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aarch64 build failures with gcc 10 and binutils 2.34 #108111

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FRidh opened this issue Jan 1, 2021 · 1 comment · Fixed by #209870
Closed

aarch64 build failures with gcc 10 and binutils 2.34 #108111

FRidh opened this issue Jan 1, 2021 · 1 comment · Fixed by #209870

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@FRidh
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FRidh commented Jan 1, 2021

Describe the bug
#89793 (comment)

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Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

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# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:
FRidh added a commit to FRidh/nixpkgs that referenced this issue Jan 2, 2021
Several aarch64 builds fail with is referenced by DSO followed by
bin/ld: final link failed: bad value. This seems related to libgcc_s.so.

NixOS#108111
FRidh added a commit that referenced this issue Jan 2, 2021
Several aarch64 builds fail with is referenced by DSO followed by
bin/ld: final link failed: bad value. This seems related to libgcc_s.so.

#108111
@FRidh FRidh changed the title aarch64 build failures with gcc 10 and binutils 2.34 (staging-next) aarch64 build failures with gcc 10 and binutils 2.34 Jan 3, 2021
@FRidh
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FRidh commented Jan 3, 2021

Using gcc 9 for now with aarch64.
#108305 (duplicate)

@FRidh FRidh added this to the 21.03 milestone Jan 3, 2021
@FRidh FRidh closed this as completed Jan 4, 2021
wegank pushed a commit to wegank/nixpkgs that referenced this issue Feb 1, 2023
#### Immediate Benefits

- Allow `gcc11` on `aarch64`
- No more copying `libgcc_s` out of the bootstrap-files or other
  derivations
- No more [static `lib{mpfr,mpc,gmp,isl}.a`
  hack](https://github.com/NixOS/nixpkgs/blob/2f1948af9c984ebb82dfd618e67dc949755823e2/pkgs/stdenv/linux/default.nix#L380)
- *Zero* additional `gcc` builds (stage1+stage2+stageCompare)
  - The `gcc` derivation builds `gcc` once instead of three times.
  - The libraries that are linked into the final `pkgs.gcc` (`mpfr`,
    `mpc`, `gmp`, `isl`, `glibc`) are built by
    `stdenv.__bootPkgs.gcc` rather than by the `bootstrapFiles`.  No
    more Frankenstein compiler!
  - stageCompare runs **concurrently** with (not in series with)
    with `stdenv`'s dependees.
- Many other `stdenv` hacks eliminated.
  - `gcc` and `clang` share the same codepath for more of
    `cc-wrapper`.
  - Makes the cross and native codepaths much more similar --
    another step towards "cross by default".

Note that *all* the changes in this PR are controlled by flags; no
old codepaths need to be removed until/if we're completely certain
that this is the right way to go.

#### Future Benefits

- This should allow using a [foreign] `bootstrap-files` so long as
  `hostPlatform.canExecute bootstrapFiles`.
- There will be an "avalanche of simplification" when we set
  `enableGccExternalBootstrap=true` and run dead code elimination.
  It's really quite a huge amount of code that goes away.
  Native-gcc has its own special codepath in so many places, while
  cross-gcc and clang work the same way (and are much simpler).
- 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`.
  - Building `libstdc++-v3` in a separate derivation will eliminate
    a lot of accidental-reference-to-the-`bootstrapFiles` landmines.

#### Incorporates

- NixOS#209054
- NixOS#210004
- NixOS#36948 (unreverted)
- NixOS#210325
- NixOS#210118
- NixOS#210132
- NixOS#210109

#### Closes

- Closes NixOS#208412
- Closes NixOS#108111
- Closes NixOS#108305
- Closes NixOS#201254

#### Build history

- First successful builds (stage1/stage2):
  - powerpc64le-linux at 9c7e9ef
  - x86_64-linux at 9c7e9ef
  - aarch64-linux at 4d5bc7d

- First successful comparisons (stageCompare):
  - at 81949cf
  - [aarch64-linux][aarch64-compare-ofborg]
  - [x86\_64-linux][amd64-compare-ofborg]

#### 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.  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.  Now that gcc is written in C++, it depends on
   `libstdc++`, builds a copy of `libstdc++`, and builds auxiliary
   products (like `libplugin`) which depend on `libstdc++`.  @trofi
   developed two important techniques for keeping this straight: the
   use of a [nonexistent sysroot] and moving the `bootstrapFiles`'
   `libstdc++` into a [versioned directory].  Without these two
   discoveries, external bootstrap would be impossible, because the
   final gcc would still have 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#210004
[versioned directory]: NixOS#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#210112 (comment)
[crisis]: NixOS#108305
[foreign]: NixOS#170857 (comment)
tm-drtina pushed a commit to awakesecurity/nixpkgs that referenced this issue Apr 27, 2024
 #### 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#132343

 #### Incorporates

- NixOS#210004
- NixOS#36948 (unreverted)
- NixOS#210325
- NixOS#210118
- NixOS#210132
- NixOS#210109
- NixOS#213909
- NixOS#216136
- NixOS#216237
- NixOS#210019
- NixOS#216232
- NixOS#216016
- NixOS#217977
- NixOS#217995

 #### Closes

- Closes NixOS#108305
- Closes NixOS#108111
- Closes NixOS#201254
- Closes NixOS#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#210004
[versioned directory]: NixOS#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#210112 (comment)
[crisis]: NixOS#108305
[foreign]: NixOS#170857 (comment)
[static lib{mpfr,mpc,gmp,isl}.a hack]: https://github.com/NixOS/nixpkgs/blob/2f1948af9c984ebb82dfd618e67dc949755823e2/pkgs/stdenv/linux/default.nix#L380
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