termux/termux-packages

libllvm does not create a native llvm-config

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#879 opened on Mar 25, 2017

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Description

Cross compiling llvm builds a native (host=build) version of llvm-config as a make step. But in termux, this is not the case. The native llvm-config is built for target host. The native build takes place in $TERMUX_PKG_BUILDDIR/NATIVE. I was unable to find the root cause, but, the native build also uses $TERMUX_STANDALONE_TOOLCHAIN/bin/clang++. I suspect that this may be a bug in the cross compilation mechanism of cmake itself.

This is required to build rustc and other packages dependent on llvm-config.

Contributor guide

Tech stack
cppshell
Domain
build systemdevops
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
needs investigation
Prerequisites
Understanding of Termux package build systemKnowledge of CMake cross compilationFamiliarity with LLVM build scriptsExperience with native vs cross builds
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Investigate why the native build of llvm config uses the cross toolchain instead of host. Check CMake variables like CMAKE CROSSCOMPILING and how the native build is invoked in the LLVM CMakeLists.txt. Look at termux packages/packages/libllvm/build.sh for cmake arguments. Search for comments or recent changes in the issue thread.