Unions, common-initial subsequence and UB

[Wilhelm Meier <wilhelm.meier@xxxxxxxx>]

Hi all,

this is more a general question instead of a g++ specific one:

the standard explicitly makes this exception: accessing an inactive 
union member is not UB if the members are structs with initial common 
sequence.

Is this also true in a constexpr context? I ask this because the chapter 
for constexpr expression does not mention this exception accessing an 
inactive memeber.

Thanks for hints,
 Wilhelm