On Thu, May 15, 2025 at 06:13:56PM +0800, Congcong Kuo wrote: > Hello Guix, > > Currently guix-daemon is built using GCC 11 with -std=c++11. We are waiting > for guile-daemon [1], but we can have improvements on guix-daemon right now. > > 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. > > WDYT? > > Regards, > Kuo > > [1]: https://guix.gnu.org/en/blog/2023/a-build-daemon-in-guile/ > [2]: > https://codeberg.org/congcongkuo/guix-daemon-zig/commit/38b8722f53d17ae4c5826dab051f4fdb00da31db
We currently have gcc-11 as our default gcc in Guix, so let's see if that's possible. Quoting from the gcc-11.5.0 manual[3]: By default, GCC also provides some additional extensions to the C++ language that on rare occasions conflict with the C++ standard. See Options Controlling C++ Dialect. Use of the -std options listed above disables these extensions where they they conflict with the C++ standard version selected. You may also select an extended version of the C++ language explicitly with -std=gnu++98 (for C++98 with GNU extensions), or -std=gnu++11 (for C++11 with GNU extensions), or -std=gnu++14 (for C++14 with GNU extensions), or -std=gnu++17 (for C++17 with GNU extensions), or -std=gnu++20 (for C++20 with GNU extensions). The default, if no C++ language dialect options are given, is -std=gnu++17. (It also mentions that you can use the c++ versions of these flags.) In nix/local.mk we have the following: # Use '-std=c++11' for 'std::shared_ptr', 'auto', lambdas, and more.¬ AM_CXXFLAGS = -Wall -std=c++11 (These lines are unchanged since May 2015.) gcc-10.5.0 doesn't give any mention of c++20/gnu++20, so it sounds like it would make gcc-11 the minimum version for building the daemon if we ditched Boost.Format and used <format>. I think overall it would be a good idea to not vendor that library, and this would allow us to do that. As far as packaging Guix in a foreign distro, I don't think it would be a problem to require such a "new" version of gcc. [3] https://gcc.gnu.org/onlinedocs/gcc-11.5.0/gcc/Standards.html#C_002b_002b-Language -- Efraim Flashner <efr...@flashner.co.il> אפרים פלשנר GPG key = A28B F40C 3E55 1372 662D 14F7 41AA E7DC CA3D 8351 Confidentiality cannot be guaranteed on emails sent or received unencrypted
signature.asc
Description: PGP signature
