Hi Ben,
That is not correct. Your suggestion would fix C++11 compilation on Linux and
Windows. However,
it would still break on C++ on Windows. static_assert is a keyword on Windows
on both C++ and C++11.
However, this isn’t the case on Linux. It’s present only in C++11.
What is the inclination to use static_assert inside expressions on C++? Since
this is an edge-case, I feel that
we should isolate this behavior instead of letting it permeate. In future, if
this is supported, it would be easier to fix this single nuance.
Eg:
Something like this:
#define BUILD_ASSERT_IN_EXPR(EXPR) []{static_assert(EXPR, "assertion failed”);}
Thanks,
Sairam
On 12/20/17, 8:18 AM, "Ben Pfaff" <[email protected]> wrote:
>I don't know what you mean by "all existing definitions". BUILD_ASSERT
>has a few definitions but only one of them matters in this case:
>
> #elif defined(__cplusplus) && __cplusplus >= 201103L
> #define BUILD_ASSERT(EXPR) static_assert(EXPR, "assertion failed")
>
>The post you cite implies that adding []{...} to the definition above
>would fix the problem. Is that correct?
>
>On Wed, Dec 20, 2017 at 12:45:04AM +0000, Sairam Venugopal wrote:
>> Hi Ben,
>>
>> I did consider updating the definition of BUILD_ASSERT, however, that would
>> involve changing all existing definitions (even non-expression context).
>> This issue is prevalent on both Linux and Windows when we start compiling in
>> C++ 11.
>>
>> Associated post:
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_31311748_is-2Dthere-2Dany-2Dway-2Dto-2Dslip-2Da-2Dstatic-2Dassert-2Dinto-2Dan-2Dexpression-2Din-2Diso-2Dc11&d=DwIBAg&c=uilaK90D4TOVoH58JNXRgQ&r=Z6vowHUOjP5ysP_g372c49Nqc1vEKqHKNBkR5Q5Z7uo&m=w5lx09Yyfn1993a2Tdgq4IXnaFsMjRcYiRSRftu2nek&s=6YRaA_irydpTc7N1-EXIctKiFclTsRSrh9XFKKRbQlA&e=
>>
>> The ideal fix would be to not use static_assert as an expression in C++11
>> mode.
>> Currently, we hit this issue here :
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_openvswitch_ovs_blob_master_lib_unaligned.h-23L172&d=DwIBAg&c=uilaK90D4TOVoH58JNXRgQ&r=Z6vowHUOjP5ysP_g372c49Nqc1vEKqHKNBkR5Q5Z7uo&m=w5lx09Yyfn1993a2Tdgq4IXnaFsMjRcYiRSRftu2nek&s=X99J8FVdp3jAiS3mMS4DWKMbIJgphnTA5fptRDK_BXU&e=
>>
>> You can disregard this patch for the time being since we will need to fix
>> this on both Linux and Windows.
>>
>> Thanks,
>> Sairam
>>
>>
>>
>> On 12/19/17, 3:45 PM, "Ben Pfaff" <[email protected]> wrote:
>>
>> >On Tue, Dec 19, 2017 at 03:32:27PM -0800, Sairam Venugopal wrote:
>> >> A static assert declaration may appear at block scope (as a block
>> >> declaration) and inside a class body (as a member declaration). However,
>> >> unlike sizeof, static_assert cannot be used as an expression and this is
>> >> strictly enforced on MSVC. error C2059: syntax error : static_assert
>> >>
>> >> Signed-off-by: Sairam Venugopal <[email protected]>
>> >
>> >I'd really prefer to adjust the definition of BUILD_ASSERT so that it
>> >can be used in any expression context. Did you consider that?
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