[Bug 1824721] Re: g++-8 in disco is broken with libstdc++6 from gcc9 and libstdc++fs
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1824721 at bugs.launchpad.net
Wed Apr 17 02:33:07 UTC 2019
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On 2019-04-11T14:11:43+00:00 Mpreda wrote:
#include <filesystem>
int main() {
std::filesystem::path p = "foo";
}
g++ -g --std=c++17 path.cpp
./a.out
Segmentation fault (core dumped)
g++ --version
g++ (Ubuntu 8.3.0-6ubuntu1) 8.3.0
uname -a
Linux x2 5.0.6-050006-generic #201904030534 SMP Wed Apr 3 05:36:14 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Ubuntu 19.04.
Core was generated by `./a.out'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x000055c2ac25149b in std::vector<std::filesystem::__cxx11::path::_Cmpt, std::allocator<std::filesystem::__cxx11::path::_Cmpt> >::~vector (this=0x23, __in_chrg=<optimized out>) at /usr/include/c++/8/bits/stl_vector.h:567
567 std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
(gdb) bt
#0 0x000055c2ac25149b in std::vector<std::filesystem::__cxx11::path::_Cmpt, std::allocator<std::filesystem::__cxx11::path::_Cmpt> >::~vector (this=0x23, __in_chrg=<optimized out>) at /usr/include/c++/8/bits/stl_vector.h:567
#1 0x000055c2ac251314 in std::filesystem::__cxx11::path::~path (this=0x3, __in_chrg=<optimized out>) at /usr/include/c++/8/bits/fs_path.h:208
#2 0x000055c2ac251f5c in std::filesystem::__cxx11::path::_Cmpt::~_Cmpt (this=0x3, __in_chrg=<optimized out>) at /usr/include/c++/8/bits/fs_path.h:643
#3 0x000055c2ac251f77 in std::_Destroy<std::filesystem::__cxx11::path::_Cmpt> (__pointer=0x3) at /usr/include/c++/8/bits/stl_construct.h:98
#4 0x000055c2ac251e27 in std::_Destroy_aux<false>::__destroy<std::filesystem::__cxx11::path::_Cmpt*> (__first=0x3, __last=0x0) at /usr/include/c++/8/bits/stl_construct.h:108
#5 0x000055c2ac251a98 in std::_Destroy<std::filesystem::__cxx11::path::_Cmpt*> (__first=0x3, __last=0x0) at /usr/include/c++/8/bits/stl_construct.h:137
#6 0x000055c2ac2517a9 in std::_Destroy<std::filesystem::__cxx11::path::_Cmpt*, std::filesystem::__cxx11::path::_Cmpt> (__first=0x3, __last=0x0) at /usr/include/c++/8/bits/stl_construct.h:206
#7 0x000055c2ac2514b1 in std::vector<std::filesystem::__cxx11::path::_Cmpt, std::allocator<std::filesystem::__cxx11::path::_Cmpt> >::~vector (this=0x7ffe3ad201d0, __in_chrg=<optimized out>)
at /usr/include/c++/8/bits/stl_vector.h:567
#8 0x000055c2ac251314 in std::filesystem::__cxx11::path::~path (this=0x7ffe3ad201b0, __in_chrg=<optimized out>) at /usr/include/c++/8/bits/fs_path.h:208
#9 0x000055c2ac251230 in main () at path.cpp:4
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/0
------------------------------------------------------------------------
On 2019-04-12T10:50:39+00:00 Mpreda wrote:
I would hope somebody would take a look and reject this issues as
invalid for some reason, because otherwise it's rather severe.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/1
------------------------------------------------------------------------
On 2019-04-13T07:12:50+00:00 Mpreda wrote:
Adding -lstdc++fs fixes the problem with g++ 8.3
g++-9 does not segfault even without -lstdc++fs
g++-9 --version
g++-9 (Ubuntu 9-20190402-1ubuntu1) 9.0.1 20190402 (experimental) [trunk revision 270074]
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/2
------------------------------------------------------------------------
On 2019-04-13T08:10:35+00:00 Ufospoke wrote:
I just tried with g++ (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2) on Fedora
and it works well. But to be able to link, I had to add -lstdc++fs.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/3
------------------------------------------------------------------------
On 2019-04-16T10:20:33+00:00 Redi wrote:
The -lstdc++fs requirement for std::filesystem in GCC 8 is documented in
several places:
https://gcc.gnu.org/onlinedocs/gcc-8.3.0/libstdc++/manual/manual/using.html#manual.intro.using.flags
https://gcc.gnu.org/onlinedocs/gcc-8.3.0/libstdc++/manual/manual/status.html#status.iso.2017
https://gcc.gnu.org/onlinedocs/gcc-8.3.0/libstdc++/manual/manual/using_dynamic_or_shared.html#manual.intro.using.linkage.experimental
I don't know why it crashes with Ubuntu, it should be a linker error. I
suspect Ubuntu is doing something silly like providing libstdc++.so from
GCC 9, which defines std::filesystem::path differently, and so is not
compatible with C++17 code compiled using GCC 8.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/9
------------------------------------------------------------------------
On 2019-04-16T10:22:18+00:00 Redi wrote:
Although if you link with -lstdc++fs then it should work OK, because the
incompatible std::filesystem symbols in libstdc++.so.6.0.26 won't be
used.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/10
------------------------------------------------------------------------
On 2019-04-16T12:55:08+00:00 Mpreda wrote:
OK, thanks.
