null character at end of string from filesystem::temp_directory_path

[anonymous]

The null character at end of string causes very interesting bugs that are hard to debug.

Workaround we learned to use is .c_str():

filesystem::path temp_path = filesystem::temp_directory_path( ec ).c_str();

Cause of bug: GetTempPathW(0, 0) returns the size of buffer enought to contain the path, but is might be bigger than (path length + 1). (It rarely happens, but happens.) However the function filesystem::temp_directory_path expects it to be exactly (path length + 1).

Solution: replace lines

buf.pop_back(); path p(buf.begin(), buf.end());

with

path p(buf.begin());

[Beman Dawes]

Fixed. A path member function remove_trailing_separator() was added publicly since this may be useful to users.

Thanks,

--Beman

[anonymous]

The bug is not fixed as of version 1.57. It has nothing to do with `trailing separator'.

Again: `The null character at end of string causes very interesting bugs ...'.

The tested solution: replace lines

buf.pop_back();

path p(buf.begin(), buf.end());

with

path p(buf.begin());

in file \libs\filesystem\src\operations.cpp

The problem is that string returned by GetTempPathW sometimes contain 2 null characters. That means that 1 null character becomes a part of returned path in buggy code, because the code makes assumption that returned string contains exactly 1 null character.

...

Is explanation ok? Or should I just send a patch?

[Beman Dawes]

Oops! The trailing_separator comment applied to a different ticket.

Are you sure you are looking at the current state of filesystem? GetTempPathW is no longer used. Please take a look at the develop branch at ​https://github.com/boostorg/filesystem, and do submit a patch if you think there is still a problem, and then reopen the ticket again.

Thanks,

--Beman