.clang-tidy

---
# Classes of checks we enable, exclusions are listed further down:
# * All clang diagnostic and analyzer checks are enabled.
# * All CERT checks are enabled, many are disabled as the rules to cause a lot
#   of collateral fallout.  CERT does not make their justifications
#   publicly available, so it is hard to understand their rationale.
# * All High Integrity C++ checks are enabled, though again many are excluded.
# * Various other bug-pattern checks: Bugprone, High-Integrity C++,
#   Miscellaneous.  All with exclusions where they seem to cause harm.
# * Readability and modernization checks, though with exclusions that
#   sometimes just relate to style so far.
# * Concurrency orientated checks.
# * Performance orientated checks.
#
# Classes of checks that we do not enable:
# * We ignore all codebase specific checks (Google, Android, etc), except for
#   LLVM checks and Google Test checks.  We disable the checks that are related
#   purely to coding style though, as we don't follow LLVM style.
# * We do not enable the cppcoreguidelines checks because a quick attempt
#   suggests that they are not appropriate for our codebase.  A deeper analysis
#   could result in some specific checks being enabled after fixes.
#
# Use `clang-tidy --list-checks` inside the codebase, so that this file is
# parsed, to see what checks run.
#
# Individual tests that are concretely undesirable in ComputeAorta:
#   * bugprone-reserved-identifier, cert-dcl37-c, cert-dcl51-cpp - These all
#     hit on using `__foo` names as that is a reserved pattern.  But it's
#     reserved for the compiler, and ComputeAorta is a compiler.
#   * bugprone-signed-char-misuse - Triggers on valid code around `int8_t`
#     being implicitly converted to `int`.  Wants to go via `unsigned char`
#     which is just concretely wrong for us.
#   * cert-dcl21-cpp - Makes copies of iterators const for no benefit.
#   * clang-analyzer-cplusplus.NewDeleteLeaks - Seems to result in many false
#     positives in compiler code that uses FooInst::Create.
#   * clang-analyzer-optin.performance.Padding - Would result in lots of noise
#     if rearranging tables, creating diffs harder to review.
#   * hicpp-named-parameter, readability-named-parameter - Insists on
#     parameter names being present as a comment, which just adds noise.
#   * misc-misplaced-const - Incompatible with using OpenCL types in our code,
#     it wants to put const in the middle of OpenCL types, `cl_context` etc,
#     but we can't modify those.
#   * misc-unused-parameters - Already use an equivalent compiler warning,
#     that we explicitly disable per-file where desirable.  Hard to disable
#     clang-tidy checks per-file, so just leave it off.
#   * readability-function-cognitive-complexity - This is tunable, so could set
#     this to a large number, but essentially this problem is too endemic to
#     fix. Also, OpenCL and Vulkan APIs naturally result in complex entry
#     points.
#   * readability-magic-numbers - This just hits far far too often for us.
#   * misc-no-recursion - ComputeAorta chooses to use recursion.
#   * readability-redundant-member-init - Makes code less readable, because you
#     end up with partial member initialization lists when some members are
#     default constructed and some are not.
#
# Individual tests that are maybe undesirable in ComputeAorta, perhaps enable
# and use specific `NOLINT(check-name-here)` exclusions:
#   * bugprone-branch-clone - Many of the clones improve readability.
#   * bugprone-macro-parentheses - Applying the suggested fixes often results
#     in code that does not compile, especially when types are passed as macro
#     parameters.
#   * bugprone-not-null-terminated-result - Dubious memcpy conversions.
#   * bugprone-use-after-move - UnitCargo does weird stuff on purpose.
#   * bugprone-sizeof-expression - These checks make sense, but the CL, Core,
#     and VK interfaces all use lots of opaque types, which means lots of
#     `sizeof(A*)` type code which this check warns on.  