[Overview] Modernization code with clang-tidy

[SunBlack]

This issue is just to have an overview about clang-tidy modernizations.

Full list of clang-tidy checks.

Checks which redirect to another test are removed from following list.

Android:

• android-cloexec-accept (Nothing found)
• android-cloexec-accept4 (Nothing found)
• android-cloexec-creat (Nothing found)
• android-cloexec-dup (Nothing found)
• android-cloexec-epoll-create (Nothing found)
• android-cloexec-epoll-create1 (Nothing found)
• android-cloexec-fopen (discussion: "e" mode string in fopen #2748, PR: Add cloexec option to fopen #2755, Add cloexec option to fopen #3223)
• android-cloexec-inotify-init (Nothing found)
• android-cloexec-inotify-init1 (Nothing found)
• android-cloexec-memfd-create (Nothing found)
• android-cloexec-open (discussion: "e" mode string in fopen #2748, PR: Add cloexec option to fopen #2755)
• android-cloexec-pipe (Nothing found)
• android-cloexec-pipe2 (Nothing found)
• android-cloexec-socket (Nothing found)
• android-comparison-in-temp-failure-retry (Nothing found)

Boost:

• boost-use-to-string (PR: Prefer std::to_string over boost::lexical_cast for integer conversions #2785)

Bugprone:

• bugprone-argument-comment (Nothing found)
• bugprone-assert-side-effect (Nothing found)
• bugprone-bool-pointer-implicit-conversion
• bugprone-branch-clone (Nothing found)
• bugprone-copy-constructor-init
• bugprone-dangling-handle (Nothing found)
• bugprone-exception-escape
• bugprone-fold-init-type (Nothing found)
• bugprone-forward-declaration-namespace
• bugprone-forwarding-reference-overload (Nothing found)
• bugprone-inaccurate-erase (Nothing found)
• bugprone-incorrect-roundings
• bugprone-integer-division
• bugprone-lambda-function-name (Nothing found)
• bugprone-macro-parentheses
• bugprone-macro-repeated-side-effects (Nothing found)
• bugprone-misplaced-operator-in-strlen-in-alloc (Nothing found)
• bugprone-misplaced-widening-cast
• bugprone-move-forwarding-reference (Nothing found)
• bugprone-multiple-statement-macro
• bugprone-narrowing-conversions
• bugprone-parent-virtual-call
• bugprone-posix-return (Nothing found)
• bugprone-sizeof-container (Nothing found)
• bugprone-sizeof-expression
• bugprone-string-constructor (Nothing found)
• bugprone-string-integer-assignment (Nothing found)
• bugprone-string-literal-with-embedded-nul (Nothing found)
• bugprone-suspicious-enum-usage
• bugprone-suspicious-memset-usage (Nothing found)
• bugprone-suspicious-missing-comma (Nothing found)
• bugprone-suspicious-semicolon (Nothing found)
• bugprone-suspicious-string-compare
• bugprone-swapped-arguments (Nothing found)
• bugprone-terminating-continue (Nothing found)
• bugprone-throw-keyword-missing (Nothing found)
• bugprone-too-small-loop-variable (PR: Fix bug prone loop variables that are too small #2829)
• bugprone-undefined-memory-manipulation
• bugprone-undelegated-constructor (Nothing found)
• bugprone-unhandled-self-assignment (Nothing found)
• bugprone-unused-raii (Nothing found)
• bugprone-unused-return-value (Nothing found)
• bugprone-use-after-move (Nothing found)
• bugprone-virtual-near-miss

Cert:

• cert-dcl21-cpp
• cert-dcl50-cpp
• cert-dcl58-cpp (Nothing found)
• cert-env33-c (Nothing found)
• cert-err34-c
• cert-err52-cpp
• cert-err58-cpp
• cert-err60-cpp
• cert-flp30-c
• cert-msc50-cpp
• cert-msc51-cpp
• cert-oop11-cp (Nothing found)

Clang-Analyzer:

