C++ compilers: Be sane with standard libraries by Ericson2314 · Pull Request #85189 · NixOS/nixpkgs

Ericson2314 · 2020-04-14T02:25:05Z

Motivation for this change

This is long overdue, @LnL7 Time for you to say "I told you so!" :).

Things done

Ericson2314 · 2020-04-14T02:28:53Z

Seeing that this is such a massive rebuild, on I am all ears on how we can do more nix and less bash to make the inevitable follow-up work easier.

Maybe we could purely concat lists for all those *flags file and write once? The building detection the wrapper script does currently I am not too pleased with.

pkgs/development/compilers/llvm/7/default.nix

matthewbauer · 2020-04-14T03:04:17Z

pkgs/top-level/all-packages.nix

We may need a migration or warning for this.

It may not be actively used though

aliases.nix should be enough.

I am not sure what should be aliased?

Not aliased but we need a throw statement in aliases.nix that generates a warning stating that this file has been removed.

Ah! sounds good.

pkgs/build-support/cc-wrapper/default.nix

matthewbauer · 2020-04-14T03:12:49Z

pkgs/build-support/cc-wrapper/default.nix

This may be used outside by wrappers outside of nixpkgs. might be worth keeping, but just as meta-information.

It might be, but I think that's bad :)

There's no good way to use libraries that want these c flags without some meta-info like this. For instance bindgen in rust or anything that uses libclang. If we're going to be removing it, we should at least have a replacement.

see #26474 for why this was exported

Right I would rather have a more general way to get flags and just this one in particular. The default part (i.e. miy get overriden) is no good too.

matthewbauer · 2020-04-14T03:19:21Z

pkgs/applications/networking/browsers/firefox/common.nix

Maybe we should just expose all of these flags in the cc-wrapper ? Something like stdenv.cc.cflags_compile and stdenv.cc.ld_flags

that is the pre-substituted values since we don't know the actual values at evaluation

It would be nice to uses more Nix so we did know the values. (e.g. have a nix boolean and then assert at run-time it was correct.)

I think that requires Nix-level setup-hooks to work correctly. I think that might be too ambitious for now.

I'm thinking something like /nix-support/get-cflags.sh which does all of this for you.

Well getting all the -I flags for other packaged requires that, but not just the std library stuff I think.

Right these should just need the basic c/c++ headers and library paths.

pkgs/os-specific/linux/firmware/fwupdate/default.nix

matthewbauer · 2020-04-14T20:05:02Z

I think we can also remove some of the old hacks like in https://github.com/NixOS/nixpkgs/pull/26709/files too

LnL7 · 2020-04-14T20:30:44Z

Does that change here? I would expect this to still only include it for clang++. Come to think of it, wouldn't CC=$CXX be a nicer fix for those cases or does that not work?

pkgs/build-support/cc-wrapper/cc-wrapper.sh

LnL7 · 2020-04-14T20:35:32Z

pkgs/build-support/cc-wrapper/default.nix

Would it make sense to expose the libc++ of the compiler, similar to libc?

Yeah, though null for libstdc++ is rather unfortunate. Oh well, all the more reason to get on splitting up the GCC derivation.

Perhaps for now cc.libcxx = gcc would make sense? Maybe that could also solve cc ? gcc.

I'm on the fence about this---I do want to get rid of cc.gcc but it's a bit disingenous unless we can somehow filter the other libraries out. Maybe we can leave that for a follow-up PR?

#91293 got rid of cc.gcc here.

pkgs/build-support/cc-wrapper/add-flags.sh

matthewbauer · 2020-04-14T21:53:15Z

Does that change here? I would expect this to still only include it for clang++. Come to think of it, wouldn't CC=$CXX be a nicer fix for those cases or does that not work?

Yeah, you're right - I was forgetting what the issue was there. We still need CXX to be used.

Ericson2314 · 2020-04-20T05:23:34Z

OK with the last push I have both stdenvs building, so now we can clean up in earnest.

