build-support/cc-wrapper: pass in non-existent --sysroot= to untangle… by trofi · Pull Request #210004 · NixOS/nixpkgs

trofi · 2023-01-10T07:57:00Z

… from libc

I would like to add an extra gcc build step during linux bootstrap (#208412). This makes it early bootstrap compiler linked and targeted against bootstrapTools glibc including it's headers.

Without this change gcc's spec files always prefer bootstrapTools glibc for header search path (passed in as --with-native-system-header-dir=). We'can't override it with:

-I option as it gets stacked before gcc-specific headers, we need to keep glibc headers after gcc as gcc cleans namespace up for C standard by using #include_next and by undefining system macros.
-idirafter option as it gets appended after existing glibc-includes

This --sysroot=/nix/store/does/not/exist hack allows us to remove existing glibc headers and add new ones with -idirafter.

We use cc-cflags-before instead of libc-cflags to allow user to define their own --sysroot= (like firefox does).

To keep it working prerequisite cross-symlink in gcc.libs is required: #209153

Description of changes

Things done

… from libc I would like to add an extra `gcc` build step during linux bootstrap (NixOS#208412). This makes it early bootstrap compiler linked and targeted against `bootstrapTools` `glibc` including it's headers. Without this change `gcc`'s spec files always prefer `bootstrapTools` `glibc` for header search path (passed in as --with-native-system-header-dir=). We'can't override it with: - `-I` option as it gets stacked before gcc-specific headers, we need to keep glibc headers after gcc as gcc cleans namespace up for C standard by using #include_next and by undefining system macros. - `-idirafter` option as it gets appended after existing `glibc`-includes This `--sysroot=/nix/store/does/not/exist` hack allows us to remove existing `glibc` headers and add new ones with `-idirafter`. We use `cc-cflags-before` instead of `libc-cflags` to allow user to define their own `--sysroot=` (like `firefox` does). To keep it working prerequisite cross-symlink in gcc.libs is required: NixOS#209153

mweinelt · 2023-01-26T23:41:05Z

This commit broke uboot packages on staging-next. See https://hydra.nixos.org/eval/1789657?filter=uboot&compare=1789649.

8c80bd08b7e39229947d55104d1871f5066437d9 is the first bad commit
commit 8c80bd08b7e39229947d55104d1871f5066437d9
Author: Sergei Trofimovich <slyich@gmail.com>
Date:   Tue Jan 10 07:43:51 2023 +0000

    build-support/cc-wrapper: pass in non-existent --sysroot= to untangle from libc
    
    I would like to add an extra `gcc` build step during linux bootstrap
    (https://github.com/NixOS/nixpkgs/issues/208412). This makes it early
    bootstrap compiler linked and targeted against `bootstrapTools` `glibc`
    including it's headers.
    
    Without this change `gcc`'s spec files always prefer `bootstrapTools` `glibc`
    for header search path (passed in as --with-native-system-header-dir=). We'can't
    override it with:
    
    - `-I` option as it gets stacked before gcc-specific headers, we need to keep
      glibc headers after gcc as gcc cleans namespace up for C standard by using
      #include_next and by undefining system macros.
    - `-idirafter` option as it gets appended after existing `glibc`-includes
    
    This `--sysroot=/nix/store/does/not/exist` hack allows us to remove existing
    `glibc` headers and add new ones with `-idirafter`.
    
    We use `cc-cflags-before` instead of `libc-cflags` to allow user to define
    their own `--sysroot=` (like `firefox` does).
    
    To keep it working prerequisite cross-symlink in gcc.libs is required:
    https://github.com/NixOS/nixpkgs/pull/209153

 pkgs/build-support/cc-wrapper/default.nix | 7 +++++++
 1 file changed, 7 insertions(+)

trofi · 2023-01-26T23:47:02Z

Sounds plausible. The failure is not outright obvious:

  HOSTCC  tools/bmp_logo
  HOSTCC  tools/gdb/gdbsend.o
In file included from ././include/compiler.h:23,
                 from <command-line>:
include/errno.h:28:22: error: missing binary operator before token "("
   28 | #if CONFIG_IS_ENABLED(ERRNO_STR)
      |                      ^
In file included from include/stdlib.h:9,
                 from ././include/compiler.h:24,
                 from <command-line>:
include/malloc.h:886:22: error: missing binary operator before token "("
  886 | #if CONFIG_IS_ENABLED(SYS_MALLOC_SIMPLE)
      |                      ^
include/malloc.h:984:8: error: unknown type name 'ulong'
  984 | extern ulong mem_malloc_start;
      |        ^~~~~

Looking.

trofi · 2023-01-27T00:21:42Z

yeah, include order did change and broke #include_next.

