Set CXX and AR environment variables for cross-compilation#997
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Set CXX and AR environment variables for cross-compilation#997colincasey wants to merge 1 commit into
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Also set the CXX_* and AR_* environment variables (in addition to the existing CC_* and CARGO_TARGET_*_LINKER) when configuring cross-compilation toolchains. This ensures crates that use CMake or the cc crate to build C++ code (such as aws-lc-sys) find the correct cross-compiler. Refactors the match arms to store a toolchain prefix and derive all tool binary names from it via format!(). Fixes #725
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Apr 9, 2026
Adds a workflow that cross-compiles the buildpack for both x86_64 and aarch64 using libcnb-cargo from the cross-compile-cxx-ar-env-vars branch which sets CXX_* and AR_* env vars during cross-compilation. Also switches libcnb/libcnb-test deps to git dependencies on the same branch to ensure consistent builds.
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Summary
cross_compile_assistance()to store a toolchain prefix per platform case and derivegcc,g++, andarbinary names viaformat!CXX_*andAR_*environment variables alongside existingCC_*andCARGO_TARGET_*_LINKERfor cross-compilationcccrate for C++ code (such asaws-lc-sys) find the correct cross-compiler toolchainContext
The cross-compile toolchain docs recommend setting
CC,CXX, andARfor the target platform, but we were only settingCC. This is possibly causing cross-compilation failures for crates that build C++ code via CMake (see heroku/buildpacks-deb-packages#181).Fixes #725