I hope in the future
#     that there is a configuration option for this particular sub-class of
#     this check.
#   * cert-dcl59-cpp - Following this makes things verbose?
#   * concurrency-mt-unsafe - The warnings are fundamentally true, but it
#     complains about uses of things such as `std::getenv` when there is no
#     real alternative.
#   * google-readability-avoid-underscore-in-googletest-name - The Google Test
#     FAQ gives good reasons for this, but we have many test names with `_`.
#   * misc-macro-parentheses - See bugprone-macro-parentheses.
#   * misc-redundant-expression - Complains about things like
#     `static_assert(MACRO1 == MACRO2, "");` where the expression is always
#     true, but `[static_]assert` is meant to be always true.
#   * performance-no-int-to-ptr - The logic behind this is good, but it hits on
#     casting error codes to pointers, which is sometimes functionally
#     required.
#
# Still to be considered (i.e. either fixed, left for later, or document why
# they are disabled):
#   * bugprone-forwarding-reference-overload  # Wait for C++14 enable_if_t?
#   * bugprone-narrowing-conversions
#   * bugprone-parent-virtual-call
#   * bugprone-too-small-loop-variable
#   * cert-err34-c
#   * cert-err58-cpp
#   * cert-flp30-c
#   * cert-msc30-c
#   * cert-msc32-c
#   * cert-msc50-cpp
#   * cert-msc51-cpp
#   * cert-oop11-cpp
#   * cert-oop54-cpp: See CA-2374
#   * cert-str34-c
#   * hicpp-avoid-c-arrays
#   * hicpp-avoid-goto
#   * hicpp-deprecated-headers
#   * hicpp-explicit-conversions
#   * hicpp-function-size
#   * hicpp-invalid-access-moved
#   * hicpp-member-init
#   * hicpp-move-const-arg
#   * hicpp-multiway-paths-covered
#   * hicpp-no-array-decay
#   * hicpp-noexcept-move
#   * hicpp-no-malloc
#   * hicpp-signed-bitwise
#   * hicpp-special-member-functions
#   * hicpp-uppercase-literal-suffix
#   * hicpp-use-auto
#   * hicpp-use-emplace
#   * hicpp-use-equals-default
#   * hicpp-use-equals-delete
#   * hicpp-use-nullptr
#   * hicpp-use-override
#   * hicpp-vararg
#   * llvm-else-after-return
#   * llvm-include-order
#   * llvm-header-guard
#   * llvm-namespace-comment
#   * llvm-twine-local: See CA-2567
#   * llvm-qualified-auto
#   * misc-definitions-in-headers
#   * misc-forwarding-reference-overload  # Wait for C++14 enable_if_t?
#   * misc-non-private-member-variables-in-classes
#   * misc-string-compare
#   * misc-unconventional-assign-operator
#   * modernize-avoid-bind
#   * modernize-avoid-c-arrays
#   * modernize-deprecated-headers
#   * modernize-loop-convert
#   * modernize-make-unique
#   * modernize-pass-by-value
#   * modernize-redundant-void-arg
#   * modernize-return-braced-init-list
#   * modernize-use-auto
#   * modernize-use-bool-literals
#   * modernize-use-default-member-init
#   * modernize-use-emplace
#   * modernize-use-equals-default
#   * modernize-use-equals-delete
#   * modernize-use-nullptr
#   * modernize-use-override
#   * modernize-use-trailing-return-type
#   * modernize-use-using
#   * performance-move-const-arg
#   * performance-move-constructor-init
#   * performance-noexcept-move-constructor
#   * performance-unnecessary-value-param
#   * readability-avoid-const-params-in-decls
#   * readability-const-return-type
#   * readability-container-size-empty
#   * readability-convert-member-functions-to-static,
#   * readability-delete-null-pointer
#   * readability-else-after-return
#   * readability-function-size
#   * readability-implicit-bool-conversion
#   * readability-inconsistent-declaration-parameter-name
#   * readability-isolate-declaration
#   * readability-non-const-parameter
#   * readability-qualified-auto
#   * readability-redundant-control-flow
#   * readability-redundant-smartptr-get
#   * readability-redundant-string-cstr
#   * readability-redundant-string-init
#   * readability-simplify-boolean-expr
#   * readability-static-accessed-through-instance
#   * readability-static-definition-in-anonymous-namespace
#   * readability-string-compare
#   * readability-uppercase-literal-suffix
#   * readability-use-anyofallof
Checks: "bugprone-*,\
