Bug 90050 - std::filesystem::path segfault in destructor
Summary: std::filesystem::path segfault in destructor
Alias: None
Product: gcc
Classification: Unclassified
Component: libstdc++ (show other bugs)
Version: 8.3.0
: P3 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
Depends on:
Reported: 2019-04-11 14:11 UTC by Mihai Preda
Modified: 2019-04-29 15:21 UTC (History)
3 users (show)

See Also:
Known to work:
Known to fail:
Last reconfirmed:


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Description Mihai Preda 2019-04-11 14:11:43 UTC
#include <filesystem>

int main() {
  std::filesystem::path p = "foo";

g++ -g --std=c++17 path.cpp

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
Comment 1 Mihai Preda 2019-04-12 10:50:39 UTC
I would hope somebody would take a look and reject this issues as invalid for some reason, because otherwise it's rather severe.
Comment 2 Mihai Preda 2019-04-13 07:12:50 UTC
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]
Comment 3 Frédéric Bron 2019-04-13 08:10:35 UTC
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.
Comment 4 Jonathan Wakely 2019-04-16 10:20:33 UTC
The -lstdc++fs requirement for std::filesystem in GCC 8 is documented in several places:


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.
Comment 5 Jonathan Wakely 2019-04-16 10:22:18 UTC
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.
Comment 6 Mihai Preda 2019-04-16 12:55:08 UTC
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.
Comment 7 Jonathan Wakely 2019-04-16 13:18:43 UTC
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"
Comment 8 Matthias Klose 2019-04-29 15:21:01 UTC
that's now mitigated by a local patch, always linking with -lstdc++fs.