linux/bootstrap-tools: move libstdc++ out of default library search path #209054
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This change allows building new gcc during bootstrap without fear of
pulling in outdated libstdc++.so after g++ switched from bootstrapTools
to freshly built g++.
Noticed when tried to add early bootstrap stage to rebuild `gcc` before
`glibc` is fully untangled from `bootstrapTools` as a failure to built
`binutils`:
ld: dwp.o: in function `__gnu_cxx::new_allocator<gold::Dwp_output_file::Contribution>::allocate(unsigned long, void const*)':
/nix/store/...-gcc-11.3.0/include/c++/11.3.0/ext/new_allocator.h:116: undefined reference to `std::__throw_bad_array_new_length()'
The change survives existing bootstrap and unblockes early `gcc` bootstrap.
ghost
approved these changes
Jan 9, 2023
| @@ -17,6 +17,15 @@ else | |||
| LD_BINARY=$out/lib/ld-*so.? | |||
| fi | |||
|
|
|||
| # path to version-specific libraries, like libstdc++.so | |||
| LIBSTDCXX_SO_DIR=$(echo $out/lib/gcc/*/*) | |||
There was a problem hiding this comment.
I checked that for all 16 of our existing bootstrap-files tarballs there is only one subdirectory under lib/gcc, and only one subdirectory beneath that (unpack-bootstrap-tools.sh is a huge pain because every time we touch it we have to rebuild the whole universe).
ghost
mentioned this pull request
|
This regressed tests for bootstrap tarball building: I think it's a pure test issue. Test does not use any wrappers and assumes certain directory layout. Looking. |
trofi
added a commit
to trofi/nixpkgs
that referenced
this pull request
Jan 14, 2023
After NixOS#209054 we started moving libstdc++.so out of default glibc's paths. This exposed bootstrap tools build failure as: $ nix build --no-link -f ./pkgs/stdenv/linux/make-bootstrap-tools.nix ... > .../bin/bar: error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory Note that bootstrap itself did not break. The change only expands handcrafted `-rpath` entries.
13 tasks
|
Proposed the fix as #210752 |
wegank
pushed a commit
to wegank/nixpkgs
that referenced
this pull request
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 pull request
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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This change allows building new gcc during bootstrap without fear of pulling in outdated libstdc++.so after g++ switched from bootstrapTools to freshly built g++.
Noticed when tried to add early bootstrap stage to rebuild
gccbeforeglibcis fully untangled frombootstrapToolsas a failure to builtbinutils:The change survives existing bootstrap and unblockes early
gccbootstrap.Description of changes
Things done
sandbox = trueset innix.conf? (See Nix manual)nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage./result/bin/)nixos/doc/manual/md-to-db.shto update generated release notes