powerpc64 head -r345044: WITH_LLVM_LIBUNWIND= based buildworld leads to thrown C++ exceptions segmentation faulting

[I sometimes experiment with building powerpc64 (and 32-bit) via
more modern toolchains, here a amd64->powerpc64 cross build via
system-clang (so 8.0.0).]

buildworld with WITH_LLVM_LIBUNWIND= completes for powerpc64
(but not 32-bit powerpc). However, for a system installed
from such for pwoerpc64, the following program (for example)
gets a segmentation fault:

# more ~/c_tests/exception_test.cpp 
#include <exception>

int main(void)
{
    try { throw std::exception(); }
    catch (std::exception& e) {}
    return 0;
}

(Note: the same a.out works under a WITHOUT_LLVM_LIBUNWIND=
environment, that was patched for DW_CFA_remember_state and
DW_CFA_restore_state handling, with the system built via
devel/powerpc64-xtoolchain-gcc related materials. So the
failure is on the system library does of things for the
WITH_LLVM_LIBUNWIND= context.)

Unfortunately:

A) devel/gdb makes extensive use of thrown C++ exceptions
   and so does not work for a powerpc64 system based on
   WITH_LLVM_LIBUNWIND= .

B) The world built is not using dwarf-2 so /usr/libexec/gdb
   is not handy/useful.

C) CFLAGS+=-gdwarf-2 leads to system-clang having an Abort
   trap during buildworld's compile of gcrt1.s . (Reference
   material later, below.)

D) lldb crashes in llvm_unreachable in
   lldb::RegisterContextSP FreeBSDThread::GetRegisterContext()
   on powerpc64. (Reference material later, below.)

So I've not managed to check the backtrace for the
segmentation fault in the short example.



For reference . . .


For (C) ( -gdwarf-2 use ):

QUOTES
(gdb) bt
#0  thr_kill () at thr_kill.S:3
#1  0x000000000474afcf in __raise (s=6) at /usr/src/lib/libc/gen/raise.c:52
#2  0x00000000046cd386 in abort () at /usr/src/lib/libc/stdlib/abort.c:79
#3  0x00000000047394ba in __assert (func=<optimized out>, file=<optimized out>, line=<optimized out>, failedexpr=<optimized out>) at /usr/src/lib/libc/gen/assert.c:51
#4  0x000000000429aa9f in resetRootFile () at /usr/src/contrib/llvm/include/llvm/MC/MCDwarf.h:316
#5  parseDirectiveFile () at /usr/src/contrib/llvm/lib/MC/MCParser/AsmParser.cpp:3377
#6  parseStatement () at /usr/src/contrib/llvm/lib/MC/MCParser/AsmParser.cpp:2023
#7  0x000000000428cc12 in Run () at /usr/src/contrib/llvm/lib/MC/MCParser/AsmParser.cpp:884
#8  0x000000000163c649 in ExecuteAssembler () at /usr/src/contrib/llvm/tools/clang/tools/driver/cc1as_main.cpp:503
#9  cc1as_main () at /usr/src/contrib/llvm/tools/clang/tools/driver/cc1as_main.cpp:589
#10 0x0000000001643d10 in ExecuteCC1Tool () at /usr/src/contrib/llvm/tools/clang/tools/driver/driver.cpp:312
#11 main () at /usr/src/contrib/llvm/tools/clang/tools/driver/driver.cpp:382

  void resetRootFile() {
    assert(Header.MCDwarfFiles.empty());
    Header.RootFile.Name.clear();
    Header.resetMD5Usage();
    Header.HasSource = false;
  }

--- lib/csu__L ---
cc: error: unable to execute command: Abort trap (core dumped)
cc: error: clang integrated assembler command failed due to signal (use -v to see invocation)
FreeBSD clang version 8.0.0 (branches/release_80 355677) (based on LLVM 8.0.0)
Target: powerpc64-unknown-freebsd13.0
Thread model: posix
InstalledDir: /usr/bin
cc: note: diagnostic msg: PLEASE submit a bug report to https://bugs.freebsd.org/submit/ and include the crash backtrace, preprocessed source, and associated run script.
cc: note: diagnostic msg: Error generating preprocessed source(s) - no preprocessable inputs.
*** [gcrt1.o] Error code 254

