 | Nixpkgs Stdenv | 220 Members |
| 70 Servers |
| Nixpkgs Stdenv | 220 Members |
| 70 Servers |
| Sender | Message | Time |
|---|---|---|
| 27 Oct 2024 | ||
 Artturin |
| 21:58:55 |
| Artturin | * isysroot
| 21:59:04 |
 @trofi:matrix.org | TIL | 22:00:03 |
| @trofi:matrix.org | I wonder how transitive library dependencies are handled there. | 22:00:29 |
 emily | I didn't know Darwin handled it differently but that makes sense… | 22:00:54 |
| emily | in a messed up kind of way | 22:00:59 |
| emily | In reply to @trofi:matrix.orgwhat kind of changes do you think we might need to make something like this work for us? we could patch in a semantics change, but that's kinda gross. | 22:01:58 |
| @trofi:matrix.org | I don't know :) | 22:03:18 |
| emily | fair enough :) | 22:04:25 |
| emily | I would really like to work with the compilers' mechanisms rather than saying "hey, stuff is in /" and post-facto filtering out everything in / | 22:04:52 |
| @trofi:matrix.org | Yeah. Unfortunately compilers (and linkers) assume quite a bit about FHS layout: ld.so location, crt?.o file lookup, executable tools (as) lookup, etc. I'd say adding the proper knobs to upstreams (like an arbitrary --prefix= for these things instead of hardcoded paths with various inference rules) might be the best long-term option. But they have to be designed carefully to be compatible (or at least non-conflictings) with --sysroot= stuff, cross-compiling directory switch, multilib switch, etc. | 22:10:21 |
| emily | right. | 22:11:11 |
| emily | in Darwin we have the situation where we have switched to assembling a "normal"-structured sysroot for the basic system library set – which in our case is not FHS but instead the Xcode SDK layout – because it is much more compatible with build systems (and anyway contains only headers and stub libraries) | 22:12:13 |
| emily | which meant having to patch the purity filter to be aware of the fact that things like -L/usr/lib/swift are relative to that sysroot and therefore shouldn't be filtered | 22:12:36 |
| emily | I'd love to do more working with upstreams to get the appropriate knobs for our toolchains. I would be happiest if we didn't have wrappers at all | 22:13:04 |
| emily | but the state where we have a half-broken command-line parser just to filter out build systems that pass in -I/usr/whatever in non-build development shells on non-NixOS … is sad to me | 22:13:39 |
| @trofi:matrix.org | yeah, wrappers are a disaster | 22:13:42 |
| emily | the juice may be barely worth the squeeze, but I just spent several days fighting the squeeze on Darwin and it's been a pain | 22:14:12 |
| emily | and there's so many ways you can bypass it inadvertently to get a bad path into the argv anyway. | 22:14:26 |
| emily | so, one thing about the sysroot is that apparently at least on Darwin -isysroots stack, so we could do a thing where we pass one that just contains empty ./usr/lib etc., and overlay our SDK sysroot on top of that. I don't know if it's possible to do that with Linux toolchains, though. | 22:15:28 |
| emily | but if it is, we could maybe have such a stub sysroot to catch common errant -I and -L paths, and then "overlay" / on top to get DT_NEEDED etc. working? | 22:15:57 |
| emily | it's possible that all this is just weird Darwin-specific behaviour that we can't replicate on Linux though. | 22:16:10 |
| @trofi:matrix.org | I had an impression that to get a sysroot prefix addition on linux you need to add = in front, like -L=/usr/lib. Otherwise it will use unprefixed path. Linker scripts have an exception though that if the linker script is within the sysroot the prefix is added anyways even if = is not prepended: https://sourceware.org/binutils/docs/ld/File-Commands.html | 22:21:34 |
 Randy Eckenrode |
| 22:23:06 |
| Randy Eckenrode | That hurts my brain to parse. | 22:23:42 |
| @trofi:matrix.org | If a linker script is in sysroot directory and /foo paths will work like =/foo paths :) | 22:24:09 |
| @trofi:matrix.org | * If a linker script is in sysroot directory then any /foo paths will work like =/foo paths :) | 22:24:23 |
| emily | so you're saying we just need to put a linker script in there? :) | 22:25:03 |
| Randy Eckenrode | I think this is what I wanted.
If searchdir begins with = or $SYSROOT, then this prefix will be replaced by the sysroot prefix, controlled by the ‘--sysroot’ option, or specified when the linker is configured. | 22:25:25 |
| emily | oh, only for things the linker script references. | 22:25:27 |