• clang-analyzer-apiModeling.StdCLibraryFunctions (Nothing found)
• clang-analyzer-apiModeling.TrustNonnull (Nothing found)
• clang-analyzer-apiModeling.google.GTest (Nothing found)
• clang-analyzer-core.CallAndMessage
• clang-analyzer-core.DivideZero
• clang-analyzer-core.DynamicTypePropagation (Nothing found)
• clang-analyzer-core.NonNullParamChecker
• clang-analyzer-core.NonnilStringConstants (Nothing found)
• clang-analyzer-core.NullDereference
• clang-analyzer-core.StackAddressEscape (Nothing found)
• clang-analyzer-core.UndefinedBinaryOperatorResult (Nothing found)
• clang-analyzer-core.VLASize (Nothing found)
• clang-analyzer-core.builtin.BuiltinFunctions (Nothing found)
• clang-analyzer-core.builtin.NoReturnFunctions (Nothing found)
• clang-analyzer-core.uninitialized.ArraySubscript
• clang-analyzer-core.uninitialized.Assign
• clang-analyzer-core.uninitialized.Branch
• clang-analyzer-core.uninitialized.CapturedBlockVariable (Nothing found)
• clang-analyzer-core.uninitialized.UndefReturn
• clang-analyzer-cplusplus.InnerPointer (Nothing found)
• clang-analyzer-cplusplus.Move (Nothing found)
• clang-analyzer-cplusplus.NewDelete
• clang-analyzer-cplusplus.NewDeleteLeaks
• clang-analyzer-cplusplus.SelfAssignment (Nothing found)
• clang-analyzer-deadcode.DeadStores (PR: Remove dead stores #3095)
• clang-analyzer-llvm.Conventions (check not released in a stable version of clang-tidy)
• clang-analyzer-nullability.NullPassedToNonnull (Nothing found)
• clang-analyzer-nullability.NullReturnedFromNonnull (Nothing found)
• clang-analyzer-nullability.NullableDereferenced (Nothing found)
• clang-analyzer-nullability.NullablePassedToNonnull (Nothing found)
• clang-analyzer-nullability.NullableReturnedFromNonnull (Nothing found)
• clang-analyzer-optin.cplusplus.VirtualCall
• clang-analyzer-optin.mpi.MPI-Checker (Nothing found)
• clang-analyzer-optin.osx.cocoa.localizability.EmptyLocalizationContextChecker (Nothing found)
• clang-analyzer-optin.osx.cocoa.localizability.NonLocalizedStringChecker (Nothing found)
• clang-analyzer-optin.performance.GCDAntipattern (Nothing found)
• clang-analyzer-optin.performance.Padding
• clang-analyzer-optin.portability.UnixAPI (Nothing found)
• clang-analyzer-osx.API (Nothing found)
• clang-analyzer-osx.NumberObjectConversion (Nothing found)
• clang-analyzer-osx.OSObjectRetainCount (Nothing found)
• clang-analyzer-osx.ObjCProperty (Nothing found)
• clang-analyzer-osx.SecKeychainAPI (Nothing found)
• clang-analyzer-osx.cocoa.AtSync (Nothing found)
• clang-analyzer-osx.cocoa.AutoreleaseWrite (Nothing found)
• clang-analyzer-osx.cocoa.ClassRelease (Nothing found)
• clang-analyzer-osx.cocoa.Dealloc (Nothing found)
• clang-analyzer-osx.cocoa.IncompatibleMethodTypes (Nothing found)
• clang-analyzer-osx.cocoa.Loops (Nothing found)
• clang-analyzer-osx.cocoa.MissingSuperCall (Nothing found)
• clang-analyzer-osx.cocoa.NSAutoreleasePool (Nothing found)
• clang-analyzer-osx.cocoa.NSError (Nothing found)
• clang-analyzer-osx.cocoa.NilArg (Nothing found)
• clang-analyzer-osx.cocoa.NonNilReturnValue (Nothing found)
• clang-analyzer-osx.cocoa.ObjCGenerics (Nothing found)
• clang-analyzer-osx.cocoa.RetainCount (Nothing found)
• clang-analyzer-osx.cocoa.RunLoopAutoreleaseLeak (Nothing found)
• clang-analyzer-osx.cocoa.SelfInit (Nothing found)
• clang-analyzer-osx.cocoa.SuperDealloc (Nothing found)
• clang-analyzer-osx.cocoa.UnusedIvars (Nothing found)
• clang-analyzer-osx.cocoa.VariadicMethodTypes (Nothing found)
• clang-analyzer-osx.coreFoundation.CFError (Nothing found)
• clang-analyzer-osx.coreFoundation.CFNumber (Nothing found)
• clang-analyzer-osx.coreFoundation.CFRetainRelease (Nothing found)
• clang-analyzer-osx.coreFoundation.containers.OutOfBounds (Nothing found)
• clang-analyzer-osx.coreFoundation.containers.PointerSizedValues (Nothing found)
• clang-analyzer-security.FloatLoopCounter
• clang-analyzer-security.insecureAPI.UncheckedReturn (Nothing found)
• clang-analyzer-security.insecureAPI.bcmp (Nothing found)
• clang-analyzer-security.insecureAPI.bcopy (Nothing found)
• clang-analyzer-security.insecureAPI.bzero (Nothing found)
• clang-analyzer-security.insecureAPI.getpw (Nothing found)
• clang-analyzer-security.insecureAPI.gets (Nothing found)
• clang-analyzer-security.insecureAPI.mkstemp (Nothing found)
• clang-analyzer-security.insecureAPI.mktemp (Nothing found)
• clang-analyzer-security.insecureAPI.rand (Nothing found)
• clang-analyzer-security.insecureAPI.strcpy
• clang-analyzer-security.insecureAPI.vfork (Nothing found)
• clang-analyzer-unix.API
• clang-analyzer-unix.Malloc
• clang-analyzer-unix.MallocSizeof (Nothing found)
• clang-analyzer-unix.MismatchedDeallocator
• clang-analyzer-unix.StdCLibraryFunctions (check not released in a stable version of clang-tidy)
• clang-analyzer-unix.Vfork (Nothing found)
• clang-analyzer-unix.cstring.BadSizeArg (Nothing found)
• clang-analyzer-unix.cstring.NullArg (Nothing found)
• clang-analyzer-valist.CopyToSelf (Nothing found)
• clang-analyzer-valist.Uninitialized (Nothing found)
• clang-analyzer-valist.Unterminated (Nothing found)

