : error LNK2005: _free already defined in LIBCMT.lib(free.obj)
And four or five similar errors.
To try and fix this I removed LIBCMT.LIB from the default libraries.
I then get the error:
libcpmt.lib(_tolower.obj) : error LNK2019: unresolved external symbol __calloc_crt referenced in function __Getctype
Removing MSVCRTD.lib from the default list leads to similar errors?
It should be noted that:
-This is an OpenGL project, using the glfw library.
-I am using the SOIL image library by lonesock for texture loading.
Without any further precise information, I would say your first problem is that you're somehow mixing release and debug versions of libraries. MSVCRTD.lib is the debug version of MSVCRT.lib.
Either you have some debug settings hanging around in your own projects, or you're linking against debug versions of libraries you're using.
Never ever mix debug and release versions. If you're lucky you get an error like this. In some rare situations all magically seems to work until it doesn't.
I am trying to build an old version of an application which consists of VC++ projects that were written in Visual Studio 2003.
My OS is Windows 7 Enterprise (64-bit).
When I try and build the solution I get the following errors:
error C4772: #import referenced a type from a missing type library; '__missing_type__' used as a placeholder
fatal error C1084: Cannot read type library file: 'Smegui.tlb': Error loading type library/DLL.
They both complain about the following import statement:
#import "Smegui.tlb" no_implementation
This is not a case of the file path being incorrect as renaming the Smegui.tlb file causes the compiler to throw another error saying it cannot find the library.
Smegui is from another application that this one depends on. I thought perhaps I was missing a dll but there is no such thing as Smegui.dll.
All I know about .tlb files is that they are a type library and you can create them from an assembly using tlbexp.exe or regasm.exe (the later also registers the assembly with COM)
There is also an Apache Ant build script which uses a custom task to invoke devenv.com to build the projects. This is the same script that the build server originally used to build the application. It gives me the same errors when I try and run it.
The strangest thing about this is that I knew it ought to work seeing as it is all freshly checked out from subversion. I tried many different combinations of admin vs user elevation, VS vs Ant build, cleaning, release.
I have got it to build successfully about 5 times but the build seems to be non-deterministic.
If anyone can shed some light on how this tlb stuff even works or what this error might mean I would greatly appreciate it.
I found a far more reliable solution: open the tlb with oleview.exe and then close it.
Not sure what this actually does but it works every time.
I think oleview is actually one of the samples included with Visual Studio but I haven't had the time to debug it and see what it is doing.
I ran into this error because one type library was trying to load a dependent type library, which it could not find. Even though the dependent type library was in the same directory, and even though that directory was in the searchable path, the compiler would error loading the first type library, but not mention the dependent type library in the error.
To find the pseudo-missing type library, I ran Process Monitor (procman64.exe) during the compile. This showed that after the reported type library had successfully loaded, a dependent type library could not be found. It even showed all of the places that it was looking for the dependent type library, none of which were where it should have been looking (e.g.: ).
The fix was to add a <PreBuildEvent> to the project to copy the dependent .tlb file to one of the directories that was actually being searched.
<PreBuildEvent>
<Command>copy /Y ..\Lib\Interop\CWSpeechRecLib.tlb .\</Command>
</PreBuildEvent>
http://msdn.microsoft.com/en-us/library/sce74ah7%28VS.71%29.aspx
smegui.tlb is referencing some other tlb that the compiler can't find. If you have the .idl for smegui you might be able to figure out what the other is. I suspect the missing tlb is something that original build machine had registered but that your machine doesn't have registered.
A type library is a binary description of a set of interfaces, coclasses and enums. They're usually generated for COM components, in the case of tlbexp and regasm the tlb is created from the assembly metadata. For native COM components they are usually generated from an idl (Interface Description Language) file by the midl tool.
Edit:
I just noticed you're on x64 Windows. Are you building the project with a new version of Visual Studio? If so, are you targeting x86 or x64? If the latter, it may simply be a 32bit component that the compiler can't find (or less likely, a x64 component the x86 compiler can't find if you are targeting x86), for WOW64 the registry is virtualized for x86 vs. x64 applications.
Well I finally found out why I managed to get it to build sometimes and not others... sort of.
So long as I ran the build script with elevated administrator permissions and let that get as far as it could until that error occurred, then run the build script again as a protected administrator succeeded. Those steps must be done in that exact order with no other steps in between. If I try build in Visual Studio it does not work (although I did get it to succeed once). Probably some kind of virtualisation issue although it still doesn't quite make sense.
Well I don't need help on this any more and I know it's probably impossible to fully answer this question without knowing exactly what the build is doing. However if anyone does have any more thoughts I would happily receive them.
Cheers,
Steiny