make[5]: stopped in /usr/src/lib/csu/powerpc64
.ERROR_TARGET='gcrt1.o'
.ERROR_META_FILE='/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/lib/csu/powerpc64/gcrt1.o.meta'
.MAKE.LEVEL='5'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes verbose'
_ERROR_CMD='cc -gdwarf-2 -target powerpc64-unknown-freebsd13.0 --sysroot=/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp -B/usr/local/powerpc64-unknown-freebsd13.0/bin/ -O2 -pipe -I/usr/src/lib/csu/common -I/usr/src/lib/libc/include -mlongcall -DCRT_IRELOC_SUPPRESS -std=gnu99 -Wsystem-headers -Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wunused-parameter -Wcast-align -Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls -Wold-style-definition -Wno-pointer-sign -Wthread-safety -Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable -Qunused-arguments   -c -o gcrt1.o gcrt1.s;'
.CURDIR='/usr/src/lib/csu/powerpc64'
.MAKE='make'
.OBJDIR='/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/lib/csu/powerpc64'
.TARGETS='all'
DESTDIR='/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp'
LD_LIBRARY_PATH=''
MACHINE='powerpc'
MACHINE_ARCH='powerpc64'
MAKEOBJDIRPREFIX=''
MAKESYSPATH='/usr/src/share/mk'
MAKE_VERSION='20181221'
PATH='/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/usr/sbin:/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/usr/bin:/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/legacy/usr/sbin:/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/legacy/usr/bin:/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64/tmp/legacy/bin::/sbin:/bin:/usr/sbin:/usr/bin'
SRCTOP='/usr/src'
OBJTOP='/usr/obj/powerpc64vtsc_clang_altbinutils/powerpc.powerpc64/usr/src/powerpc.powerpc64'
.MAKE.MAKEFILES='/usr/src/share/mk/sys.mk /usr/src/share/mk/local.sys.env.mk /usr/src/share/mk/src.sys.env.mk /root/src.configs/src.conf.powerpc64-clang_altbinutils-bootstrap.amd64-host /usr/src/share/mk/bsd.mkopt.mk /usr/src/share/mk/src.sys.obj.mk /usr/src/share/mk/auto.obj.mk /usr/src/share/mk/bsd.suffixes.mk /root/src.configs/make.conf /usr/src/share/mk/local.sys.mk /usr/src/share/mk/src.sys.mk /dev/null /usr/src/lib/csu/powerpc64/Makefile /usr/src/share/mk/bsd.lib.mk /usr/src/share/mk/bsd.init.mk /usr/src/share/mk/bsd.opts.mk /usr/src/share/mk/bsd.cpu.mk /usr/src/share/mk/local.init.mk /usr/src/share/mk/src.init.mk /usr/src/lib/csu/powerpc64/../Makefile.inc /usr/src/share/mk/src.opts.mk /usr/src/share/mk/bsd.own.mk /usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.linker.mk /usr
 /src/lib/csu/powerpc64/../../Makefile.inc /usr/src/share/mk/bsd.libnames.mk /usr/src/share/mk/src.libnames.mk /usr/src/share/mk/bsd.symver.mk /usr/src/share/mk/bsd.nls.mk /usr/src/share/mk/bsd.confs
 .mk /usr/src/share/mk/bsd.files.mk /usr/src/share/mk/bsd.dirs.mk /usr/src/share/mk/bsd.incs.mk /usr/src/share/mk/bsd.links.mk /usr/src/share/mk/bsd.dep.mk /usr/src/share/mk/bsd.clang-analyze.mk /usr/src/share/mk/bsd.obj.mk /usr/src/share/mk/bsd.subdir.mk /usr/src/share/mk/bsd.sys.mk'
.PATH='. /usr/src/lib/csu/powerpc64 /usr/src/lib/csu/common'
1 error
END QUOTES


For (D) (lldb):

QUOTES
CPU not supported
UNREACHABLE executed at /usr/src/contrib/llvm/tools/lldb/source/Plugins/Process/FreeBSD/FreeBSDThread.cpp:192!
Abort trap (core dumped)