cppcoreguidelines

• cppcoreguidelines-avoid-goto
• cppcoreguidelines-interfaces-global-init (Nothing found)
• cppcoreguidelines-macro-usage
• cppcoreguidelines-narrowing-conversions
• cppcoreguidelines-no-malloc
• cppcoreguidelines-owning-memory
• cppcoreguidelines-pro-bounds-array-to-pointer-decay
• cppcoreguidelines-pro-bounds-constant-array-index
• cppcoreguidelines-pro-bounds-pointer-arithmetic
• cppcoreguidelines-pro-type-const-cast
• cppcoreguidelines-pro-type-cstyle-cast
• cppcoreguidelines-pro-type-member-init
• cppcoreguidelines-pro-type-reinterpret-cast
• cppcoreguidelines-pro-type-static-cast-downcast
• cppcoreguidelines-pro-type-union-access
• cppcoreguidelines-pro-type-vararg
• cppcoreguidelines-slicing
• cppcoreguidelines-special-member-functions

hicpp:

• hicpp-avoid-goto
• hicpp-exception-baseclass
• hicpp-multiway-paths-covered
• hicpp-no-assembler (Nothing found)
• hicpp-signed-bitwise

Misc:

• misc-definitions-in-headers
• misc-misplaced-const
• misc-new-delete-overloads (Nothing found)
• misc-non-copyable-objects (Nothing found)
• misc-non-private-member-variables-in-classes
• misc-redundant-expression
• misc-static-assert (Nothing found)
• misc-throw-by-value-catch-by-reference (Nothing found)
• misc-unconventional-assign-operator
• misc-uniqueptr-reset-release (Nothing found)
• misc-unused-alias-decls (Nothing found)
• misc-unused-parameters
• misc-unused-using-decls

Modernize:

