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Type:
Improvement
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Resolution: Done
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Priority:
Major - P3
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None
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Affects Version/s: None
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Component/s: None
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None
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Build
When adding -fsanitize=undefined to a bazel target's copt, it invokes clang with a series of options instead of -fsanitize=undefined:
/home/ubuntu/mongo/build/bazelisk build --//bazel/config:compiler_type=clang --//bazel/config:build_mode=opt_debug --//bazel/config:separate_debug=False --//bazel/config:libunwind=auto --//bazel/config:use_gdbserver=False --//bazel/config:spider_monkey_dbg=False --//bazel/config:allocator=system --//bazel/config:use_lldbserver=False --//bazel/config:use_wait_for_debugger=False --//bazel/config:use_ocsp_stapling=True --//bazel/config:use_disable_ref_track=False --//bazel/config:use_wiredtiger=True --//bazel/config:use_glibcxx_debug=False --//bazel/config:build_grpc=False --//bazel/config:use_libcxx=False --//bazel/config:detect_odr_violations=False --//bazel/config:linkstatic=True --//bazel/config:use_diagnostic_latches=False --//bazel/config:shared_archive=False --//bazel/config:linker=lld --//bazel/config:streams_release_build=True --//bazel/config:build_enterprise=False --//bazel/config:visibility_support=auto --platforms=//bazel/platforms:linux_arm64_clang --host_platform=//bazel/platforms:linux_arm64_clang --compilation_mode=dbg --//bazel/config:http_client=True --//bazel/config:ubsan=True --//bazel/config:asan=False //src/mongo/platform:visibility_test1 --config=local -fsanitize=alignment,array-bounds,bool,builtin,enum,float-cast-overflow,integer-divide-by-zero,nonnull-attribute,null,pointer-overflow,return,returns-nonnull-attribute,shift-base,shift-exponent,signed-integer-overflow,unreachable,vla-bound,vptr
It's possible there's logic in bazel's internals to perform this switch, but it's unclear why it's doing it and if it is actually equivalent to -fsanitize=undefined.
A symptom of this issue appears to be that -fno-sanitize on specific suboptions of ubsan is also ignored. We can work around this issue by manually expanding -fsanitize=undefined ourselves, but it's messy.
The list of sanitizers bazel is passing in is functionally identical to -fsanitize=undefined:
https://github.com/llvm-mirror/clang/blob/master/include/clang/Basic/Sanitizers.def#L134 so we won't lose/gain any coverage unintentionally.