On FHS systems include order is:

 /usr/lib/gcc/x86_64-pc-linux-gnu/12/include
 /usr/lib/gcc/x86_64-pc-linux-gnu/12/include-fixed
 /usr/include
 include
 ./arch/sandbox/include

(libc includes come before -idirafter ones)

On staging-next:

 /run/current-system/sw/include
 /nix/store/g7z994p16v096ryq0ic1jmgywcylhq40-ncurses-6.4-dev/include
 /nix/store/7ksr2nxylzg7ni895vhyw7ia2qbg2c9d-dtc-1.6.1/include
 /nix/store/76c2420qdy7gg4pdvspvsafxnpwp1qm1-flex-2.6.4/include
 /nix/store/7pg5j6k1m9y2bn2hr05j0v4nasq23xmr-openssl-3.0.7-dev/include
 /nix/store/m0kcrs788zwc6mp3qalfdyzlkw999dhm-python3-3.10.9-env/include
 /nix/store/l68yk5n1nz6qxck1f0b4zbcmbcvi8px8-util-linux-minimal-2.38.1-dev/include
 /nix/store/bycbddw4j1nkf3nipwi0qlkpfh0h2z5w-gnutls-3.7.8-dev/include
 /nix/store/ain09ii77w4c006y2y1852g36mva7haa-nettle-3.8.1-dev/include
 /nix/store/4j2zssk8nq7alxhqpna9ps6hxz0fmi8m-gmp-with-cxx-6.2.1-dev/include
 /nix/store/v1nxrwb4ls09sbbrwlkgxs7dlw8paksh-gcc-11.3.0/lib/gcc/x86_64-unknown-linux-gnu/11.3.0/include
 /nix/store/v1nxrwb4ls09sbbrwlkgxs7dlw8paksh-gcc-11.3.0/include
 /nix/store/v1nxrwb4ls09sbbrwlkgxs7dlw8paksh-gcc-11.3.0/lib/gcc/x86_64-unknown-linux-gnu/11.3.0/include-fixed
 include
 ./arch/sandbox/include
 /nix/store/nasgvbblxi25r6y1s82il4m0m4ghib68-glibc-2.35-224-dev/include

(libc includes come after -idirafter ones).

Should be easy to workaround just for u-boot. I'll propose u-boot specific fix tomorrow morning.

trofi · 2023-01-27T08:08:49Z

Proposed possible -idirafter workaround for staging-next as #212919

`ubootTools` build broke after NixOS#210004 where we started dropping default libc include path and switched to `-idirafter` way of specifying libc headers. Unfortunately the way it's implemented it injects -idirafter after user's flags, not before. That allows users to inject their paths before libc include paths, not after (as it would notmally happen). The change works it around for u-boot by pulling -idirafter libc flags before user's flags.

vcunat · 2023-01-27T16:43:56Z

Also rmlint build got broken by this: https://hydra.nixos.org/build/206664410
(I wasn't sure so I built it on current staging-next with just this commit reverted.)
And there are several other regressed builds with similarly looking linker errors.

EDIT: also confirmed for packages: usbmuxd2, dmd, godot.

trofi · 2023-01-27T17:26:40Z

rmlint exposes something that look like a glib underlinking bug (and the fix will likely be in glib). If glib rebuild is already big we can revert this change and take the full hit of rebuilding everything again.