(gdb) bt
#0  0x0000000813715208 in .__sys_thr_kill () at thr_kill.S:3
#1  0x00000008137147cc in __raise (s=<optimized out>) at /usr/src/lib/libc/gen/raise.c:52
#2  0x000000081366b5d8 in abort () at /usr/src/lib/libc/stdlib/abort.c:79
#3  0x0000000011df6fb8 in llvm::llvm_unreachable_internal () at /usr/src/contrib/llvm/lib/Support/ErrorHandling.cpp:222
#4  0x00000000103aaaf8 in FreeBSDThread::GetRegisterContext () at /usr/src/contrib/llvm/tools/lldb/source/Plugins/Process/FreeBSD/FreeBSDThread.cpp:192
#5  0x00000000105807d4 in lldb_private::Thread::SetupForResume () at /usr/src/contrib/llvm/tools/lldb/source/Target/Thread.cpp:613
#6  0x0000000010571bc8 in lldb_private::ThreadList::WillResume () at /usr/src/contrib/llvm/tools/lldb/source/Target/ThreadList.cpp:541
#7  0x00000000105da23c in lldb_private::Process::PrivateResume () at /usr/src/contrib/llvm/tools/lldb/source/Target/Process.cpp:3281
#8  0x00000000105a00c8 in lldb_private::Target::Launch () at /usr/src/contrib/llvm/tools/lldb/source/Target/Target.cpp:2922
#9  0x000000001073f550 in CommandObjectProcessLaunch::DoExecute () at /usr/src/contrib/llvm/tools/lldb/source/Commands/CommandObjectProcess.cpp:221
#10 0x00000000106c36c4 in lldb_private::CommandObjectParsed::Execute () at /usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandObject.cpp:975
#11 0x00000000106d8b44 in lldb_private::CommandInterpreter::HandleCommand () at /usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp:1761
#12 0x00000000106da0a0 in lldb_private::CommandInterpreter::IOHandlerInputComplete () at /usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp:2801
#13 0x00000000107c0a08 in lldb_private::IOHandlerEditline::Run () at /usr/src/contrib/llvm/tools/lldb/source/Core/IOHandler.cpp:558
#14 0x0000000010346e5c in lldb_private::Debugger::ExecuteIOHandlers () at /usr/src/contrib/llvm/tools/lldb/source/Core/Debugger.cpp:988
#15 0x00000000106c8ddc in lldb_private::CommandInterpreter::RunCommandInterpreter () at /usr/src/contrib/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp:3003
#16 0x000000001034feb4 in lldb::SBDebugger::RunCommandInterpreter () at /usr/src/contrib/llvm/tools/lldb/source/API/SBDebugger.cpp:935
#17 0x00000000101de878 in Driver::MainLoop () at /usr/src/contrib/llvm/tools/lldb/tools/driver/Driver.cpp:756
#18 0x00000000101a0088 in main () at /usr/src/contrib/llvm/tools/lldb/tools/driver/Driver.cpp:936

lldb::RegisterContextSP FreeBSDThread::GetRegisterContext() {
  if (!m_reg_context_sp) {
    m_posix_thread = nullptr;

    RegisterInfoInterface *reg_interface = nullptr;
    const ArchSpec &target_arch = GetProcess()->GetTarget().GetArchitecture();

    switch (target_arch.GetMachine()) {
    case llvm::Triple::aarch64:
      reg_interface = new RegisterInfoPOSIX_arm64(target_arch);
      break;
    case llvm::Triple::arm:
      reg_interface = new RegisterInfoPOSIX_arm(target_arch);
      break;
    case llvm::Triple::ppc:
#ifndef __powerpc64__
      reg_interface = new RegisterContextFreeBSD_powerpc32(target_arch);
      break;
#endif
    case llvm::Triple::ppc64:
      reg_interface = new RegisterContextFreeBSD_powerpc64(target_arch);
      break;
    case llvm::Triple::mips64:
      reg_interface = new RegisterContextFreeBSD_mips64(target_arch);
      break;
    case llvm::Triple::x86:
      reg_interface = new RegisterContextFreeBSD_i386(target_arch);
      break;
    case llvm::Triple::x86_64:
      reg_interface = new RegisterContextFreeBSD_x86_64(target_arch);
      break;
    default:
      llvm_unreachable("CPU not supported");
    }
END QUOTES.




===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)

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