On Mon, 2025-02-03 at 09:46 +0000, JohnyTheCarrot via Gcc wrote: > Dear GCC Developers,
Hi Tuur > > I'm in the process of writing my own C compiler for educational > purposes. > To this end, I have decided to integrate into my compiler my own C++ > port ( https://github.com/johnythecarrot/mjolnir ) of the Rust crate > Ariadne ( https://github.com/zesterer/ariadne ) which provides nice, > fancy and readable diagnostics for use in compilers and the like. See > the first link for an idea of how my library outputs diagnostics. That output looks great, thanks! There are some ideas in there I may borrow for use in GCC - we're always looking for inspiration :) How does mjolnir handle C++ template errors? C++ compilers have an alarming tendency to spam the user with multiple pages of output on even simple errors, and I wonder if you've got any ideas on this. FWIW we're working towards addressing this in GCC; see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116253 and an example here: https://godbolt.org/z/xs4Gr6n6K Have you looked into supporting SARIF as a machine-readable output format? GCC supports capturing most of this "rich" diagnostic information in its SARIF output; see e.g. https://gcc.gnu.org/wiki/SARIF (or indeed, as a input format, for pretty output of SARIF log files?) > > I had the idea of perhaps contributing this diagnostics system to GCC > in one way or another, under a flag perhaps, but considered it might > be an unwelcome addition. I was told that there's no harm in raising > it with the GCC developers. > > This message serves as a gauge of interest from the GCC developers > for something of this kind. I am aware the current format of my > diagnostics do not comply with the GNU Standards, and I'd therefore > also like to politely ask for input on your suggestions on making it > comply while retaining its cleanliness. I'm the maintainer of GCC's diagnostics subsystem, and since GCC 6 (?) have been adding things like support for underlined ranges, fix-it hints, and so forth. I confess that while I'm aware that there are some GNU standards for diagnostics online somewhere, I've largely been ignoring them, to focus on adding new features (what the kids today call "velocity") whilst retaining compatibility within a >35 year old codebase, and to try to improve the user-experience; FWIW I've written a UX guide here for GCC here: https://gcc.gnu.org/onlinedocs/gccint/User-Experience-Guidelines.html In GCC 15 we've added some support for lines showing control flow, and for colorized labels highlighting and contrasting different syntactic elements; see e.g.: https://gcc.gnu.org/wiki/cauldron2024talks?action=AttachFile&do=get&target=2024-Cauldron-diagnostics-talk.pdf and the "ASCII" art for buffer overflows added in GCC 14 here: https://developers.redhat.com/articles/2024/04/03/improvements-static-analysis-gcc-14-compiler#visualizing_buffer_overflows > > I am the sole developer of Mjolnir and can therefore relicense it as > necessary. Mjolnir still has a couple of issues to iron out and > features to implement, such as multi-line span displaying. Licensing (under a GPL-compatible license) isn't an issue so much as implementation language. GCC has rather conservative build requirements, since we must be buildable of a wide variety of old machines with hundreds of configure-time variants. Although we implement the very latest versions of C++ and have the beginnings of Rust support, we implement all this in a subset of C++14 (and until recently this was only C++11), and this subset has to be compatible with a few other tools. So, sadly, implementing core GCC functionality in Rust isn't an option at this point (I wish it were, but I don't see it happening any time soon, I'm afraid). That said, I really like what you're doing. >From am implementation point of view, GCC has a text_art::canvas class for "painting" colorized text to a buffer with random access for output to a stream, and a text_art::widget class for doing hierarchical dynamic sizing of drawing elements. There's also a rich_location class which is used by diagnostics that are doing anything "fancy", though perhaps this could be refactored into an API similar to ariadne's (or one of the similar projects). Hope this is constructive; thanks again for the links, and good luck with mjolnir. Dave