Will have a more detailed look in 1-2 hours to see how I broke glib / rmlint.

trofi · 2023-01-27T17:58:19Z

False alarm. glib looks fine at least from underlinking standpoint. It's something related to rmlint's handling of CFLAGS/LDFLAGS. Still looking.

trofi · 2023-01-27T19:12:09Z

Proposed rmlint fix as:

: rmlint: fix NIX_* environment propagations to scons #213003. I would say it's a genuine bug in too eager environment filtering.

Looking at usbmuxd2.

trofi · 2023-01-27T19:34:44Z

usbmuxd2 exposed the fact that our gcc's lib lacks libstdc++fs.la:

$ find $(nix-build --no-link -A stdenv.cc.cc.lib) | fgrep libstdc | unnix

/<<NIX>>/gcc-11.3.0-lib/lib/libstdc++fs.la

/<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.la
/<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.so.6.0.29
/<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.so
/<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.so.6

Note: libstdc++fs.la is alone here.

It was forgotten in non-lib output:

$ find $(nix-build --no-link -A stdenv.cc.cc) | fgrep libstdc | unnix
/<<NIX>>/gcc-11.3.0/lib/libstdc++.a
/<<NIX>>/gcc-11.3.0/lib/libstdc++fs.a

I'll think of a local clangStdenv workaround (or a fix). Only 20 packages seem to use it, might not be too large to rebuild.

trofi · 2023-01-27T21:37:51Z

Proposed usbmuxd2 fix as:

: build-support/cc-wrapper: add libstdc++fs into default library path for clang #213021

Looking at godot.

trofi · 2023-01-27T22:04:39Z

Proposed godot change as:

: godot: fix NIX_* environment propagations to scons #213030

Looking at dmd.

trofi · 2023-01-27T22:48:13Z

More fallout:

d-seams, llvmPackages_rocm.compiler-rt: build-support/cc-wrapper: add libstdc++fs into default library path for clang #213021
dmd: dmd: set --sysroot=/ to avoid cc-wrapper value #213141
fluxus: fluxus: fix NIX_* environment propagations to scons #213160
godot-export-templates: (fixed with godot?)
ipxe: ipxe: fix build by fixing -idirafter ordering #213106
rhvoice: rhvoice: fix NIX_* environment propagations to scons #213117
wimboot: wimboot: fix build by fixing -idirafter ordering #213108

…or clang After NixOS#210004 `usbmuxd2` started failing to build as: usbmuxd2-unstable> .../ld: cannot find -lstdc++fs: No such file or directory usbmuxd2-unstable> clang-11: error: linker command failed with exit code 1 (use -v to see invocation) This started happening because NixOS#210004 exposed a long-standing bug in `gcc` derivation: `cc.lib` is missing `libstdc++fs` library: $ find $(nix-build --no-link -A stdenv.cc.cc.lib) | fgrep libstdc | unnix /<<NIX>>/gcc-11.3.0-lib/lib/libstdc++fs.la /<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.la /<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.so.6.0.29 /<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.so /<<NIX>>/gcc-11.3.0-lib/lib/libstdc++.so.6 It was not moved from `cc.out` output: $ find $(nix-build --no-link -A stdenv.cc.cc) | fgrep libstdc | unnix /<<NIX>>/gcc-11.3.0/lib/libstdc++.a /<<NIX>>/gcc-11.3.0/lib/libstdc++fs.a This change adds `cc` library lookup path back to `staging-next` until `gcc` is fixed.`

`ipxe` build broke after NixOS#210004 where we started dropping default libc include path and switched to `-idirafter` way of specifying libc headers. Unfortunately the way it's implemented it injects `-idirafter` after user's flags, not before. That allows users to inject their paths before libc include paths, not after (as it would notmally happen). The change works it around for `ipxe` by pulling `-idirafter` libc flags before user's flags.

`wimboot` build broke after NixOS#210004 where we started dropping default libc include path and switched to `-idirafter` way of specifying libc headers. Unfortunately the way it's implemented it injects `-idirafter` after user's flags, not before. That allows users to inject their paths before libc include paths, not after (as it would notmally happen). The change works it around for `wimboot` by pulling `-idirafter` libc flags before user's flags.

