gcc-7.1.0/c++17/old-abi: empty stringstream invalid memory access

gcc-7.1.0/c++17/old-abi: empty stringstream invalid memory access

[Irfan Adilovic]

I am reproducing here a bug report I filed to gcc's bugzilla against
gcc-7.1.0: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81522 , in
hopes of finding others who observed the same issue or who may have a
solution. The bug only appears on Cygwin and only in c++17 mode with
the old ABI.

-- Irfan

This trivial program:

#include <sstream>
int main() {
std::stringstream os; // same with ("") or (std::string())
os.str();
return 0;
}

causes an invalid memory access with gcc 7.1.0 (compiled from source),
but only on Cygwin in c++17 mode with old ABI, and only if the
stringstream is constructed empty. Changing any of those parameters no
longer causes the issue.

Thread 1 "string" received signal SIGABRT, Aborted.
0x00000001004018a0 in __gnu_cxx::new_allocator<char>::deallocate
(this=0x6, __p=0x3e8000003fc <error: Cannot access memory at address
0x3e8000003fc>)
at /usr/local/gcc-7.1.0/include/c++/7.1.0/ext/new_allocator.h:125
125 ::operator delete(__p);
(gdb) bt
#0 0x00000001004018a0 in __gnu_cxx::new_allocator<char>::deallocate
(this=0x6, __p=0x3e8000003fc <error: Cannot access memory at address
0x3e8000003fc>)
at /usr/local/gcc-7.1.0/include/c++/7.1.0/ext/new_allocator.h:125
#1 0x00000001800b25d2 in CreateEventW () from /usr/bin/cygwin1.dll
#2 0x0000000000000130 in ?? ()

$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/local/gcc-7.1.0/libexec/gcc/x86_64-pc-cygwin/7.1.0/lto-wrapper.exe
Target: x86_64-pc-cygwin
Configured with: ../configure --prefix=/usr/local/gcc-7.1.0
--enable-threads=posix --enable-checking=release
--enable-languages=c,c++ --build=x86_64-pc-cygwin --disable-multilib
--with-default-libstdcxx-abi=gcc4-compatible
Thread model: posix
gcc version 7.1.0 (GCC)

Sample program compiled with:

$ g++ -std=c++17 -D_GLIBCXX_USE_CXX11_ABI=0 -ggdb -O0 string.cc -o string

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: gcc-7.1.0/c++17/old-abi: empty stringstream invalid memory access

[Dan Kegel]

On Sun, Jul 23, 2017 at 4:38 AM, Irfan Adilovic <irfanadilovic@gmail.com> wrote:
> I am reproducing here a bug report I filed to gcc's bugzilla against
> gcc-7.1.0: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81522
> The bug only appears on Cygwin and only in c++17 mode with the old ABI.

Pedantic automated response:

Which version of cygwin?
See https://cygwin.com/problems.html

If you can minimize the test case further per
https://gcc.gnu.org/bugs/minimize.html
your bug may look more tempting to gcc developers.
- Dan

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: gcc-7.1.0/c++17/old-abi: empty stringstream invalid memory access

[David Stacey]

On 23/07/17 12:38, Irfan Adilovic wrote:
> I am reproducing here a bug report I filed to gcc's bugzilla against
> gcc-7.1.0:https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81522  , in
> hopes of finding others who observed the same issue or who may have a
> solution. The bug only appears on Cygwin and only in c++17 mode with
> the old ABI.

Earlier in the month, there were a few issues reported regarding g++ 
that turned out to be a problem in signal.h. This was fixed in Cygwin 
2.8.2. Please could you verify the version of Cygwin that you're using 
(cygcheck -c cygwin). If you have an older version of Cygwin, please 
could you update and re-run your testcase.

Dave.


--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple