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

Mehmet Erol Sanliturk via cfe-dev cfe-dev at lists.llvm.org
Wed Sep 5 08:39:49 PDT 2018 

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
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