[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

Andrew Pinski  changed:

   What|Removed |Added

  Component|c++ |libstdc++

--- Comment #2 from Andrew Pinski  ---
Can you provide a compilable example?

[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[myLC at gmx dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

--- Comment #3 from myLC at gmx dot net ---
(In reply to Andrew Pinski from comment #2)
> Can you provide a compilable example?

Good point. The example works, hence the problem seems to be somewhere else:

#include 
#include 
#include 
#include 

std::optional< std::string > read( const std::filesystem::path &path, const
std::string &filename ) {
std::string s;
if( !filename.empty() ) {
std::filesystem::path file( path );
file /= filename;
if( std::filesystem::exists( file ) ) {
std::ifstream input( std::filesystem::absolute( file )
);
std::stringstream buffer;
buffer << input.rdbuf();
if( input.bad() )
goto errout;
s = buffer.str();
}
} else {
errout: return {};
}
return s;
}

int main( int argc, char **argv ) {
std::string read_write_test;
if( auto rwt = read( "./", argv[ 0 ] ) )
read_write_test = *rwt;
if( !read_write_test.empty() )
  std::cout << "fine" << std::endl;
return 0;
}

I need to investigate this further...

[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[myLC at gmx dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

myLC at gmx dot net changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution|--- |WORKSFORME

--- Comment #4 from myLC at gmx dot net ---
The example works with the same path. The real code is correct, though.
I'm guessing this might have something to do with a 3rd-party library
corrupting memory, The library needs to be built with the same compiler and
options (Nana C++).
I need to rebuild that thing and see, if this fixes it.
I apologize. I should have created an example first.

[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

--- Comment #5 from Jonathan Wakely  ---
Is it possible you're mixing code compiled with GCC 8 and GCC 9? In general
that works, but not for the new C++17 components that were still experimental
in GCC 8, such as filesystem::path.

Valgrind might give you more information about the crash, to help debug the
problem.

[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[myLC at gmx dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

--- Comment #6 from myLC at gmx dot net ---
I'm afraid that wasn't it. I rebuilt the Nana (GUI) library with the same
compiler (gcc/c++-9.1.0) and I'm still facing the same problem.

Valgrind croaked with 'Process finished with exit code 9', which makes sense.
The output shows the 'Invalid read of size 8' ( if (__ptr != nullptr) ) in
unique_ptr.h:
std::unique_ptr::~unique_ptr()
std::filesystem::path::_List::~_List()
std::filesystem::path::~path()
std::filesystem::current_path(std::error_code&) 
std::filesystem::current_path() 
std::filesystem::absolute(std::filesystem::path const&) 
Config::read(std::filesystem::path const&, std::string const&) 
main 
Address 0xb is not stack'd, malloc'd or (recently) free'd

I'm in for a lot of fun, it seems...

[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

--- Comment #7 from Jonathan Wakely  ---
It could also be Bug 90557 (which is fixed in the gcc-9-branch but present in
the gcc 9.1.0 release) but the symptoms don't look similar.

[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[myLC at gmx dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

--- Comment #8 from myLC at gmx dot net ---
(In reply to Jonathan Wakely from comment #7)
> It could also be Bug 90557 (which is fixed in the gcc-9-branch but present
> in the gcc 9.1.0 release) but the symptoms don't look similar.

This is possible. I built 9.1.0 from source and got new issues, though. Chances
are, my system could be too old.
I'm moving back to gcc-8 until I've updated. This feels too much like poking
around in the dark.

[Bug libstdc++/90646] std::filesystem::absolute( "yourpathhere" ) segfaults

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90646

--- Comment #9 from Jonathan Wakely  ---
(In reply to myLC from comment #8)
> This is possible. I built 9.1.0 from source and got new issues, though.
> Chances are, my system could be too old.

The std::filesystem code (and everything else in libstdc++) should work fine on
old systems, albeit with slightly degraded functionality or less efficient
implementations for some features.

I'll leave it with you, please feel free to reopen this bug if you do find a
problem in GCC.