[Bug 212330] lang/gcc6: armv6 g++ 6.2.0 compiled ~10 line std::async using program gets SIGSEGV (but amd64 works)
bugzilla-noreply at freebsd.org
bugzilla-noreply at freebsd.org
Fri Sep 2 12:17:42 UTC 2016
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212330
Bug ID: 212330
Summary: lang/gcc6: armv6 g++ 6.2.0 compiled ~10 line
std::async using program gets SIGSEGV (but amd64
works)
Product: Ports & Packages
Version: Latest
Hardware: arm
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: Individual Port(s)
Assignee: gerald at FreeBSD.org
Reporter: markmi at dsl-only.net
Assignee: gerald at FreeBSD.org
Flags: maintainer-feedback?(gerald at FreeBSD.org)
The following ~10 line program also shows the SIGSEGV behavior on armv6 (an
rpi2) for running ./a.out after compiling via g++6. built with the system
clang++ 3.8.0 does not have such problems. The program is a vast simplification
of the original program that the crash was first discovered with.
# more g++6_build_crashes.cpp
#include <future> // future, async,
launch::async
static void f() {}
int main(int, const char* [])
{
auto a0{ std::async( std::launch::async, f ) };
a0.get();
return 0;
}
# /usr/local/bin/gdb a.out
GNU gdb (GDB) 7.11.1 [GDB v7.11.1 for FreeBSD]
. . .
(gdb) run
Starting program: /root/c_tests/a.out
[New LWP 100188 of process 2253]
Thread 2 received signal SIGSEGV, Segmentation fault.
[Switching to LWP 100188 of process 2253]
0x00000000 in ?? ()
(gdb) info threads
Id Target Id Frame
1 LWP 100172 of process 2253 0x00000000 in ?? ()
* 2 LWP 100188 of process 2253 0x00000000 in ?? ()
(gdb) thread 1
[Switching to thread 1 (LWP 100172 of process 2253)]
#0 0x00000000 in ?? ()
(gdb) bt
#0 0x00000000 in ?? ()
#1 0x200b8acc in _pthread_once (once_control=<optimized out>,
init_routine=<optimized out>) at /usr/src/lib/libthr/thread/thr_once.c:95
#2 0x00011b14 in __gthread_once (__once=0x20824030, __func=0x11660
<__once_proxy at plt>) at
/usr/local/lib/gcc6/include/c++/armv6-portbld-freebsd11.0/bits/gthr-default.h:699
#3 0x0001440c in std::call_once<void (std::thread::*)(),
std::thread*>(std::once_flag&, void (std::thread::*&&)(), std::thread*&&)
(__once=...,
__f=<unknown type in /root/c_tests/a.out, CU 0x0, DIE 0x11213>,
__args#0=<unknown type in /root/c_tests/a.out, CU 0x0, DIE 0x11207>) at
/usr/local/lib/gcc6/include/c++/mutex:619
#4 0x00013004 in std::__future_base::_Async_state_commonV2::_M_join
(this=0x2082400c) at /usr/local/lib/gcc6/include/c++/future:1644
#5 0x00012fb4 in std::__future_base::_Async_state_commonV2::_M_complete_async
(this=0x2082400c) at /usr/local/lib/gcc6/include/c++/future:1642
#6 0x000128ac in std::__future_base::_State_baseV2::wait (this=0x2082400c) at
/usr/local/lib/gcc6/include/c++/future:325
#7 0x00013b3c in std::__basic_future<void>::_M_get_result (this=0xbfbfed38) at
/usr/local/lib/gcc6/include/c++/future:687
#8 0x00012ec4 in std::future<void>::get (this=0xbfbfed38) at
/usr/local/lib/gcc6/include/c++/future:852
#9 0x00011df4 in main () at g++6_build_crashes.cpp:8
(gdb) thread 2
[Switching to thread 2 (LWP 100188 of process 2253)]
#0 0x00000000 in ?? ()
(gdb) bt
#0 0x00000000 in ?? ()
#1 0x200b8acc in _pthread_once (once_control=<optimized out>,
