diff options
author | Adam Joseph <adam@westernsemico.com> | 2023-02-23 21:32:36 -0800 |
---|---|---|
committer | Adam Joseph <adam@westernsemico.com> | 2023-04-02 13:49:41 -0700 |
commit | 7553d0fe29801938bcb280bb324b579ef9016aea (patch) | |
tree | 0e0073ae6d9a5bc8935b9a30adaeba883ca510d7 /pkgs/build-support/cc-wrapper | |
parent | fdd49f1bcd8a7f0b5e29f550d698b2abe5c540cd (diff) |
stdenv: Nix-driven bootstrap of gcc
#### 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 https://github.com/NixOS/nixpkgs/pull/132343 #### Incorporates - https://github.com/NixOS/nixpkgs/pull/210004 - https://github.com/NixOS/nixpkgs/pull/36948 (unreverted) - https://github.com/NixOS/nixpkgs/pull/210325 - https://github.com/NixOS/nixpkgs/pull/210118 - https://github.com/NixOS/nixpkgs/pull/210132 - https://github.com/NixOS/nixpkgs/pull/210109 - https://github.com/NixOS/nixpkgs/pull/213909 - https://github.com/NixOS/nixpkgs/pull/216136 - https://github.com/NixOS/nixpkgs/pull/216237 - https://github.com/NixOS/nixpkgs/pull/210019 - https://github.com/NixOS/nixpkgs/pull/216232 - https://github.com/NixOS/nixpkgs/pull/216016 - https://github.com/NixOS/nixpkgs/pull/217977 - https://github.com/NixOS/nixpkgs/pull/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]: https://github.com/NixOS/nixpkgs/pull/210004 [versioned directory]: https://github.com/NixOS/nixpkgs/pull/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]: https://github.com/NixOS/nixpkgs/pull/210112#issuecomment-1379608483 [crisis]: https://github.com/NixOS/nixpkgs/issues/108305 [foreign]: https://github.com/NixOS/nixpkgs/pull/170857#issuecomment-1170558348 [static lib{mpfr,mpc,gmp,isl}.a hack]: https://github.com/NixOS/nixpkgs/blob/2f1948af9c984ebb82dfd618e67dc949755823e2/pkgs/stdenv/linux/default.nix#L380
Diffstat (limited to 'pkgs/build-support/cc-wrapper')
-rw-r--r-- | pkgs/build-support/cc-wrapper/default.nix | 35 |
1 files changed, 33 insertions, 2 deletions
diff --git a/pkgs/build-support/cc-wrapper/default.nix b/pkgs/build-support/cc-wrapper/default.nix index f6fb7bd001cd0..25481fec664da 100644 --- a/pkgs/build-support/cc-wrapper/default.nix +++ b/pkgs/build-support/cc-wrapper/default.nix @@ -17,9 +17,40 @@ , isGNU ? false, isClang ? cc.isClang or false, gnugrep ? null , buildPackages ? {} , libcxx ? null + +# Whether or not to add `-B` and `-L` to `nix-support/cc-{c,ld}flags` +, useCcForLibs ? + + # Always add these flags for Clang, because in order to compile (most + # software) it needs libraries that are shipped and compiled with gcc. + if isClang then true + + # Never add these flags for a build!=host cross-compiler or a host!=target + # ("cross-built-native") compiler; currently nixpkgs has a special build + # path for these (`crossStageStatic`). Hopefully at some point that build + # path will be merged with this one and this conditional will be removed. + else if (with stdenvNoCC; buildPlatform != hostPlatform || hostPlatform != targetPlatform) then false + + # Never add these flags when wrapping the bootstrapFiles' compiler; it has a + # /usr/-like layout with everything smashed into a single outpath, so it has + # no trouble finding its own libraries. + else if (cc.passthru.isFromBootstrapFiles or false) then false + + # Add these flags when wrapping `xgcc` (the first compiler that nixpkgs builds) + else if (cc.passthru.isXgcc or false) then true + + # Add these flags when wrapping `stdenv.cc` + else if (cc.stdenv.cc.cc.passthru.isXgcc or false) then true + + # Do not add these flags in any other situation. This is `false` mainly to + # prevent these flags from being added when wrapping *old* versions of gcc + # (e.g. `gcc6Stdenv`), since they will cause the old gcc to get `-B` and + # `-L` flags pointing at the new gcc's libstdc++ headers. Example failure: + # https://hydra.nixos.org/build/213125495 + else false + +# the derivation at which the `-B` and `-L` flags added by `useCcForLibs` will point , gccForLibs ? if useCcForLibs then cc else null -# same as `gccForLibs`, but generalized beyond clang -, useCcForLibs ? isClang }: with lib; |