[Bug c++/85723] New: [C++17][DR 1496] __is_trivial intrinsic fails with no trivial non-deleted default c'tor

[joseph_marino at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85723

            Bug ID: 85723
           Summary: [C++17][DR 1496] __is_trivial intrinsic fails with no
                    trivial non-deleted default c'tor
           Product: gcc
           Version: 8.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joseph_marino at hotmail dot com
  Target Milestone: ---

gcc version 8.1.0 (GCC-Explorer-Build) when compiled with the flags:

-std=c++17 -Wall -Wextra

rejects the following code:

struct NonTrivial { NonTrivial() = delete; };
static_assert(!__is_trivial (NonTrivial), "NonTrivial is trivial");

emitting:

<source>:2:15: error: static assertion failed: NonTrivial is trivial


The assert should pass, as all default constructors of NonTrivial are deleted,
which does not meet the requirements in 12 [class] p6:

A trivial class is a class that is trivially copyable and has one or more
default constructors (15.1), all of which are either trivial or deleted and
**at least one of which is not deleted**.

This wording was introduced by the acceptance of DR 1496.


Full contents of compiling with -v follow:

Using built-in specs.

COLLECT_GCC=/opt/compiler-explorer/gcc-8.1.0/bin/g++

Target: x86_64-linux-gnu

Configured with: ../gcc-8.1.0/configure
--prefix=/opt/compiler-explorer/gcc-build/staging --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu --disable-bootstrap
--enable-multiarch --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --enable-clocale=gnu --enable-languages=c,c++,fortran
--enable-ld=yes --enable-gold=yes --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-linker-build-id --enable-lto
--enable-plugins --enable-threads=posix --with-pkgversion=GCC-Explorer-Build

Thread model: posix

gcc version 8.1.0 (GCC-Explorer-Build) 

COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-g' '-o'
'/tmp/compiler-explorer-compiler11849-52-1aa40zw.lzvg/output.s' '-masm=intel'
'-S' '-v' '-std=c++17' '-Wall' '-Wextra' '-shared-libgcc' '-mtune=generic'
'-march=x86-64'


/opt/compiler-explorer/gcc-8.1.0/bin/../libexec/gcc/x86_64-linux-gnu/8.1.0/cc1plus
-quiet -v -imultiarch x86_64-linux-gnu -iprefix
/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/x86_64-linux-gnu/8.1.0/
-D_GNU_SOURCE <source> -quiet -dumpbase example.cpp -masm=intel -mtune=generic
-march=x86-64 -auxbase-strip
/tmp/compiler-explorer-compiler11849-52-1aa40zw.lzvg/output.s -g -Wall -Wextra
-std=c++17 -version -fdiagnostics-color=always -o
/tmp/compiler-explorer-compiler11849-52-1aa40zw.lzvg/output.s

GNU C++17 (GCC-Explorer-Build) version 8.1.0 (x86_64-linux-gnu)

        compiled by GNU C version 5.4.0 20160609, GMP version 6.1.0, MPFR
version 3.1.4, MPC version 1.0.3, isl version isl-0.18-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072

ignoring nonexistent directory
"/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../x86_64-linux-gnu/include"

ignoring duplicate directory
"/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../include/c++/8.1.0"

ignoring duplicate directory
"/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../include/c++/8.1.0/x86_64-linux-gnu"

ignoring duplicate directory
"/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../include/c++/8.1.0/backward"

ignoring duplicate directory
"/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/8.1.0/include"

ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"

ignoring duplicate directory
"/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/8.1.0/include-fixed"

ignoring nonexistent directory
"/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../x86_64-linux-gnu/include"

ignoring duplicate directory "/usr/include/x86_64-linux-gnu"

#include "..." search starts here:

#include <...> search starts here:

 /usr/include/x86_64-linux-gnu


/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../include/c++/8.1.0


/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../include/c++/8.1.0/x86_64-linux-gnu


/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/x86_64-linux-gnu/8.1.0/../../../../include/c++/8.1.0/backward

 /opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/x86_64-linux-gnu/8.1.0/include


/opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/x86_64-linux-gnu/8.1.0/include-fixed

 /usr/local/include

 /opt/compiler-explorer/gcc-8.1.0/bin/../lib/gcc/../../include

 /usr/include

End of search list.

GNU C++17 (GCC-Explorer-Build) version 8.1.0 (x86_64-linux-gnu)

        compiled by GNU C version 5.4.0 20160609, GMP version 6.1.0, MPFR
version 3.1.4, MPC version 1.0.3, isl version isl-0.18-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072

Compiler executable checksum: 2a4ed8141a9e6ff21b9c06e24d4e4c1a

<source>:2:15: error: static assertion failed: NonTrivial is trivial

 static_assert(!__is_trivial (NonTrivial), "NonTrivial is trivial");

               ^~~~~~~~~~~~~~~~~~~~~~~~~~

Compiler returned: 1