[Bug libstdc++/92059] Crash on tr2::dynamic_bitset::operator=() with optimization

[jharris at simplexinvestments dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92059

--- Comment #11 from John Harris  ---
Great.  Thanks for the quick and thorough response.

[Bug libstdc++/92059] Crash on tr2::dynamic_bitset::operator=() with optimization

[jharris at simplexinvestments dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92059

--- Comment #6 from John Harris  ---
Thanks, JW.  While you're in there, the base class needs a copy constructor, as
its absence prevents use of the derived class copy constructor (won't compile).

[Bug middle-end/92059] Crash on tr2::dynamic_bitset::operator=() with optimization

[jharris at simplexinvestments dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92059

--- Comment #2 from John Harris  ---
I figured this out.  The assignment operator doesn't have a return statement.
Why that matters, I don't know.  But adding return *this fixes it.

[Bug c++/92059] New: Crash on tr2::dynamic_bitset::operator=() with optimization

[jharris at simplexinvestments dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92059

Bug ID: 92059
   Summary: Crash on tr2::dynamic_bitset::operator=() with
optimization
   Product: gcc
   Version: 8.3.1
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: jharris at simplexinvestments dot com
  Target Milestone: ---

Created attachment 47017
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47017&action=edit
Self-contained preprocesor output file

On CentOS7 x86_64, gcc 8.3.1, this simple program (.ii attached) causes a crash
on execution when built with any level of optimization greater than -O0.  It
seems to be in the vector assignment, but that works fine
outside of tr2::dynamic_bitset.

It also works fine if you specify a template parameter of uint8_t.  Both
valgrind and asan complain loudly on execution, and it throws a bad_alloc() as
the code is shown.

I used the latest source (for tr2::dynamic_bitset) from github, but it's the
same result as that found with the compiler distribution (devtoolset-8).

#define _GLIBCXX_NODISCARD [[nodiscard]]
#include "./dynamic_bitset"

int main()
{
  std::tr2::dynamic_bitset<> b1(1), b2(1);
  b2 = b1; // crash
  return 0;
}

Compiled with 
gcc (GCC) 8.3.1 20190311 (Red Hat 8.3.1-3)
g++ -O3 --std=c++17 main.ii -o main

$ ./main
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc
Aborted (core dumped)

g++ -O1 --std=c++17 main.ii -o main
$ ./main
Segmentation fault (core dumped)