How to build asan with clang?

[spacewander]

Title: I need some help for building asan with clang

Description:
I tried bazel test --config=clang-asan ..., but got:

ld.lld: error: undefined symbol: __muloti4
>>> referenced by numbers.cc
>>>               bazel-out/k8-fastbuild/bin/external/com_google_absl/absl/strings/_objs/strings/numbers.pic.o:(absl::operator*(absl::int128, absl::int128))
clang: error: linker command failed with exit code 1

After applying the solution in https://bugs.llvm.org/show_bug.cgi?id=16404

diff --git .bazelrc .bazelrc
index 6a7cd55d0..7d9c1ef49 100644
--- .bazelrc
+++ .bazelrc
@@ -69,6 +69,7 @@ build:asan --copt -fno-optimize-sibling-calls
 # Clang ASAN/UBSAN
 build:clang-asan --config=asan
 build:clang-asan --linkopt -fuse-ld=lld
+build:clang-asan --linkopt -rtlib=compiler-rt

 # macOS ASAN/UBSAN
 build:macos --cxxopt=-std=c++1

now I get:

ld.lld: error: undefined symbol: _Unwind_Backtrace
>>> referenced by sanitizer_unwind_linux_libcdep.cpp.o:(__sanitizer::BufferedStackTrace::UnwindSlow(unsigned long, unsigned int)) in archive /usr/lib/llvm-11/lib/clang/11.0.1/lib/linux/libclang_rt.asan-x86_64.a
>>> referenced by sanitizer_unwind_linux_libcdep.cpp.o:(__sanitizer::BufferedStackTrace::UnwindSlow(unsigned long, void*, unsigned int)) in archive /usr/lib/llvm-11/lib/clang/11.0.1/lib/linux/libclang_rt.asan-x86_64.a

ld.lld: error: undefined symbol: _Unwind_GetIP
>>> referenced by sanitizer_unwind_linux_libcdep.cpp.o:(__sanitizer::(anonymous namespace)::Unwind_Trace(_Unwind_Context*, void*)) in archive /usr/lib/llvm-11/lib/clang/11.0.1/lib/linux/libclang_rt.asan-x86_64.a
clang: error: linker command failed with exit code 1

Maybe I miss something? I am using Ubuntu 20.04 & clang 11. It would be great if anyone provides me some help.

[caitong93]

Plz try ./ci/run_envoy_docker.sh 'bazel test --config=clang-asan ..' . It's suggested to use docker build to keep ur local development environment same as others https://github.com/envoyproxy/envoy/tree/master/ci#on-linux .

[spacewander]

It seems the docker used by ./ci/run_envoy_docker.sh doesn't contain clang.

./ci/run_envoy_docker.sh 'echo $(which clang)'

./ci/run_envoy_docker.sh 'echo $(which gcc)'
/usr/bin/gcc

[caitong93]

See https://github.com/envoyproxy/envoy/blob/master/ci/build_setup.sh#L84

[nareddyt]

So it seems like some of the bazel flags from

envoy/bazel/setup_clang.sh

Line 26 in e90d674

build:clang-asan --action_env=ENVOY_UBSAN_VPTR=1

are needed. These are not set for clang-asan in the root-level bazelrc by default, only added for CI. Wonder why.

[nareddyt]

The issue seems related to #13973. Unfortunately I had no luck setting those extra bazel flags, so I had to disable Ubsan for now. GoogleCloudPlatform/esp-v2#462 and envoyproxy/nighthawk#593 track this.

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