• modernize-avoid-bind (Nothing found)
• modernize-avoid-c-arrays (PR: Use std::array instead of C-array for ColorLUT #4489)
• modernize-concat-nested-namespaces (requires C++17)
• modernize-deprecated-headers (PR: Replace deprecated C library headers #2737)
• modernize-deprecated-ios-base-aliases
• modernize-loop-convert (PR: Tranform classic loops to range-based for loops in module 2d #2835, Transform classic loops to range-based for loops in module search #2836, Transform classic loops to range-based for loops in module tracking #2837, Transform classic loops to range-based for loops in module common #2838, Transform classic loops to range-based for loops in module ml #2839, Transform classic loops to range-based for loops in module geometry #2840, Transform classic loops to range-based for loops in examples #2841, Transform classic loops to range-based for loops in module kdtree #2842, Transform classic loops to range-based for loops in module visualization #2843, Transform classic loops to range-based for loops in module gpu #2844, Transform classic loops to range-based for loops in module gpu #2844, Transform classic loops to range-based for loops in module io #2845, Transform classic loops to range-based for loops in module keypoints #2846, Transform classic loops to range-based for loops in module octree #2847, Transform classic loops to range-based for loops in module outofcore #2848, Transform classic loops to range-based for loops in module people #2849, Transform classic loops to range-based for loops in tools #2850, Transform classic loops to range-based for loops in tests. #2851, Transform classic loops to range-based for loops in module features #2853, Transform classic loops to range-based for loops in module filters #2854, Transform classic loops to range-based for loops in module recognition #2855, Transform classic loops to range-based for loops in module registration #2856, Transform classic loops to range-based for loops in module sample_consensus #2857, Transform classic loops to range-based for loops in module simulation #2858, Transform classic loops to range-based for loops in module segmentation #2859, Transform classic loops to range-based for loops in module surface #2860)
• modernize-make-shared (Nothing found)
• modernize-make-unique (Nothing found)
• modernize-pass-by-value
• modernize-raw-string-literal (PR: Prefer raw strings over escaped strings #2789)
• modernize-redundant-void-arg (PR: Remove unnecessary void parameter #2780)
• modernize-replace-auto-ptr (Nothing found)
• modernize-replace-random-shuffle (PR: Replace random_shuffle by shuffle #3069)
• modernize-return-braced-init-list (PR: Prefer returning braced init list #3039)
• modernize-shrink-to-fit (Nothing found)
• modernize-unary-static-assert (requires C++17)
• modernize-use-auto (developer decision, so no auto transformation, see discussion in Transform classic loops to range-based for loops in module common #2838)
• modernize-use-bool-literals (PR: Prefer using bool literals #2793)
• modernize-use-default-member-init
• modernize-use-emplace (PR: Prefer emplace_back over push_back #2784)
• modernize-use-equals-default (PR: Make empty destructors default or remove them if they seems to be unnecessary #5386)
• modernize-use-equals-delete (PR: Use =delete to disable special members #2779)
• modernize-use-nodiscard (requires C++17)
• modernize-use-noexcept
• modernize-use-nullptr (PR: Use nullptr in module apps #3004, Use nullptr in module common #3005, Use nullptr in module cuda #3006, Use nullptr in module examples #3007, Use nullptr in module features #3008, Use nullptr in module filters #3009, Use nullptr in module geometry #3010, Use nullptr in module gpu #3011, Use nullptr in module io #3012, Use nullptr in module kdtree #3013, Use nullptr in module keypoints #3014, Use nullptr in module ml #3015, Use nullptr in module octree #3016, Use nullptr in module outofcore #3017, Use nullptr in module people #3018, Use nullptr in module recognition #3019, Use nullptr in module registration #3020, Use nullptr in module sample_consensus #3021, Use nullptr in module search #3022, Use nullptr in module segmentation #3023, Use nullptr in module simulation #3024, Use nullptr in module stereo #3025, Use nullptr in module surface #3026, Use nullptr in module test #3027, Use nullptr in module tools #3028, Use nullptr in module visualization #3029)
• modernize-use-override (PR: Modernize code to use override #2728)
• modernize-use-trailing-return-type (check not released in a stable version of clang-tidy)
• modernize-use-transparent-functors (PR: Use transparent functors #3224)
• modernize-use-uncaught-exceptions (requires C++17)
• modernize-use-using (PR: Use using instead of typedef [test] #3112, Use using instead of typedef [2d, ml, search] #3113, Use using instead of typedef [tools, tracking, visualization] #3115, Use using instead of typedef [apps] #3117, Use using instead of typedef [common] #3118, Use using instead of typedef [cuda] #3121, Use using instead of typedef [kdtree, keypoints, octree] #3122, Use using instead of typedef [features] #3123, Use using instead of typedef [registration] #3124, Use using instead of typedef [filters] #3125, Use using instead of typedef [simulation, stereo, surface ] #3129, Use using instead of typedef [segmentation] #3130, Use using instead of typedef [out_of_core, people, recognition, sample_consensus] #3132, Use using instead of typedef [gpu] #3134, Use using instead of typedef [geometry] #3137, Use using instead of typedef [io] #3138, Use using instead of typedef #3139)

