constexpr not compiling in VC2013

Question

This constexpr code does not compiled in Visual Studio 2013 version 12.0.21005.1 REL

Is there a newer Visual Studio compiler that works with constexpr?

#include <iostream>

constexpr int factorial(int n)
{
    return n <= 1 ? 1 : (n * factorial(n - 1));
}

int main(void)
{
    const int fact_three = factorial(3);
    std::cout << fact_three << std::endl;
    return 0;
}

output from compilation:

    1>------ Build started: Project: Project1, Configuration: Debug Win32 ------
    1>  Source.cpp
    1>....\source.cpp(3): error C2144: syntax error : 'int' should be preceded by ';'
    1>....\source.cpp(3): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Herb Sutter mentions constexpr on his blog but is unclear in what version it works / will work? http://herbsutter.com/2013/09/09/visual-studio-2013-rc-is-now-available/#comment-13521

Solution 1

Microsoft publishes a C++11 compatibility table, under which constexpr is clearly marked as not being available in Visual Studio 2013.

The November 2013 CTP has it, though.

_{Source: Google visual studio constexpr}

Solution 2

constexpr is not supported in Visual Studio 2013 RTM, see the compatibility table. This is not only true for the RTM version, but also for the Visual Studio Updates.

If you want to stick to Visual Studio 2013, you could download the Visual C++ Compiler November 2013 CTP which comes with some new features, see MSDN blog. Unfortunately Microsoft has no merger with the latest Visual Studio Update features and the CTP features and clearly states that they don't plan to do so.

If we want it all, we need to wait for Visual Studio 2015, see the MSDN blog about VS 2015 Preview.

Solution 3

As is mentioned by the others, November 2013 Customer Technology Preview(CTP) will give you access to constexpr*

Note that just downloading the you'll need to change your "Platform Toolset" to "Visual C++ Compiler Nov 2013 CTP (CTP_Nov2013)" to use the new compiler. You can do that by opening your project's "Property Pages" And going to: "Configuration Properties" > "General" and then changing the "Platform Toolset".

*There is a bit of conflicting information on what portion of constexpr you actually have access to, but it's definitely not all of the standards definition of constexpr. Microsoft says here that the November 2013 CTP adds:

constexpr support (except for constructors)

Microsoft say here that it contains:

constexpr (except for member functions)

I can't even test if it has support for member functions, cause it definitely doesn't have support for any type of constexpr construction. For example this code gives this error with the November 2013 CTP:

error C2127: illegal initialization of 'constexpr' entity with a non-constant expression

One additional note: At time of writing the Visual Studio 2015 Preview still does not support constexpr construction. Keeping my fingers crossed on the final release.

Solution 4

You need to install VS2013 Update 5. (I was on Update 3 and it was not working) The thing about "Nov 2013 CTP" was inapplicable, as of this writing. You can do so by going here: https://my.visualstudio.com

and going to download, or : https://my.visualstudio.com/Downloads?q=visual%20studio%202013

View more solutions

Comments

[Jesse Good]

You need to get 2013 CTP, although note its still not complete (not yet implemented for member functions)).

[RichardPlunkett]

compiled and ran fine on gcc version 4.8.2 (GCC) for cygwin, with --std=c++11

[Damian]

Yes 2013 CTP works like a charm! ;-)

[Lightness Races in Orbit]

Interesting...

[Ray]

What does the CTP stand for?

[Jonathan Mee]

@Ray "Customer Technology Preview"

[blfuentes]

I have VS 2k13 Update 3 but not this compiler. I had to install it. Do you know if they will release it with newer updates or we have to wait until vs14?

[Lightness Races in Orbit]

@blacai: I don't know. Why not try the November 2013 CTP?

[blfuentes]

That is what I did. But I was checking if it was planned to update the compiler in a major update. The nov13 ctp was released last year and vs2k13 got several updates in 2014

[Lightness Races in Orbit]

@blacai: Can't help you there. The compatibility table says it's still unsupported and MS aren't great at documentation.

[Jean Davy]

"it's still unsupported" in this CTP, check comment from 'Lightness Races in Orbit' above ...

[Werner Henze]

@Jean Davy: Sorry, but this is nonsense. I just compiled the code from the question with the linked CTP.

[ildjarn]

If you're going to update your answer, you should take out any references/links to the CTP now that the VS2015 preview is available.

[Werner Henze]

@ildjarn The MS Download page says "VS2015 Preview is not intended for production use." I did not see such a statement for the November CTP download.

[ildjarn]

@WernerHenze : All MSFT CTPs (previews ;-]) have such wording.

[rubenvb]

@Werner "This is a Customer Technology Preview and does not come with a "Go Live" license." Sounds like its not recommended for production use either. The name kinda says it all, no?

[TankorSmash]

So the CTP is a preview, so it means it's not truly supported, and we shouldn't be rushing to use it. Treat it more like an experimental release is what I'm asking? Nevermind, down below there's a link saying not to use it in production.

[Lightness Races in Orbit]

@TankorSmash: Bear in mind that was two years ago. We have proper Visual Studio 2015 now, which the same linked table marks as having constexpr support.

[Emil Styrke]

VS2013 Update 5 does not include support for constexpr, as far as I can tell (I get a syntax error when compiling).