Mic92 · 2020-04-20T09:13:39Z

We also have some tools that consume the c/c++ standard includes: cquery, clang-tools and ccls

Mic92 · 2020-06-22T06:59:58Z

We also have some tools that consume the c/c++ standard includes: cquery, clang-tools and ccls

As it turns out those are not affected by this change. I removed cquery last week. Clangd and CCLS only take the libcxx include path as input. I remember to use default_cxx_stdlib_compile for youcompletme at some point, but this was more of a hack and using something like ${llvmPackages.libcxx}/include/c++/v1 would be cleaner.

Ericson2314 · 2020-06-22T14:38:28Z

OK, it evals! I don't think we need any more back-compat stuff ATM, but happy to add things in requested.

NIX_CXXSTDLIB_COMPILE has been removed in NixOS#85189 and NixOS#85189 (comment) remommends using the files in ${clang}/nix-support to find the correct flags to pass to libclang.

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Ericson2314 mentioned this pull request Apr 17, 2020

treewide: Get rid of -dumpmachine in favor of static info #85468

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Ericson2314 force-pushed the cxx-wrapper-debt branch 2 times, most recently from a7808ca to 995989a Compare April 19, 2020 01:25

ofborg bot added the 6.topic: stdenv Standard environment label Apr 19, 2020

Ericson2314 force-pushed the cxx-wrapper-debt branch from 995989a to 604b60d Compare April 19, 2020 04:01

Ericson2314 changed the title ~~C/C++ compilers: Be sane with standard libraries~~ C++ compilers: Be sane with standard libraries Apr 19, 2020

Ericson2314 force-pushed the cxx-wrapper-debt branch from 604b60d to a385085 Compare June 14, 2020 21:44

Ericson2314 changed the base branch from master to staging June 14, 2020 21:44

emscripten: Don't always clain to have a GCC

e00d4d6

Ericson2314 force-pushed the cxx-wrapper-debt branch 2 times, most recently from eba5f1f to 9e62a88 Compare June 22, 2020 04:21

Ericson2314 marked this pull request as ready for review June 22, 2020 04:22

Ericson2314 requested a review from jonringer as a code owner June 22, 2020 04:22

C++ Compilers: Systematize handling of standard libraries

f3f7612

Ericson2314 force-pushed the cxx-wrapper-debt branch from 9e62a88 to f3f7612 Compare June 22, 2020 04:24

Ericson2314 merged commit fa54dd3 into NixOS:staging Jun 22, 2020

Ericson2314 deleted the cxx-wrapper-debt branch June 22, 2020 14:38

vcunat mentioned this pull request Jun 29, 2020

nss: 3.52.1 -> 3.54 #91746

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alyssais mentioned this pull request Jun 30, 2020

rustc: 1.43.0 -> 1.44.1 #89576

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DieGoldeneEnte mentioned this pull request Jul 2, 2020

[wait for staging] remove libstdcxxHook, since it isn't needed anymore nixos-rocm/nixos-rocm#45

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symphorien mentioned this pull request Feb 3, 2022

rust-bindgen: fix finding c++ stdlib #158041

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rrbutani added the 6.topic: llvm/clang Issues related to llvmPackages, clangStdenv and related label May 27, 2024

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Motivation for this change

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Ericson2314 commented Apr 14, 2020

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Mic92 Jun 15, 2020 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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matthewbauer Apr 14, 2020 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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matthewbauer Apr 14, 2020 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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matthewbauer commented Apr 14, 2020

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LnL7 commented Apr 14, 2020

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LnL7 Apr 15, 2020 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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matthewbauer commented Apr 14, 2020

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Ericson2314 commented Apr 20, 2020

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Mic92 commented Apr 20, 2020

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Mic92 commented Jun 22, 2020

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Ericson2314 commented Jun 22, 2020

Ericson2314 commented Apr 14, 2020 •

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