[cfe-dev] Random non-reproducible errors in ClangdTests

Mehmet Erol Sanliturk via cfe-dev cfe-dev at lists.llvm.org
Wed Sep 5 20:26:38 PDT 2018 

On Wed, Sep 5, 2018 at 11:55 PM, Kirill Bobyrev via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hi Mikael,
>
> Thanks for pointing that out! Could you share information about what
> compiler + system you used to build and run tests? Sometimes, UB is
> relatively easy to reproduce using the same setup.
>
> As Mehmet mentioned, it looks that there might be uninitialised variable
> given the Valgrind log that you provided.
>
> Could you please attach the whole log so that it would be easier for us to
> understand the cause of problem(s)?
>
> +clangd-dev
>
> Kind regards,
> Kirill
>
>







The following reasons may also be considered :


A memory chip or memory management chip or a line in the main board if
failing slowly .


If some values are read from disk and used , disk surface failures or cable
connection point oxidization may also cause arbitrary data corruptions .



Mehmet Erol Sanliturk














> On 5 Sep 2018, at 17:39, Mehmet Erol Sanliturk via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>
>
> On Wed, Sep 5, 2018 at 4:19 PM, Mikael Holmén via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> Hi,
>>
>> For a while now we randomly see failures when running the ClangdTests
>> test.
>>
>> E.g the below but sometimes other failures:
>>
>> --------
>> FAIL: Extra Tools Unit Tests :: clangd/./ClangdTests/WorkspaceSymbolsTest.Namespaces
>> (16172 of 39758)
>> ******************** TEST 'Extra Tools Unit Tests ::
>> clangd/./ClangdTests/WorkspaceSymbolsTest.Namespaces' FAILED
>> ********************
>> Note: Google Test filter = WorkspaceSymbolsTest.Namespaces
>> [==========] Running 1 test from 1 test case.
>> [----------] Global test environment set-up.
>> [----------] 1 test from WorkspaceSymbolsTest
>> [ RUN      ] WorkspaceSymbolsTest.Namespaces
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:151:
>> Failure
>> Value of: getSymbols("a")
>> Expected: has 4 elements and there exists some permutation of elements
>> such that:
>>  - element #0 (named "ans1") and (in container ""), and
>>  - element #1 (named "ai1") and (in container "ans1"), and
>>  - element #2 (named "ans2") and (in container "ans1"), and
>>  - element #3 (named "ai2") and (in container "ans1::ans2")
>>   Actual: {}
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:153:
>> Failure
>> Value of: getSymbols("::")
>> Expected: has 1 element that (named "ans1") and (in container "")
>>   Actual: {}
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:155:
>> Failure
>> Value of: getSymbols("::a")
>> Expected: has 1 element that (named "ans1") and (in container "")
>>   Actual: {}
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:158:
>> Failure
>> Value of: getSymbols("ans1::")
>> Expected: has 2 elements and there exists some permutation of elements
>> such that:
>>  - element #0 (named "ai1") and (in container "ans1"), and
>>  - element #1 (named "ans2") and (in container "ans1")
>>   Actual: {}
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:160:
>> Failure
>> Value of: getSymbols("::ans1")
>> Expected: has 1 element that (named "ans1") and (in container "")
>>   Actual: {}
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:163:
>> Failure
>> Value of: getSymbols("::ans1::")
>> Expected: has 2 elements and there exists some permutation of elements
>> such that:
>>  - element #0 (named "ai1") and (in container "ans1"), and
>>  - element #1 (named "ans2") and (in container "ans1")
>>   Actual: {}
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:165:
>> Failure
>> Value of: getSymbols("::ans1::ans2")
>> Expected: has 1 element that (named "ans2") and (in container "ans1")
>>   Actual: {}
>> ../tools/clang/tools/extra/unittests/clangd/FindSymbolsTests.cpp:167:
>> Failure
>> Value of: getSymbols("::ans1::ans2::")
>> Expected: has 1 element that (named "ai2") and (in container "ans1::ans2")
>>   Actual: {}
>> [  FAILED  ] WorkspaceSymbolsTest.Namespaces (39 ms)
>> [----------] 1 test from WorkspaceSymbolsTest (39 ms total)
>>
>> [----------] Global test environment tear-down
>> [==========] 1 test from 1 test case ran. (40 ms total)
>> [  PASSED  ] 0 tests.
>> [  FAILED  ] 1 test, listed below:
>> [  FAILED  ] WorkspaceSymbolsTest.Namespaces
>>
>>  1 FAILED TEST
>>
>>
>> It can fail and then at once pass again so something funny is going on.
>>
>>
>> I ran valgrind on ClangdTests and then I got a bunch of complaints, the
>> first being:
>>
>>
