From: Peter Marko <[email protected]>
This assignment was present in scarthgap meta-clang.
* commit adding it: [1]
* commit removing it from native case: [2]
* it was removed completely when migrating clang to oe-core
After migration from scarthgap to wrynose (or current master), clang
extra tools like clang-tidy do not work anymore.
Test recipe used for fix validation:
test-recipe.bb:
SUMMARY = "clang-tidy demonstration program"
SECTION = "examples"
HOMEPAGE = "n/a"
LICENSE = "GPL-2.0-only"
LIC_FILES_CHKSUM =
"file://${COREBASE}/meta/files/common-licenses/GPL-2.0-only;md5=801f80980d171dd6425610833a22dbe6"
SRC_URI = "file://CMakeLists.txt file://hello-world.cpp"
S = "${UNPACKDIR}"
TOOLCHAIN = "clang"
inherit cmake
CMakeLists.txt
project(hello-world)
cmake_minimum_required(VERSION 3.5)
find_program(CLANG_TIDY NAMES clang-tidy)
set(CMAKE_CXX_CLANG_TIDY "${CLANG_TIDY}" "--checks=*")
add_executable(${PROJECT_NAME} hello-world.cpp)
hello-world.cpp
#include <iostream>
int main() {
std::cout << "Hello World!";
return 0;
}
I have asked AI agent to analyze clang sources for side-effects which
are mentioned in patch removing this with following result:
When a cmake recipe uses CMAKE_CXX_CLANG_TIDY (or runs clang-tidy in any
mode that passes the compile command via -- on the command line), CMake
invokes clang-tidy through its __run_co_compile path. This path
constructs a FixedCompilationDatabase from the arguments following --.
Inside FixedCompilationDatabase::loadFromCommandLine() the original
cross-compiler binary name (e.g. x86_64-poky-linux-clang++) is stripped
by stripPositionalArgs() and replaced with a dummy argv[0]. As a result
the target triple encoded in the cross-compiler name is never seen by
clang-tidy.
JSONCompilationDatabase (used when clang-tidy is run with -p <build_dir>)
wraps its commands with inferTargetAndDriverMode(), which calls
addTargetAndModeForProgramName() and would correctly inject
--target=x86_64-poky-linux. FixedCompilationDatabase has no equivalent
step, so the native clang-tidy falls back to the build-host default
triple and cannot locate C++ headers under the target sysroot:
hello-world.cpp:1:10: error: 'iostream' file not found
The fix is to make the -target flag explicit in the compile commands.
The cross-compiler already has LLVM_DEFAULT_TARGET_TRIPLE compiled in as
HOST_SYS, so adding -target ${HOST_SYS} to HOST_CC_ARCH is a no-op for
the compiler itself. For clang-tidy and other Clang-based tools that
parse compile commands but do not inherit the binary's baked-in default
triple the flag is the only reliable channel to communicate the intended
target.
On a typical GNU/Linux host the GCC runtime is installed under a
vendor-qualified tuple (e.g. aarch64-linux-gnu/) that clang probes at
runtime. Providing an explicit -target aarch64-linux overrides that
probe and prevents clang-native from finding libgcc and crt objects,
which was the original motivation for removing the assignment.
[1]
https://github.com/kraj/meta-clang/commit/503aa977b27be0506fb6ac21fbf9e8b049b82247
[2]
https://github.com/kraj/meta-clang/commit/6da0abaa33b458a37b97f42e3755245e3220bf27
Signed-off-by: Peter Marko <[email protected]>
---
meta/classes/toolchain/clang.bbclass | 3 +++
1 file changed, 3 insertions(+)
diff --git a/meta/classes/toolchain/clang.bbclass
b/meta/classes/toolchain/clang.bbclass
index 9a3cd0e584..862ecb5e10 100644
--- a/meta/classes/toolchain/clang.bbclass
+++ b/meta/classes/toolchain/clang.bbclass
@@ -34,6 +34,9 @@ LDFLAGS:append:class-nativesdk:x86-64 = "
-Wl,-dynamic-linker,${base_libdir}/ld-
LDFLAGS:append:class-nativesdk:aarch64 = "
-Wl,-dynamic-linker,${base_libdir}/ld-linux-aarch64.so.1"
LDFLAGS:append:class-cross-canadian = "
-Wl,-dynamic-linker,${base_libdir}/placeholder/to/be/rewritten/by/sdk/installer"
+# helps extra tools like clang-tidy to find arch-specific macros and headers
in a cross compile environment
+HOST_CC_ARCH:prepend = "-target ${HOST_SYS} "
+
# do_populate_sysroot needs STRIP, do_package_qa needs OBJDUMP
POPULATESYSROOTDEPS:append:class-target = " llvm-native:do_populate_sysroot"
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