Re: [Openexr-devel] C++11, 'throw', etc.

[Richard Addison-Wood]

It seems that it would be fairly straight forward to define some preprocessor macros that allow the exception specifications to be spelled out in the appropriate ways based on the what __cplusplus is set to.

Thus, we can continue to support users of ilmbase according to their own C++ language standard needs.

Even though the recent VFX Reference Platform specifications have been specifying C++11 for a while (and C++14 for 2018), there may still be facilities using third party applications dating to before that.  And there would be use cases that are entirely independent of the VFX Reference Platform.

When updates to OpenEXR lead to files being written that cannot be read by older versions of OpenEXR, we would want to avoid making any unwarranted hindrances that would block downstream users from updating to the newer OpenEXR.

On 08/12/17 11:20, Nick Rasmussen wrote:

It seems reasonable to me as well.  Removing the dynamic exception specifications would’t even break compatibility with older compilers. 

-nick

On Thu, Aug 10, 2017 at 11:52 AM Piotr Stanczyk <address@hidden> wrote:

Sounds like a sensible plan to me. 

Anyone from ILM care to comment on this? Can you foresee any internal build issues?

Piotr

On Thu, Aug 10, 2017 at 11:40 AM Larry Gritz <address@hidden> wrote:

Any vendors that have bought into VFX Platform (Autodesk, Foundry, SESI) should in theory have been on C++11 since last year (and should be on board for C++14 for any products coming in 2018).

We're only talking about moving forward, so a stray downstream product stuck on C++03 can keep using OpenEXR <= 2.2.

I'll give it a couple days to see if there are objections before I do any of the actual work. But it will be cleaner and easier if we can just assume C++11 as a minimum.

-- lg

On Aug 10, 2017, at 11:12 AM, Piotr Stanczyk <address@hidden> wrote:

Are there any vendors for whom this would cause an issue? Else, I would vote for moving things forward 

On 10 August 2017 at 10:18, Larry Gritz <address@hidden> wrote:

Ugh, so it's worse than I thought.

I suppose I'm willing to fix and submit a patch to address this.

Do I need to put in the proper macros to make it compile on everything from C++03 through 17? Does anybody want to argue for continuing to maintain C++03 compatibility for future OpenEXR releases, or is it finally time (six years after the C++ standard and 2+ years after VFXPlatform) to raise the floor to C++11?

-- lg

On Aug 9, 2017, at 11:38 PM, Werner Benger <address@hidden> wrote:

It should be noted that dynamic expressions are actually forbidden in C++17, so OpenEXR does no longer compile with GCC 7.1 when std C++17 is enabled. The highest C++ version that can be used to compile it is C++14, where it's still just a warning, while in C++17 it's an error. It would be good to have OpenEXR at least compilable in C++17.  Major C++ libraries such as QT are using C++11 nowadays, so it seems pretty safe to go beyond C++03 for modern applications, a lot of things are indeed much easier.

    Werner


On 10.08.2017 00:20, Larry Gritz wrote:

In a test compile with gcc 7, I get lots of errors of the following ilk:

/home/travis/build/lgritz/openexr/IlmBase/Imath/ImathVec.h:228:34: warning: dynamic exception specifications are deprecated in C++11 [-Wdeprecated]
     const Vec2 & normalizeExc () throw (IEX_NAMESPACE::MathExc);
                                  ^~~~~

I can disable this particular warning, of course, but it's worth noting that the OpenEXR code base is not C++11 compliant. But in addition to using some C++03 idioms that are deprecated in C++11, perhaps more importantly, the code is not taking advantage of new features such as move semantics, constexpr, nothrow, and others. For the Imath classes especially, using some of these may actually confer a performance benefit.

I feel kind of bad pointing this out while not really having the time at the moment to code up and submit an actual patch myself, but I thought I'd at least open the topic and see where the community stands on the issue of how and when to upgrade to C++11 and if it's important for modern OpenEXR to continue to support C++03. For point of reference, the VFX Reference Platform [http://www.vfxplatform.com/] dictated C++11 for 2016 and 2017, and will be C++14 for 2018.

-- lg

--
Larry Gritz
address@hidden





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Dr. Werner Benger                Visualization Research
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