[question] Cross compiling with Clang

[johningve]

What is your question?

Hi! I want to cross compile for an armv8 Linux host using clang on Linux.

I have tried to follow the documentation, but I'm having the problem that several recipes are built for x86_64 instead. I suspect this is because my clang compiler supports both x86_64 (the default) and armv8, and the target needs to be specified using the --target flag. However, if I add this flag to my build profile via CXXFLAGS it breaks other recipes that need to build native tools.

I noticed that the documentation seems to be assuming "gcc-style" cross compilation where you have a separate compiler named aarch64-linux-gnu-gcc or something. Does conan actually support this "clang-style" cross compiling?

I have set up the profile like this:

File (linux-base)

C_COMPILER_NAME=clang
CXX_COMPILER_NAME=clang++
COMPILER_VERSION=16
[settings]
os=Linux
compiler=$C_COMPILER_NAME
compiler.version=$COMPILER_VERSION
compiler.libcxx=libstdc++11
[options]
[build_requires]
[env]
CC=$C_COMPILER_NAME-$COMPILER_VERSION
CXX=$CXX_COMPILER_NAME-$COMPILER_VERSION

[conf]
tools.build:jobs=18

File (linux-base-armv8)

include(./linux-base)

target_host=aarch64-linux-gnu
toolchain=/usr/aarch64-linux-gnu

[settings]
arch=armv8

[env]
CONAN_CMAKE_FIND_ROOT_PATH=$toolchain  # Optional, for CMake to find things in that folder
CONAN_CMAKE_SYSROOT=$toolchain  # Optional, if we want to define sysroot

I am using conan 1.61 for now, but may consider updating to 2.0 if that supports my use case.

Have you read the CONTRIBUTING guide?

• [X] I've read the CONTRIBUTING guide

[jwillikers]

This should be possible. I'd recommend using the conf variables instead though to set the cross compiler, CMake toolchain, and compiler / linker flags as needed. See here.

[y9luiz]

Hi, any update on this? I've a similar issue, I'm trying to cross compiling a project from a mac system to a raspberry. The project uses conan as package manager and I would like to build it using clang

[franramirez688]

Hi @johningve @y9luiz

Sorry for the long delay 😞

Cross-compiling with Clang should not be an issue at all, but it could be challenging if you are still using the legacy toolchains and build-helpers. We recommend migrating to the modern tools (see more info here), and, if possible, to Conan v2 for sure.

For instance:

host_profile

[settings]
arch=armv8
os=Linux
compiler=clang
compiler.version=16
compiler.libcxx=libstdc++11

[buildenv]
# extra env flags: AR, AS, LD, ...

[conf]
tools.build:cxxflags=["--flag1", "--flag2"]
tools.build:cflags=["--flag3", "--flag4"]
tools.build:compiler_executables={"c": "clang-16", "cpp": "clang++-16"}
tools.build:sysroot=/usr/aarch64-linux-gnu

I also recommend reading the cross-building section with Conan v2.