After NixOS#210004 `dmd` started failing build as: ld: warning: libm.so.6, needed by ./generated/linux/release/64/lib.so, not found (try using -rpath or -rpath-link) ld: /build/druntime/generated/linux/release/64/libdruntime.so: undefined reference to `log10@GLIBC_2.2.5' This happens because --sysroot=/nix/store/does/not/exist removes not just include headers by prefixing wrong path, but also removes RUNPATH dependencies of linked libraries. It's an unintended effect. Restore the build by reversing the effect with --sysroot=/.

trofi · 2023-01-28T16:41:05Z

On top of the above fixes for staging-next proposed full revert against staging: #213185 .

There are too many subtle changes that need to be handled one by one: library search paths, include search path order, bootstrap overrides and sequencing. --sysroot= is too blunt for it.

…untangle from libc" This reverts commit 8c80bd0 ("build-support/cc-wrapper: pass in non-existent --sysroot= to untangle from libc"). This change was good in spirit: we caught a few genuine problems with `scons` based packages (`godot`, `fluxus`) and unexpected `-idirafter` includes in various boot loadres (`ipxe`, wimboot`): NixOS#210004 (comment) Unfortunately `--sysroot=` also has a negative impact on libary search order for DT_NEEDED libraries and RUNPATHs of linked libraries. This unexpectedly broke `dmd`, `d-seams`, `llvmPackages_rocm.compiler-rt`). An interesting case of unexpected breakage is `usbmuxd2` where the bug exposed incomplete library move on `libstdc++fs` in `gcc`. The library breakage is very non-intuitive (on top of already unusual layout of `cc-wrapper` driver). Let's revert this change for now. Once it lands we can undo `--sysroot=/` workarounds merged for `staging-next`.

ghost · 2023-01-31T08:00:13Z

cc-wrapper: conditionalize the nonexistent sysroot hack #213738

After NixOS/nixpkgs#210004 `dmd` started failing build as: ld: warning: libm.so.6, needed by ./generated/linux/release/64/lib.so, not found (try using -rpath or -rpath-link) ld: /build/druntime/generated/linux/release/64/libdruntime.so: undefined reference to `log10@GLIBC_2.2.5' This happens because --sysroot=/nix/store/does/not/exist removes not just include headers by prefixing wrong path, but also removes RUNPATH dependencies of linked libraries. It's an unintended effect. Restore the build by reversing the effect with --sysroot=/.

