[Bug c++/70552] __builtin_constant_p fails to reflect the constness of constexpr calls

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70552

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-04-15
     Ever confirmed|0                           |1

--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
I'm going to confirm this report on the basis of others similar to it, such as
bug 19449 which has some interesting background.  The patch referenced from it
sets a precedent for the intrinsic treating constant expressions as constant
despite its late evaluation under "normal" circumstances (the
force_folding_builtin_constant_p global variable was put in place to circumvent
this delayed evaluation).  cxx_eval_builtin_function_call() in cp/constexpr.c
does set force_folding_builtin_constant_p to true, making it clear that the
intent is for the intrinsic to be evaluated during constexpr evaluation in C++.
 Something seems to be interfering with it (I just haven't yet figured out
what).