init_routine=<optimized out>) at /usr/src/lib/libthr/thread/thr_once.c:95
#2 0x00011b14 in __gthread_once (__once=0x20824024, __func=0x11660
<__once_proxy at plt>) at
/usr/local/lib/gcc6/include/c++/armv6-portbld-freebsd11.0/bits/gthr-default.h:699
#3 0x00013718 in std::call_once<void
(std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base,
std::__future_base::_Result_base::_Deleter> ()>*, bool*), s
td::__future_base::_State_baseV2*,
std::function<std::unique_ptr<std::__future_base::_Result_base,
std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void
(std::__future_base::_
State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base,
std::__future_base::_Result_base::_Deleter> ()>*, bool*),
std::__future_base::_State_baseV2*&&, std::function<std::un
ique_ptr<std::__future_base::_Result_base,
std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) (__once=...,
__f=<unknown type in /root/c_tests/a.out, CU 0x0, DIE 0x10fad>,
__args#0=<unknown type in /root/c_tests/a.out, CU 0x0, DIE 0x10c41>,
__args#1=<unknown type in /root/c_tests/a.out, CU 0x0, DIE 0x10f95>,
__args#2=<unknown type in /root/c_tests/a.out, CU 0x0, DIE 0x10fa1>) at
/usr/local/lib/gcc6/include/c++/mutex:619
#4 0x000129c4 in
std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base,
std::__future_base::_Result_base::_Deleter> ()>, bool) (
this=0x2082400c, __res=..., __ignore_failure=false) at
/usr/local/lib/gcc6/include/c++/future:393
#5 0x00017b6c in std::__future_base::_Async_state_impl<std::_Bind_simple<void
(*())()>, void>::_Async_state_impl(std::_Bind_simple<void
(*())()>&&)::{lambda()#1}::operator()() const ()
at /usr/local/lib/gcc6/include/c++/future:1664
#6 0x00019430 in
std::_Bind_simple<std::__future_base::_Async_state_impl<std::_Bind_simple<void
(*())()>, void>::_Async_state_impl(std::_Bind_simple<void
(*())()>&&)::{lambda()#1} ()>::_M_invoke<>(st
d::_Index_tuple<>) (this=0x2082500c) at
/usr/local/lib/gcc6/include/c++/functional:1400
#7 0x000192f4 in
std::_Bind_simple<std::__future_base::_Async_state_impl<std::_Bind_simple<void
(*())()>, void>::_Async_state_impl(std::_Bind_simple<void
(*())()>&&)::{lambda()#1} ()>::operator()()
(this=0x2082500c) at /usr/local/lib/gcc6/include/c++/functional:1389
#8 0x00018e68 in
std::thread::_State_impl<std::_Bind_simple<std::__future_base::_Async_state_impl<std::_Bind_simple<void
(*())()>, void>::_Async_state_impl(std::_Bind_simple<void (*())()>&&)::{lambda
()#1} ()> >::_M_run() (this=0x20825008) at
/usr/local/lib/gcc6/include/c++/thread:196
#9 0x201ac464 in std::execute_native_thread_routine (__p=0x20825008) at
/usr/obj/portswork/usr/ports/lang/gcc6/work/gcc-6.2.0/libstdc++-v3/src/c++11/thread.cc:83
#10 0x200affd4 in thread_start (curthread=<optimized out>) at
/usr/src/lib/libthr/thread/thr_create.c:289
#11 0x200afa90 in _pthread_create (thread=0xbfbfeb78, attr=<optimized out>,
start_routine=<optimized out>, arg=<optimized out>) at
/usr/src/lib/libthr/thread/thr_create.c:185
#12 0xbfbfeb5c in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
NOTE: kill or quit from gdb leads to gdb hanging, needing something like kill
-9 to deal with gdb.
NOTE: "/usr/local/bin/gdb a.out a.out.core" causes gdb itself to SIGSEGV. I've
no clue if this is an independent problem or not.