@Ericson2314

#### Summary By default, when you type `make`, GCC will compile itself three times. This PR inhibits that behavior by configuring GCC with `--disable-bootstrap`, and reimplements the triple-rebuild using Nix rather than `make`/`sh`. #### Immediate Benefits - Allow `gcc11` and `gcc12` on `aarch64` (without needing new `bootstrapFiles`) - Faster stdenv rebuilds: the third compilation of gcc (i.e. stageCompare) is no longer a `drvInput` of the final stdenv. This allows Nix to build stageCompare in parallel with the rest of nixpkgs instead of in series. - No more copying `libgcc_s` out of the bootstrap-files or other derivations - No more Frankenstein compiler: the final gcc and the libraries it links against (mpfr, mpc, isl, glibc) are all built by the same compiler (xgcc) instead of a mixture of the bootstrapFiles' compiler and xgcc. - No more [static lib{mpfr,mpc,gmp,isl}.a hack] - Many other small `stdenv` hacks eliminated - `gcc` and `clang` share the same codepath for more of `cc-wrapper`. #### Future Benefits - This should allow using a [foreign] `bootstrap-files` so long as `hostPlatform.canExecute bootstrapFiles`. - This should allow each of the libraries that ship with `gcc` (lib{backtrace, atomic, cc1, decnumber, ffi, gomp, iberty, offloadatomic, quadmath, sanitizer, ssp, stdc++-v3, vtv}) to be built in separate (one-liner) derivations which `inherit src;` from `gcc`, much like NixOS/nixpkgs#132343 #### Incorporates - NixOS/nixpkgs#210004 - NixOS/nixpkgs#36948 (unreverted) - NixOS/nixpkgs#210325 - NixOS/nixpkgs#210118 - NixOS/nixpkgs#210132 - NixOS/nixpkgs#210109 - NixOS/nixpkgs#213909 - NixOS/nixpkgs#216136 - NixOS/nixpkgs#216237 - NixOS/nixpkgs#210019 - NixOS/nixpkgs#216232 - NixOS/nixpkgs#216016 - NixOS/nixpkgs#217977 - NixOS/nixpkgs#217995 #### Closes - Closes #108305 - Closes #108111 - Closes #201254 - Closes #208412 #### Credits This project was made possible by three important insights, none of which were mine: 1. @Ericson2314 was the first to advocate for this change, and probably the first to appreciate its advantages. Nix-driven (external) bootstrap is "cross by default". 2. @trofi has figured out a lot about how to get gcc to not mix up the copy of `libstdc++` that it depends on with the copy that it builds, by moving the `bootstrapFiles`' `libstdc++` into a [versioned directory]. This allows a Nix-driven bootstrap of gcc without the final gcc would still having references to the `bootstrapFiles`. 3. Using the undocumented variable [`user-defined-trusted-dirs`] when building glibc. When glibc `dlopen()`s `libgcc_s.so`, it uses a completely different and totally special set of rules for finding `libgcc_s.so`. This trick is the only way we can put `libgcc_s.so` in its own separate outpath without creating circular dependencies or dependencies on the bootstrapFiles. I would never have guessed to use this (or that it existed!) if it were not for a [comment in guix] which @Mic92 [mentioned]. My own role in this PR was basically: being available to go on a coding binge at an opportune moment, so we wouldn't waste a [crisis]. [aarch64-compare-ofborg]: https://github.com/NixOS/nixpkgs/pull/209870/checks?check_run_id=10662822938 [amd64-compare-ofborg]: https://github.com/NixOS/nixpkgs/pull/209870/checks?check_run_id=10662825857 [nonexistent sysroot]: NixOS/nixpkgs#210004 [versioned directory]: NixOS/nixpkgs#209054 [`user-defined-trusted-dirs`]: https://sourceware.org/legacy-ml/libc-help/2013-11/msg00026.html [comment in guix]: https://github.com/guix-mirror/guix/blob/5e4ec8218142eee8e6e148e787381a5ef891c5b1/gnu/packages/gcc.scm#L253 [mentioned]: NixOS/nixpkgs#210112 (comment) [crisis]: NixOS/nixpkgs#108305 [foreign]: NixOS/nixpkgs#170857 (comment) [static lib{mpfr,mpc,gmp,isl}.a hack]: https://github.com/NixOS/nixpkgs/blob/2f1948af9c984ebb82dfd618e67dc949755823e2/pkgs/stdenv/linux/default.nix#L380

trofi requested a review from Ericson2314 as a code owner January 10, 2023 07:57

This was referenced Jan 10, 2023

Bootstrap Reform and aarch64-linux's GCC Upgrade #208412

Closed

stdenv: Nix-driven bootstrap of gcc #209870

Merged

stdenv/linux/default.nix: add gcc rebuild during bootstrap #209063

Closed

ghost approved these changes Jan 11, 2023

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trofi merged commit 67a3a14 into NixOS:staging Jan 14, 2023

trofi deleted the cc-fake-sysroot branch January 14, 2023 08:18

mweinelt mentioned this pull request Jan 26, 2023

staging-next 2023-01-21 #211923

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trofi mentioned this pull request Jan 27, 2023

ubootTools: fix build by fixing -idirafter ordering #212919

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trofi mentioned this pull request Jan 27, 2023

build-support/cc-wrapper: add libstdc++fs into default library path for clang #213021

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trofi mentioned this pull request Jan 28, 2023

ipxe: fix build by fixing -idirafter ordering #213106

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trofi mentioned this pull request Jan 28, 2023

wimboot: fix build by fixing -idirafter ordering #213108

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trofi mentioned this pull request Jan 28, 2023

dmd: set --sysroot=/ to avoid cc-wrapper value #213141

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trofi mentioned this pull request Feb 17, 2023

godot: fix NIX_* environment propagations to scons #213030

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rrbutani added the 6.topic: stdenv Standard environment label May 27, 2024

beviu mentioned this pull request Nov 6, 2025

clang: include dir / idirafter ordering confusion #442465

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