MPI

• mpi-buffer-deref (Nothing found)
• mpi-type-mismatch (Nothing found)

OpenMP

• openmp-exception-escape (Nothing found)
• openmp-use-default-none (PR: Use default(none) for OpenMP definitions #3524)

Performance

• performance-faster-string-find (PR: Improve performance of finding single character in strings #2794)
• performance-for-range-copy (Nothing found)
• performance-implicit-conversion-in-loop (requires Adjust code to match current FLANN API #3234)
• performance-inefficient-algorithm (Nothing found)
• performance-inefficient-string-concatenation (discussion: [Clang-Tidy] Inefficient string concatenation #3233)
• performance-inefficient-vector-operation (Nothing found)
• performance-move-const-arg (Nothing found)
• performance-move-constructor-init (Nothing found)
• performance-noexcept-move-constructor (Nothing found)
• performance-type-promotion-in-math-fn (PR: Force C++ over C math function #3087)
• performance-unnecessary-copy-initialization
• performance-unnecessary-value-param (PR: Add missing std::move or const reference for parameters #3232, Add missing std::move or const reference for parameters #3253)

Readability:

• readability-avoid-const-params-in-decls
• readability-braces-around-statements
• readability-const-return-type
• readability-container-size-empty (PR: Prefer empty() over size() when checking container state #3033)
• readability-delete-null-pointer (PR: Remove unnecessary nullptr checks before delete #2990)
• readability-deleted-default (Nothing found)
• readability-else-after-return (PR: Remove else after return statement [2d, apps, common, cuda, examples, features, filters, geometry, gpu] #3180, Remove else after return statement [io] #3181, Remove else after return statement [kdtree, keypoints, ml, octree] #3182, Remove else after return statement [outofcore] #3183, Remove else after return statement [people, recognition, registration] #3184, Remove else after return statement [sample_consensus, search, segmentation, stereo, surface] #3185, Remove else after return statement [test, tools, tracking, visualization] #3186)
• readability-function-size
• readability-identifier-naming (Nothing found)
• readability-implicit-bool-conversion
• readability-inconsistent-declaration-parameter-name
• readability-isolate-declaration
• readability-magic-numbers
• readability-make-member-function-const (PR: Mark non-const and non-modifying member functions as const #3836)
• readability-misleading-indentation
• readability-misplaced-array-index (Nothing found)
• readability-named-parameter
• readability-non-const-parameter
• readability-redundant-control-flow
• readability-redundant-declaration (Nothing found)
• readability-redundant-function-ptr-dereference (Nothing found)
• readability-redundant-member-init (PR: Remove redundant member field initialization #3070)
• readability-redundant-preprocessor (Nothing found)
• readability-redundant-smartptr-get (Nothing found)
• readability-redundant-string-cstr (PR: Remove redundant calls to std::string::c_str() #3517)
• readability-redundant-string-init (PR: Remove redundant string initialization with "" #2758)
• readability-simplify-boolean-expr (PR: Simplify boolean expressions #2790)
• readability-simplify-subscript-expr
• readability-static-accessed-through-instance (PR: Fix access to static members through instances #2776)
• readability-static-definition-in-anonymous-namespace (Nothing found)
• readability-string-compare (PR: Improve readability of string comparisons #2986)
• readability-uniqueptr-delete-release (Nothing found)
• readability-uppercase-literal-suffix

Not relevant checks:

• abseil-*
• fuchsia-*
• google-*
• llvm-*
• objc-*
• portability-simd-intrinsics (experimental part of std)
• zircon-*

In case you see a modernization we could apply or can't apply, feel free to write it as comment. In case there is a modernization that needs discussion, open a new issue and write reference to it as comment, so I can add it to this list.