So if on Ubuntu 19.04, the default compiler produces without
errors/warnings, from valid source code, an executable that crashes,
that's programmer error?!
I understand the explanation, but there is a problem. Maybe the bug is
not with gcc but with Ubuntu, but a bug there is.
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/14
------------------------------------------------------------------------
On 2019-04-16T13:18:43+00:00 Redi wrote:
See https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721 where I
said:
"for now the short answer is "C++17 support in GCC 8 is experimental,
the onus is on you to link correctly"
Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-8/+bug/1824721/comments/15
** Changed in: gcc
Status: Unknown => Invalid
** Changed in: gcc
Importance: Unknown => Medium
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https://bugs.launchpad.net/bugs/1824721
Title:
g++-8 in disco is broken with libstdc++6 from gcc9 and libstdc++fs
Status in gcc:
Invalid
Status in gcc-8 package in Ubuntu:
Incomplete
Bug description:
There is a significant incompatibility here which leaves the default
C++ compiler broken with C++17 std::filesystem usage. Unfortunately,
there isn't an obvious workaround since there's only one libstdc++6
package, and it's using the non-default and unreleased GCC9 version of
libstdc++, making it impossible to use the compatible GCC8 version of
the library.
% cat testpath.cpp
#include <filesystem>
int main()
{
std::filesystem::path p("test");
}
g++-9 -std=c++17 -lstdc++fs -g3 -o testpath testpath.cpp
% ./testpath
% g++-8 -std=c++17 -lstdc++fs -g3 -o testpath testpath.cpp
% ./testpath
zsh: segmentation fault (core dumped) ./testpath
% gdb testpath
GNU gdb (Ubuntu 8.2.91.20190405-0ubuntu3) 8.2.91.20190405-git
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
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Reading symbols from testpath...
(gdb) run
Starting program: /tmp/testpath
Program received signal SIGSEGV, Segmentation fault.
0x000055555555649b in std::vector<std::filesystem::__cxx11::path::_Cmpt, std::allocator<std::filesystem::__cxx11::path::_Cmpt> >::~vector (this=0x23, __in_chrg=<optimised out>) at /usr/include/c++/8/bits/stl_vector.h:567
567 std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
(gdb) bt
#0 0x000055555555649b in std::vector<std::filesystem::__cxx11::path::_Cmpt, std::allocator<std::filesystem::__cxx11::path::_Cmpt> >::~vector (this=0x23, __in_chrg=<optimised out>) at /usr/include/c++/8/bits/stl_vector.h:567
#1 0x0000555555556314 in std::filesystem::__cxx11::path::~path (this=0x3, __in_chrg=<optimised out>)
at /usr/include/c++/8/bits/fs_path.h:208
#2 0x0000555555556f5c in std::filesystem::__cxx11::path::_Cmpt::~_Cmpt (this=0x3, __in_chrg=<optimised out>)
at /usr/include/c++/8/bits/fs_path.h:643
#3 0x0000555555556f77 in std::_Destroy<std::filesystem::__cxx11::path::_Cmpt> (__pointer=0x3)
at /usr/include/c++/8/bits/stl_construct.h:98
#4 0x0000555555556e27 in std::_Destroy_aux<false>::__destroy<std::filesystem::__cxx11::path::_Cmpt*> (
__first=0x3, __last=0x0) at /usr/include/c++/8/bits/stl_construct.h:108
#5 0x0000555555556a98 in std::_Destroy<std::filesystem::__cxx11::path::_Cmpt*> (__first=0x3, __last=0x0)
at /usr/include/c++/8/bits/stl_construct.h:137
#6 0x00005555555567a9 in std::_Destroy<std::filesystem::__cxx11::path::_Cmpt*, std::filesystem::__cxx11::path::_Cmpt> (__first=0x3, __last=0x0) at /usr/include/c++/8/bits/stl_construct.h:206
#7 0x00005555555564b1 in std::vector<std::filesystem::__cxx11::path::_Cmpt, std::allocator<std::filesystem::__cxx11::path::_Cmpt> >::~vector (this=0x7fffffffe310, __in_chrg=<optimised out>)
at /usr/include/c++/8/bits/stl_vector.h:567
#8 0x0000555555556314 in std::filesystem::__cxx11::path::~path (this=0x7fffffffe2f0, __in_chrg=<optimised out>)
at /usr/include/c++/8/bits/fs_path.h:208
#9 0x0000555555556230 in main () at testpath.cpp:5
(gdb) quit
A debugging session is active.
Inferior 1 [process 2414] will be killed.
Quit anyway? (y or n) y
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