Created attachment 52060 [details]
reduced testcase

Compiler output:
$ x86_64-pc-linux-gnu-gcc -O2 -fno-guess-branch-probability -fharden-conditional-branches -fno-sched-critical-path-heuristic -fno-peephole2 -fsched2-use-superblocks testcase.C 
testcase.C: In member function 'virtual void C::_ZThn8_N1C3fooEi(int)':
testcase.C:15:16: error: qsort comparator non-negative on sorted output: 1
   15 |   virtual void foo (int);
      |                ^~~
during RTL pass: sched2
testcase.C:15:16: internal compiler error: qsort checking failed
0xdd17db qsort_chk_error
        /repo/gcc-trunk/gcc/vec.c:204
0xdd18ed qsort_chk(void*, unsigned long, unsigned long, int (*)(void const*, void const*, void*), void*)
        /repo/gcc-trunk/gcc/vec.c:246
0x27f18d5 gcc_qsort(void*, unsigned long, unsigned long, int (*)(void const*, void const*))
        /repo/gcc-trunk/gcc/sort.cc:270
0x2605888 ready_sort_real
        /repo/gcc-trunk/gcc/haifa-sched.c:3095
0x260dfb4 ready_sort
        /repo/gcc-trunk/gcc/haifa-sched.c:3111
0x260dfb4 schedule_block(basic_block_def**, void*)
        /repo/gcc-trunk/gcc/haifa-sched.c:6718
0x26e5f1b schedule_ebb(rtx_insn*, rtx_insn*, bool)
        /repo/gcc-trunk/gcc/sched-ebb.c:536
0x26e6642 schedule_ebbs()
        /repo/gcc-trunk/gcc/sched-ebb.c:655
0x15faf6c rest_of_handle_sched2
        /repo/gcc-trunk/gcc/sched-rgn.c:3740
0x15faf6c execute
        /repo/gcc-trunk/gcc/sched-rgn.c:3878
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r12-6113-20211224170936-g8f921393e33-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++ --enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra --disable-bootstrap --with-cloog --with-ppl --with-isl --build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld --with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch --prefix=/repo/gcc-trunk//binary-trunk-r12-6113-20211224170936-g8f921393e33-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20211224 (experimental) (GCC)