Why is /sysdeps/unix/sysv/linux/x86_64/clone.S crashing with SIGSTOP at (disassembled) "test %rax,%rax" on Ubuntu 20.10 when running this auto generated minimal (no-qt) C++ application in Qt Creator 4.14.2 in DEBUG mode:
#include <iostream>
#include <thread>
void foo()
{
}
int main()
{
std::thread t(foo); // Crash happens after stepping over this line
t.join();
std::cout << "All good!" << std::endl;
return 0;
}
Callstack
1 clone clone.S 78 0x7f28abaef215
2 ?? allocatestack.c 313 0x7f28abbc94b0
3 ?? 0x7f28ab881640
4 ??
Disassembler for allocatestack.c stopped at:
pthread_create.c:
0x7f28abbc94b0 f3 0f 1e fa endbr64
Disassembler for clone.S stopped at "test %rax,%rax":
50 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891e0 f3 0f 1e fa endbr64
52 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891e4 <+ 4> 48 c7 c0 ea ff ff ff mov $0xffffffffffffffea,%rax
53 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891eb <+ 11> 48 85 ff test %rdi,%rdi
54 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891ee <+ 14> 74 3d je 0x7f2f1638922d <clone+77>
55 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891f0 <+ 16> 48 85 f6 test %rsi,%rsi
56 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891f3 <+ 19> 74 38 je 0x7f2f1638922d <clone+77>
59 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891f5 <+ 21> 48 83 ee 10 sub $0x10,%rsi
60 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891f9 <+ 25> 48 89 4e 08 mov %rcx,0x8(%rsi)
64 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f163891fd <+ 29> 48 89 3e mov %rdi,(%rsi)
67 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f16389200 <+ 32> 48 89 d7 mov %rdx,%rdi
68 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f16389203 <+ 35> 4c 89 c2 mov %r8,%rdx
69 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f16389206 <+ 38> 4d 89 c8 mov %r9,%r8
70 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f16389209 <+ 41> 4c 8b 54 24 08 mov 0x8(%rsp),%r10
71 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f1638920e <+ 46> b8 38 00 00 00 mov $0x38,%eax
76 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f16389213 <+ 51> 0f 05 syscall
78 [1] in ../sysdeps/unix/sysv/linux/x86_64/clone.S
0x7f2f16389215 <+ 53> 48 85 c0 test %rax,%rax
CMakeLists.txt
cmake_minimum_required(VERSION 3.5)
project(testThread LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
# These 3 lines were added by me to the auto generated CMakeLists.txt
set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
set(THREADS_PREFER_PTHREAD_FLAG TRUE) # Ensures that -pthread is added to the compile flags
find_package(Threads REQUIRED)
add_executable(testThread main.cpp)
target_link_libraries(testThread Threads::Threads)
CMake output
Running /usr/bin/cmake -S /home/myhome/testThread -B /home/myhome/testThread/build-debug '-GCodeBlocks - Ninja' -DCMAKE_BUILD_TYPE:String=Debug -DQT_QMAKE_EXECUTABLE:STRING= -DCMAKE_PREFIX_PATH:STRING= -DCMAKE_C_COMPILER:STRING=/usr/bin/gcc -DCMAKE_CXX_COMPILER:STRING=/usr/bin/g++ in /home/myhome/testThread/build-debug.
-- The CXX compiler identification is GNU 10.2.0
-- Check for working CXX compiler: /usr/bin/g++
-- Check for working CXX compiler: /usr/bin/g++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Looking for C++ include pthread.h
-- Looking for C++ include pthread.h - found
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Check if compiler accepts -pthread
-- Check if compiler accepts -pthread - yes
-- Found Threads: TRUE
-- Configuring done
-- Generating done
CMake Warning:
Manually-specified variables were not used by the project:
QT_QMAKE_EXECUTABLE
-- Build files have been written to: /home/myhome/testThread/build-debug
Elapsed time: 00:00.
CMake build output
17:24:26: Running steps for project testThread...
17:24:26: Starting: "/usr/bin/cmake" --build . --target all --verbose
[1/2 3.9/sec] /usr/bin/g++ -g -pthread -std=gnu++11 -MD -MT CMakeFiles/testThread.dir/main.cpp.o -MF CMakeFiles/testThread.dir/main.cpp.o.d -o CMakeFiles/testThread.dir/main.cpp.o -c ../main.cpp
[2/2 6.9/sec] : && /usr/bin/g++ -g CMakeFiles/testThread.dir/main.cpp.o -o testThread -pthread && :
17:24:26: The process "/usr/bin/cmake" exited normally.
17:24:26: Elapsed time: 00:00.
g++ Version
~$ g++ --version
g++ (Ubuntu 10.2.0-13ubuntu1) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
So far what I tried was creating this minimal example without using ccache and with an empty build folder but the issue persists. I am out of ideas.
Help is very appreciated!
UPDATE 1
Running in RELEASE mode in Qt Creator works fine
Running from terminal as suggested in the comments works fine
g++ -pthread -o testThread main.cpp
./testThread
Running from terminal with gdb works fine
$ gdb ./testThread
GNU gdb (Ubuntu 9.2-0ubuntu2) 9.2
Copyright (C) 2020 Free Software Foundation, Inc.
Reading symbols from ./testThread...
(gdb) r
Starting program: testThread
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff7a51640 (LWP 5946)]
[Thread 0x7ffff7a51640 (LWP 5946) exited]
All good!
[Inferior 1 (process 5942) exited normally]
(gdb)
UPDATE 2
Seems the issue is related to Qt Creator. There are two workarounds.
Add this to the "Debugging Helper Customization":
handle SIGSTOP pass nostop noprint
- Or disable the checkbox "Run in terminal" in the project's Run configuration
cmake?g++ -pthread -o testThread main.cpp– Hydrocortisone