Hi,
Congcong Kuo <[email protected]> writes:
> In nix/libutil/util.cc there are lots of functions related to
> copy/delete files and manipulate file paths. In C++ 17 the standard
> library’s <filesystem> provides the same functionality which is more
> reliable.
>
> guix-daemon uses Boost.Format to generate formatted string. These code
> are copied into nix/libformat directly and I think it is not a good
> practice. With C++ 20 we can use <format> from C++’s standard
> library. I have done some experiments on it [2]. In my code repo I
> replace all boost::format with std::format in nix/libutil.
>
> We can use <filesystem> if we upgrade from —std=c++11 to -std=c++17. For
> <format> we need GCC 13 with -std=c++20.
In general I would consider the C++ daemon code to be read-only, though
in practice it’s been changing quite a bit lately; I would remain mostly
conservative though.
My take:
1. Yes to ‘-std=c++17’ and any change required to make that work.
2. Using ‘std::format’ would be nice, *if* that works with GCC 11, as
Efraim wrote.
3. I’m reluctant about using <filesystem> because the few functions
you mention are security-sensitive. We would need to look at the
implementation of libstdc++ and perhaps at the spec to see whether
their counterpart is appropriate.
Thoughts?
Ludo’.
