[Bug c++/102119] New: ICE when accessing an uninitialised variable in a dynamic array of unions in a constexpr context.

[Bug c++/102119] New: ICE when accessing an uninitialised variable in a dynamic array of unions in a constexpr context.

[gcc_report_187375 at mailfence dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102119

            Bug ID: 102119
           Summary: ICE when accessing an uninitialised variable in a
                    dynamic array of unions in a constexpr context.
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc_report_187375 at mailfence dot com
  Target Milestone: ---

Source code:
======================================
union U {
    int value;
    constexpr U() noexcept { }
    constexpr ~U() noexcept { }
};

constexpr int z() {
    U* array = new U[5];
    int result = array[3].value;
    delete[] array;
    return result;
}

constexpr int zz = z();

int main() { }
======================================


Compilation output (compiled with: gcc -v -save-temps -std=c++20):
======================================
Using built-in specs.
COLLECT_GCC=/opt/compiler-explorer/gcc-11.2.0/bin/g++
Target: x86_64-linux-gnu
Configured with: ../gcc-11.2.0/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,ada,go,d --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=Compiler-Explorer-Build-gcc--binutils-2.36.1
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.2.0 (Compiler-Explorer-Build-gcc--binutils-2.36.1) 
COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-g' '-o' '/app/output.s'
'-masm=intel' '-S' '-v' '-save-temps' '-std=c++20' '-shared-libgcc'
'-mtune=generic' '-march=x86-64' '-dumpdir' '/app/'

/opt/compiler-explorer/gcc-11.2.0/bin/../libexec/gcc/x86_64-linux-gnu/11.2.0/cc1plus
-E -quiet -v -imultiarch x86_64-linux-gnu -iprefix
/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/x86_64-linux-gnu/11.2.0/
-D_GNU_SOURCE <source> -masm=intel -mtune=generic -march=x86-64 -std=c++20
-fdiagnostics-color=always -g -fworking-directory -fpch-preprocess -o
/app/output.ii
ignoring nonexistent directory
"/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../x86_64-linux-gnu/include"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../include/c++/11.2.0"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../include/c++/11.2.0/x86_64-linux-gnu"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../include/c++/11.2.0/backward"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11.2.0/include"
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11.2.0/include-fixed"
ignoring nonexistent directory
"/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../include/c++/11.2.0

/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../include/c++/11.2.0/x86_64-linux-gnu

/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/x86_64-linux-gnu/11.2.0/../../../../include/c++/11.2.0/backward

/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/x86_64-linux-gnu/11.2.0/include

/opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/x86_64-linux-gnu/11.2.0/include-fixed
 /usr/local/include
 /opt/compiler-explorer/gcc-11.2.0/bin/../lib/gcc/../../include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-g' '-o' '/app/output.s'
'-masm=intel' '-S' '-v' '-save-temps' '-std=c++20' '-shared-libgcc'
'-mtune=generic' '-march=x86-64' '-dumpdir' '/app/'

/opt/compiler-explorer/gcc-11.2.0/bin/../libexec/gcc/x86_64-linux-gnu/11.2.0/cc1plus
-fpreprocessed /app/output.ii -quiet -dumpdir /app/ -dumpbase output.cpp
-dumpbase-ext .cpp -masm=intel -mtune=generic -march=x86-64 -g -std=c++20
-version -fdiagnostics-color=always -o /app/output.s
GNU C++20 (Compiler-Explorer-Build-gcc--binutils-2.36.1) version 11.2.0
(x86_64-linux-gnu)
        compiled by GNU C version 7.5.0, GMP version 6.1.0, MPFR version 3.1.6,
MPC version 1.0.3, isl version isl-0.18-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C++20 (Compiler-Explorer-Build-gcc--binutils-2.36.1) version 11.2.0
(x86_64-linux-gnu)
        compiled by GNU C version 7.5.0, GMP version 6.1.0, MPFR version 3.1.6,
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: 04bf73fb6238a66ccbfea1df0fdb5d66
'
<source>:14: confused by earlier errors, bailing out
======================================