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+---
+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).