[BUG] Enabling code coverage for arm64-v8a via cmake for native unit test cases throws error __start___llvm_prf_vnds

[arjunkchr]

Description

Enable code coverage flags for cmake for native unit test cases on arm64-v8a via:

set(CMAKE_CODE_COVERAGE_COMPILER_FLAGS "-fprofile-arcs -ftest-coverage -fprofile-instr-generate -fcoverage-mapping")
set(CMAKE_CODE_COVERAGE_LINKER_FLAGS "--coverage")

and then running the native test cases shows the error:

adb -s 89CX089QN shell LD_LIBRARY_PATH=/data/local/tmp/tmp LLVM_PROFILE_FILE=/data/local/tmp/tmp/llvm_profile GCOV_PREFIX=/data/local/tmp/tmp /data/local/tmp/tmp/unittests --gtest_output=xml:/data/local/tmp/tmp/unittests_results.xml
CANNOT LINK EXECUTABLE "/data/local/tmp/tmp/unittests": cannot locate symbol "__start___llvm_prf_vnds" referenced by "/data/local/tmp/tmp/plugin.so"..

The same works fine if the test cases are run with armeabi-v7a so files.

Environment Details

• NDK Version:Tried ndk-r18 and ndk-r20 as well.
• Build system: cmake
• Host OS: MacOS
• ABI: arm64-v8a
• NDK API level: The target SDK being used in gradle is 28.
• Device API level: API 29

[pirama-arumuga-nainar]

This seems like the same underlying issue as #881. I'll investigate both.

[pirama-arumuga-nainar]

This is probably an issue with gradle. The following test works on a Pixel 2, running Q:

$ cat CMakeLists.txt
project(Test)

set(CMAKE_CODE_COVERAGE_COMPILER_FLAGS "-fprofile-arcs -ftest-coverage -fprofile-instr-generate -fcoverage-mapping")
set(CMAKE_CODE_COVERAGE_LINKER_FLAGS "--coverage")

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${CMAKE_CODE_COVERAGE_LINKER_FLAGS}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CMAKE_CODE_COVERAGE_COMPILER_FLAGS}")

add_executable(Test test.cpp)

$ cat test.cpp
int main() {
  return 3;
}

$ cmake .. -G Ninja -DCMAKE_TOOLCHAIN_FILE=$NDK/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a -DANDROID_NATIVE_API_LEVEL=29

If there's a mismatch in what I'm doing, let me know. If not, I'll try to reproduce with Gradle.

[pirama-arumuga-nainar]

Aah, didn't see that the missing symbol was from a shared library. I think CMAKE_CODE_COVERAGE_LINKER_FLAGS is not getting propagated to CMAKE_SHARED_LINKER_FLAGS. (It is probably only passed onto CMAKE_EXE_LINKER_FLAGS).

If I try the same, I get the exact same error about missing symbol. Once I add
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${CMAKE_CODE_COVERAGE_LINKER_FLAGS} "), the error goes away.

But something is still fishy - the armv7 binary works fine even without setting CMAKE_SHARED_LINKER_FLAGS. I'll look at why this is the case.

[DanAlbert]

@pirama-arumuga-nainar did you have a chance to do any more digging here?

[pirama-arumuga-nainar]

Reposting #881 (comment):

I'm apologise for the long delay in investigating this. This seems to be a bug in ld.bfd which may have been fixed in https://sourceware.org/bugzilla/show_bug.cgi?id=24857. To verify, run readelf -aW on the problematic shared library. In my repro, the sh_info for .dynsym is 3 whereas there are at least 11 LOCAL symbols.

If I change the linker to gold or lld, the repro works fine. Please reopen if your particular repro doesn't work with gold or lld.

PS: IIUC lld is going to be the default linker starting r22.