>> [ RUN      ] ClangdVFSTest.SearchLibDir
>> Updating file /clangd-test/foo.cpp with command [/clangd-test] clang
>> -ffreestanding -xc++ -target x86_64-linux-unknown -m64
>> --gcc-toolchain=/randomusr -stdlib=libstdc++ /clangd-test/foo.cpp
>> -resource-dir=/data/repo/llvm-patch/build-all/tools/clang/to
>> ols/extra/unittests/clangd/../lib/clang/8.0.0
>> Preamble for file /clangd-test/foo.cpp cannot be reused. Attempting to
>> rebuild it.
>> Built preamble of size 175020 for file /clangd-test/foo.cpp
>> ==14605== Thread 2 worker:foo.cpp:
>> ==14605== Conditional jump or move depends on uninitialised value(s)
>> ==14605==    at 0xCDF8A6: clang::Sema::SetCtorInitializers(clang::CXXConstructorDecl*,
>> bool, llvm::ArrayRef<clang::CXXCtorInitializer*>) (in
>> /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0xD01CB9: clang::Sema::DefineImplicitDef
>> aultConstructor(clang::SourceLocation, clang::CXXConstructorDecl*) (in
>> /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0xEA3B93: PerformConstructorInitialization(clang::Sema&,
>> clang::InitializedEntity const&, clang::InitializationKind const&,
>> llvm::MutableArrayRef<clang::Expr*>, clang::InitializationSequence::Step
>> const&, bool&, bool, bool, clang::SourceLocation, clang::SourceLocation)
>> (in /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0xE9AA3F: clang::InitializationSequence::Perform(clang::Sema&,
>> clang::InitializedEntity const&, clang::InitializationKind const&,
>> llvm::MutableArrayRef<clang::Expr*>, clang::QualType*) (in
>> /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0xBFA3C4: clang::Sema::ActOnUninitializedDecl(clang::Decl*)
>> (in /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0x13C5EFF: clang::Parser::ParseDeclaratio
>> nAfterDeclaratorAndAttributes(clang::Declarator&,
>> clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*)
>> (in /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0x13C40B7: clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&,
>> clang::DeclaratorContext, clang::SourceLocation*,
>> clang::Parser::ForRangeInit*) (in /data/repo/llvm-patch/build-al
>> l/tools/clang/tools/extra/unittests/clangd/ClangdTests)
>> ==14605==    by 0x13AAF5B: clang::Parser::ParseDeclOrFunc
>> tionDefInternal(clang::Parser::ParsedAttributesWithRange&,
>> clang::ParsingDeclSpec&, clang::AccessSpecifier) (in
>> /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0x13AAA1D: clang::Parser::ParseDeclaratio
>> nOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&,
>> clang::ParsingDeclSpec*, clang::AccessSpecifier) (in
>> /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0x13A9861: clang::Parser::ParseExternalDe
>> claration(clang::Parser::ParsedAttributesWithRange&,
>> clang::ParsingDeclSpec*) (in /data/repo/llvm-patch/build-al
>> l/tools/clang/tools/extra/unittests/clangd/ClangdTests)
>> ==14605==    by 0x13A8629: clang::Parser::ParseTopLevelDe
>> cl(clang::OpaquePtr<clang::DeclGroupRef>&) (in
>> /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==    by 0x13A840F: clang::Parser::ParseFirstTopLe
>> velDecl(clang::OpaquePtr<clang::DeclGroupRef>&) (in
>> /data/repo/llvm-patch/build-all/tools/clang/tools/extra/unit
>> tests/clangd/ClangdTests)
>> ==14605==
>> Updating file /clangd-test/foo.cpp with command [/clangd-test] clang
>> -ffreestanding -xc++ -target x86_64-linux-unknown -m64
>> --gcc-toolchain=/randomusr -stdlib=libstdc++ /clangd-test/foo.cpp
>> -resource-dir=/data/repo/llvm-patch/build-all/tools/clang/to
>> ols/extra/unittests/clangd/../lib/clang/8.0.0
>> Reusing preamble for file /clangd-test/foo.cpp
>> [       OK ] ClangdVFSTest.SearchLibDir (952 ms)
>>
>>
>>
>> It's not obvious to me what the problem really is. Does anyone here have
>> a clue?
>>
>> Regards,
>> Mikael
>> _______________________________________________
>
>
>
>
>
> One reason of non-reproducible errors in a program is mainly
> "uninitialized variables" .
> These variables uses whatever remains in the memory from previous
> allocations and used by the new program .
> Therefore when these values are used , program behavior is unexpected .
>
>
> Another may be "array index showing outside of an array" . Especially in
> loops , if loop passes array boundaries toward up or down  .
> Or , when a value is directly used to index an array , but it is out of
> bounds .
>
>
> The above reasons are not , "all" , but "some" .
>
>
>
>
> Mehmet Erol Sanliturk
>
>
>
>
>
>
> _______________________________________________
> cfe-dev mailing list
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>
>
>
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