It only takes the one std::async use to have the problem. So far the above (and
the earlier variants) always crash with SIGSEGV on the rpi2 when the g++6
compiler was used to build.
As for the compile commands used:
g++6 -g -v -std=c++14 -Wpedantic -Wall -O2 -pthread
-Wl,-rpath=/usr/local/lib/gcc6 -mcpu=cortex-a7 g++6_build_crashes.cpp
Omitting the -mcpu=cortex-a7 still get the problem.
Using -O0 instead of -O2 still gets the problem.
But I'll note that my stable/11 -r304943 build and my ports builds (usr/ports
-r421001 vintage) were/are based on using -mcpu=cortex-a7 . Also the system
clang 3.8.0 was used to build g++6:
GNU C++14 (FreeBSD Ports Collection) version 6.2.0 (armv6-portbld-freebsd11.0)
compiled by GNU C version 4.2.1 Compatible FreeBSD Clang 3.8.0
(tags/RELEASE_380/final 262564), GMP version 5.1.3, MPFR version 3.1.4-p1, MPC
version 1.0.3, isl version none
# uname -apKU
FreeBSD rpi2 11.0-PRERELEASE FreeBSD 11.0-PRERELEASE #5 r304943M: Sun Aug 28
03:17:54 PDT 2016
markmi at FreeBSDx64:/usr/obj/clang/arm.armv6/usr/src/sys/RPI2-NODBG arm armv6
1100502 1100502
# svnlite info /usr/src | grep "Re[vl][ai:]"
Relative URL: ^/stable/11
Revision: 304943
Last Changed Rev: 304943
# svnlite info /usr/ports | grep "Re[vl][ai:]"
Relative URL: ^/head
Revision: 421001
Last Changed Rev: 421001
# more /etc/make.conf
DEFAULT_VERSIONS+=perl5=5.22
WRKDIRPREFIX=/usr/obj/portswork
WITH_DEBUG=
WITH_DEBUG_FILES=
MALLOC_PRODUCTION=
#
#system clang 3.8 (gcc6 rejects -march=armv7a):
#CFLAGS+= -march=armv7-a -mcpu=cortex-a7
#CXXFLAGS+= -march=armv7-a -mcpu=cortex-a7
#CPPFLAGS+= -march=armv7-a -mcpu=cortex-a7
#
#lang/gcc6's xgcc stage considers the above conflicting so use just:
CFLAGS+= -mcpu=cortex-a7
CXXFLAGS+= -mcpu=cortex-a7
CPPFLAGS+= -mcpu=cortex-a7
amd64 FreeBSD does not have this problem in my testing. Beyond amd64 FreeBSD
not having the problem that armv6 has. . .
I have since booted Ubuntu Mate 16.04 on the rpi2 (armv6 / cortex-a7) and
installed g++-6, g++-6 (Ubuntu 6.1.1-2ubuntu12~16.04) 6.1.1 20160510 since it
was available. (So not 6.2: not a full vintage match to my FreeBSD g++6
contexts, unfortunately.)
The original program that failed on FreeBSD when compiled with g++6 (v6.2) on
the same rpi2 executes just fine after being compiled on the Ubuntu Mate rpi2
configuration with g++-6 (v6.1).
So the armv6 SIGSEGV looks to not not be a generic g++6/libstdc++ problem for
std::async use: it seems to be armv6 FreeBSD specific. (Unfortunately I've not
been able to form fully matching versions for this comparison.)
I've also installed g++-6 on a ODROID-C2 (aarch64) Linux (Ubuntu 16.04.1) and
built the original program that I discovered the problem with. g++-6 (Ubuntu
6.1.1-2ubuntu12~16.04) 6.1.1 20160510 was the compiler.
It executes just fine on the ODROID-C2 under Ubuntu Mate. (So far as I know
FreeBSD does not support this type of context (yet) but it is the only aarch64
context I currently have access to.)
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