[jasjuang]

I think modernize-use-auto makes a lot of sense for iterators, but for new expressions and cast expressions to make sense, MinTypeNameLength has to be at least larger or equal the default 5.

modernize-avoid-c-arrays and modernize-deprecated-headers is definitely needed.

I think modernize-make-shared, modernize-make-unique, modernize-use-emplace, modernize-use-nullptr are also good to add in.

[taketwo]

modernize-use-auto: be very careful with Eigen types. Basically, do not use the auto keywords with Eigen's expressions, unless you are 100% sure about what you are doing (ref).

[SunBlack]

@jasjuang modernize-make-shared & modernize-make-unique will not have any effect, because we didn't had C++11 before ;).

[SunBlack]

I added two points for discussion.

[SunBlack]

I think modernize-use-auto makes a lot of sense for iterators, but for new expressions and cast expressions to make sense, MinTypeNameLength has to be at least larger or equal the default 5.

@jasjuang Discussion is for this is currently here: #2838 - in case you want to be part of it ;)

[denix56]

Maybe we should also replace typedef with using ? Clang also suggests it as modernization. Moreover, it is, imho, much more readable

[taketwo]

It'd certainly be nice to switch to using in the long run. @SunBlack already attempted to apply automatic fix, but there were problems, see #2791.

[SunBlack]

I suggest to skip modernize-use-default-member-init, because I really don't like to have default values stored in header.

[taketwo]

Generally, I agree with you on this. However, due to the fact that PCL is a heavily templated library, we already have default values in ".h" files most of the times. And even if we don't have them in ".h", then they are in ".hpp", which is effectively the same. Meantime, there are benefits in using default member init. For example, when there are multiple constructors (which is often the case in PCL) it helps to maintain consistency between default values.

[SergioRAgostinho]

Just wanted to add here the decision we took for readability-implicit-bool-conversion. tldr activate the option AllowPointerConditions at that time. See this comment for reference

[SunBlack]

Just to mention: I don't believe we can integrate clang-tidy in near feature into build server. I tried it in our project, but there are some issues:

• I have no idea how header-filter really works. It should be a Regex, but I don't know which syntax they allow, because all my regexe works just partially (need to exclude moc and ui files of Qt from output)
• If we switch to AUTOMOC, AUTOUI and AUTORCC, these file will not anymore generated during CMake generation phase. Instead they will be generated at start of a build (there are _autogen targets then). So we need to build all _autogen targets to get run clang-tidy (if not clang-tidy will complain missing moc/ui/rcc files). Because there is no global autogen target, we need to write a script to grep all _autogen targets of makefile, because makefiles doesn't support wildcard, so we can't call make *_autogen. Easiest solution use CMake 3.14 and CMAKE_EXPORT_COMPILE_COMMANDS=ON
• Output of clang-tidy 6.0 / 7 / 8 produces sometimes corrupted output, if you parse console output (starts printing output a hit within another hit). So in case we want to parse output, we need to use a YAML parser (this output seems to be valid)
• Not sure how long a run will need on Azure, could be longer than MSVC build ;).

[taketwo]

Not sure how long a run will need on Azure, could be longer than MSVC build ;).

😱 In case it turns out to be very expensive to run, we may consider making it a periodic job which runs, say, weekly.

But the rest of the items you posted make this all sound like a very daunting task.

[SunBlack]

General question, due to:

Lack of time to review. Like I said, I'm not putting any priority in reviewing these PRs because they are time consuming and not in the goals for this release. That being said, they are fairly trivial in the changes they make, so feel I'm perfectly ok in merging them with just your review.

Originally posted by @SergioRAgostinho in #3112 (comment)

Should I stop applying modernization until release of 1.10.0 or still continue?

[SergioRAgostinho]

If you have time to spare, I would rather have your help on the transition to std until the release is complete. There are a couple of items now that are simply manual labor, e.g.: the bind -> lambda replacement. But let Sergey express his opinion, since he was still reviewing things.