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fix(buck2): allow rustc to use Nix environment when compiling #2266

Merged
merged 1 commit into from
May 31, 2023
Merged

fix(buck2): allow rustc to use Nix environment when compiling #2266

merged 1 commit into from
May 31, 2023

Commits on May 31, 2023

  1. fix(buck2): allow rustc to use Nix environment when compiling 

    This change enables our project to build using the Nix environment
running on Linux and macOS platforms.

Background
----------

The upstream `rustc_action.py` script which invokes `rustc` filters the
environment in an effort to maintain a better sandboxed build. When we
build in a Nix environment (currently used for development and shortly
in CI), there are several environment variables that cause the correct
linking behavior under Nix.

The Nix environment provides wrapper scripts for `clang` and `clang++`
which use these environment variables. The `rustc` program is
responsible for invoking the linker (by default this tends to be
`cc`/`clang`) which means these environment variables need to be present
in the `rustc` process so that its children can inherit them.

The Fix
-------

While there were many attempts at a solution to this problem, we went
with a "patch the upstream" approach. In other words, the
`rustc_action.py` script is what prevents our correct Nix behavior, so
we slightly augmented it with support for more environment variables.
This script is provided to us via the upstream
`facebookincubator/buck2-prelude` Git repository which we currently
vendor using `git subtree`. This means that our "patch" will be wiped
out when we re-vendor/update against upstream changes. With this in
mind, we provide a `third-party/patches/nix_rustc_action.patch` file
which should allow us to patch over upstream updates similar to upstream
patching in a packaging system.

Co-authored-by: Nick Gerace <[email protected]>
Signed-off-by: Fletcher Nichol <[email protected]>
    @fnichol @nickgerace
    fnichol and nickgerace committed May 31, 2023
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