https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67791
Bug ID: 67791
Summary: Crash using std::thread and iostream with dynamic
loading of a shared library
Product: gcc
Version: 5.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: nexyon at gmail dot com
Target Milestone: ---
Created attachment 36430
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36430&action=edit
the source of the shared library
If you think the summary of this bug is long/strange: yes, to me this seems
like the most weird bug, I have ever found.
What I am doing is the following:
* I have a main program (main.cpp) that loads a dynamic library thread.so and
calls a function in there.
* main.cpp also includes <iostream> without actually using this library.
(sounds weird, eh?)
* The function in thread.so creates a std::thread and runs it.
* The application crashes when the thread should be started.
Let me show you what happens (or: how to reproduce):
--------------
% g++ -g -fPIC -shared -o thread.so thread.cpp -std=c++11 -lpthread
% g++ -g -ldl -o main main.cpp
% gdb main
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Reading symbols from main...done.
(gdb) r
Starting program: /data/Work/Computer/Programming/Audaspace/bug/main
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt full
#0 0x0000000000000000 in ?? ()
No symbol table info available.
#1 0x00007ffff790e493 in __gthread_create (__args=<optimized out>,
__func=0x7ffff790e330 <std::(anonymous
namespace)::execute_native_thread_routine(void*)>, __threadid=0x7fffffffdd60)
at
/build/gcc-multilib/src/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/x86_64-unknown-linux-gnu/bits/gthr-default.h:662
No locals.
#2 std::thread::_M_start_thread (this=0x7fffffffdd60, __b=...) at
/build/gcc-multilib/src/gcc-5.2.0/libstdc++-v3/src/c++11/thread.cc:149
No locals.
#3 0x00007ffff6d99826 in std::thread::thread<void (&)(int, unsigned long
long*), int, unsigned long long*&>(void (&)(int, unsigned long long*), int&&,
unsigned long long*&) (this=0x7fffffffdd60, __f=
@0x7ffff6d993e2: {void (int, unsigned long long *)} 0x7ffff6d993e2
<factorial(int, unsigned long long*)>) at /usr/include/c++/5.2.0/thread:137
No locals.
#4 0x00007ffff6d99463 in run () at thread.cpp:17
a = 4196233
c = 0x7fffffffdd70
t1 = {_M_id = {_M_thread = 0}}
#5 0x0000000000400793 in main (argc=1, argv=0x7fffffffdea8) at main.cpp:9
handle = 0x612c40
run_func = 0x7ffff6d99430 <run()>
(gdb)
--------------
Now why is this weird/funny?
There are two ways you can get rid of the crash:
* the first is to add -lpthread to the second g++ line (the one that compiles
main.cpp and links the main program) OR
* you remove the line #include <iostream> in main.cpp
I found this bug in a way bigger code base as you can imagine and I already
spent a lot of time to get it down to this minimal example. I hope you can
find, what is the problem here! Thanks!
