[LLVMdev] [RFC] Raising minimum required Visual Studio version to 2013 for trunk

[Michael Spencer]

On Mon, Aug 25, 2014 at 12:04 PM, Gao, Yunzhong
<yunzhong_gao at playstation.sony.com> wrote:
> Hi,
> Sorry for the delay in responding, we have been discussing this internally
> and have not had time to do a proper investigation.
>
>> We absolutely have to ship a set of DLLs that run hosted in VS2012. Is
>> there any sort of runtime incompatibility that would happen if we
>> built with 2013, needed the 2013 CRT, but tried to run inside the
>> VS2012 process? That would be a complete show stopper for us since we
>> have a committed schedule for support of versions of VS that we host in.
>
>> Has any size/performance testing been done to compare LLVM built with
>> the two versions of MSVC? Perf regressions are bad, m'kay?
>
> I do not know the answer to either of Alex's questions, so I am a bit
> concerned. Two weeks is not going to be enough to test the updates; two
> months might be more realistic...
>
> What is the impact on the static libraries (such as LLVMCore.lib or
> ClangLex.lib)? Can libraries built with Visual Studio 2013 link with other
> objects built with Visual Studio 2012 or earlier?
>
> - Gao

No, you cannot link C++ code compiled with one version of VS to C++
code compiled with a different version of VS. The C++ ABI and standard
library change between versions.

- Michael Spencer

>
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Aaron Ballman
> Sent: Friday, August 22, 2014 6:01 AM
> To: Renato Golin
> Cc: LLVM Developers Mailing List
> Subject: Re: [LLVMdev] [RFC] Raising minimum required Visual Studio version to 2013 for trunk
>
> On Fri, Aug 22, 2014 at 8:58 AM, Renato Golin <renato.golin at linaro.org> wrote:
>> On 22 August 2014 13:43, Aaron Ballman <aaron at aaronballman.com> wrote:
>>> My opposition to this switch was the timing. When we researched "what
>>> minimum can we live with for C++11" nine months ago, we determined
>>> what versions would make sense, which included MSVC 2012, and told
>>> people what the plan was. My concern was pulling the rug out from
>>> under people who were relying on that determination without putting
>>> in the proper research and giving them enough time to react.
>>
>> The fact that you spoke, and others echoed your views, is proof that
>> what you fear will not happen.
>>
>> Chandler's plan is simply showing the failures before we switch, which
>> is exactly what we've done last time, what you're asking now, and what
>> we'll do next.
>>
>> Progress is made by breaking small things, one at a time. :)
>
> We're in violent agreement. :-)
>
> ~Aaron
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