From befe886cfb3650d7147830628ed19232c453dabe Mon Sep 17 00:00:00 2001 From: Melody Horn Date: Mon, 19 Oct 2020 23:47:51 -0600 Subject: i am growing tired of this project --- _posts/2020-10-19-crowbar-3-this-is-tough.md | 46 ++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) create mode 100644 _posts/2020-10-19-crowbar-3-this-is-tough.md (limited to '_posts') diff --git a/_posts/2020-10-19-crowbar-3-this-is-tough.md b/_posts/2020-10-19-crowbar-3-this-is-tough.md new file mode 100644 index 0000000..1c8f12c --- /dev/null +++ b/_posts/2020-10-19-crowbar-3-this-is-tough.md @@ -0,0 +1,46 @@ +--- +title: "Crowbar: Turns out, language development is hard" +--- + +(Previously in Crowbar: [Defining a good C replacement]({% link _posts/2020-09-28-crowbar-1-defining-a-c-replacement.md %}), [Simplifying C's type names]({% link _posts/2020-10-13-crowbar-3-this-is-tough.md %})) + +Originally, I hadn't decided whether Crowbar should be designed with an eye towards compiling to C or with an eye towards compiling directly. +Compiling to C massively cuts down the scope of Crowbar as a project, but compiling directly gives me more comprehensive control over what all happens. + +I figured I wouldn't need comprehensive control over everything, so I chose compiling to C, and then almost immediately ran into a pile of issues that compiling to C brings with it. + +## libc is part of the problem + +One of the goals I had for Crowbar was memory safety - most of the footguns in C are of the dubious-memory-operations variety - but it turns out you can't just duct tape memory safety to an existing language and call it a day. +Among the most easily-exploited class of dubious memory operations is the buffer overflow, and the most straightforward fix is bounds checking. + +However, most of the C standard library doesn't perform bounds checking, because the C standard library was designed in the 1600s when every CPU cycle took six months and compiler optimizations hadn't been invented yet. + +The C11 specification actually defines bounds-checking-performing alternatives to some of the standard library APIs, but it's optional (filed away in Annex K) and fuckin nobody can be bothered to implement it. +Some of the spec authors [wrote a whole investigation](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1969.htm) of why nobody uses Annex K, and it all boils down to "error handling in C is broken-by-default" - which is the other big issue Crowbar will have to solve, and I haven't even begun to think about how to do that. + +But. +We live in a world where C already exists in all its mixed glory, and in that world, nothing supports Annex K. +There exist some tacked-on implementations, but the [most complete-looking one](https://github.com/sbaresearch/slibc) is licensed under the regular GPL, not even the LGPL, which would be a problem for a lot of software. +So if I want Crowbar to be designed to compile into C, I need to either reimplement Annex K my damn self or design some equivalent APIs and implement those. + +In either case, now Crowbar has a runtime library on top of libc, and nobody's going to already have it so it'll have to figure out how to ensure that its runtime library is available wherever needed. +And that's a pain in the ass. + +## you can't win + +Okay, so if compiling to C would still require a runtime library, and ensuring that the runtime library still worked in mixed-Crowbar-and-C and fully-Crowbar projects without requiring system-wide installation or anything would be a nuisance, why not just simplify some things and skip over C? + +Well, for an ordinary language, that'd work rather well, which is why fucking nothing uses C as a compile target. +But one of the nonnegotiable goals of Crowbar is to have low- or no-effort C interoperability. +As such, you need to be able to include regular C headers. +But loading and parsing regular C headers means the Crowbar compiler needs to be able to understand all of C, and either implement or shell out to a C preprocessor that can use conventional command line arguments to define include directories. +And if the compiler has to encompass all of the complexity of C, then Crowbar just went from a subset of C to a superset of C. +I do not want to write a C compiler. +If Crowbar is supposed to be simpler than C, then writing a Crowbar compiler should be simpler than writing a C compiler, not more complicated. + +So compiling to C creates problems, and compiling not-to-C creates problems. +This sucks. +Send help. + +No, seriously, if you have advice, even if it's just "well I'd probably do this because it seems more intuitive to me", [send it in](mailto:~boringcactus/crowbar-lang-devel@lists.sr.ht). -- cgit v1.2.3