         -bugprone-branch-clone,\
         -bugprone-easily-swappable-parameters,\
         -bugprone-forwarding-reference-overload,\
         -bugprone-macro-parentheses,\
         -bugprone-narrowing-conversions,\
         -bugprone-not-null-terminated-result,\
         -bugprone-parent-virtual-call,\
         -bugprone-signed-char-misuse,\
         -bugprone-sizeof-expression,\
         -bugprone-reserved-identifier,\
         -bugprone-too-small-loop-variable,\
         -bugprone-use-after-move,\
         cert-*,\
         -cert-dcl21-cpp,\
         -cert-dcl37-c,\
         -cert-dcl51-cpp,\
         -cert-dcl59-cpp,\
         -cert-err34-c,\
         -cert-err58-cpp,\
         -cert-flp30-c,\
         -cert-msc30-c,\
         -cert-msc32-c,\
         -cert-msc50-cpp,\
         -cert-msc51-cpp,\
         -cert-oop11-cpp,\
         -cert-oop54-cpp,\
         -cert-str34-c,\
         clang-diagnostic-*,\
         -clang-diagnostic-deprecated-declarations,\
         -clang-diagnostic-typedef-redefinition,\
         clang-analyzer-*,\
         -clang-analyzer-cplusplus.NewDelete,\
         -clang-analyzer-cplusplus.NewDeleteLeaks,\
         -clang-analyzer-optin.performance.Padding,\
         -clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,\
         *googletest*,\
         -google-readability-avoid-underscore-in-googletest-name,\
         concurrency-*,\
         -concurrency-mt-unsafe,\
         hicpp-*,\
         -hicpp-avoid-c-arrays,\
         -hicpp-avoid-goto,\
         -hicpp-deprecated-headers,\
         -hicpp-explicit-conversions,\
         -hicpp-function-size,\
         -hicpp-invalid-access-moved,\
         -hicpp-member-init,\
         -hicpp-move-const-arg,\
         -hicpp-multiway-paths-covered,\
         -hicpp-named-parameter,\
         -hicpp-no-array-decay,\
         -hicpp-noexcept-move,\
         -hicpp-no-malloc,\
         -hicpp-signed-bitwise,\
         -hicpp-special-member-functions,\
         -hicpp-uppercase-literal-suffix,\
         -hicpp-use-auto,\
         -hicpp-use-emplace,\
         -hicpp-use-equals-default,\
         -hicpp-use-equals-delete,\
         -hicpp-use-nullptr,\
         -hicpp-use-override,\
         -hicpp-vararg,\
         llvm-*,\
         -llvm-else-after-return,\
         -llvm-include-order,\
         -llvm-header-guard,\
         -llvm-namespace-comment,\
         -llvm-twine-local,\
         -llvm-qualified-auto,\
         misc-*,\
         -misc-definitions-in-headers,\
         -misc-forwarding-reference-overload,\
         -misc-include-cleaner,\
         -misc-macro-parentheses,\
         -misc-misplaced-const,\
         -misc-non-private-member-variables-in-classes,\
         -misc-no-recursion,\
         -misc-redundant-expression,\
         -misc-string-compare,\
         -misc-unconventional-assign-operator,\
         -misc-unused-parameters,\
         -misc-use-anonymous-namespace,\
         modernize-*,\
         -modernize-avoid-bind,\
         -modernize-avoid-c-arrays,\
         -modernize-concat-nested-namespaces,\
         -modernize-deprecated-headers,\
         -modernize-loop-convert,\
         -modernize-macro-to-enum,\
         -modernize-make-unique,\
         -modernize-pass-by-value,\
         -modernize-redundant-void-arg,\
         -modernize-return-braced-init-list,\
         -modernize-use-auto,\
         -modernize-use-bool-literals,\
         -modernize-use-default-member-init,\
         -modernize-use-emplace,\
         -modernize-use-equals-default,\
         -modernize-use-equals-delete,\
         -modernize-use-nodiscard,\
         -modernize-use-nullptr,\
         -modernize-use-override,\
         -modernize-use-trailing-return-type,\
         -modernize-use-using,\
         performance-*,\
         -performance-move-const-arg,\
         -performance-move-constructor-init,\
         -performance-noexcept-move-constructor,\
         -performance-no-int-to-ptr,\
         -performance-unnecessary-value-param,\
         portability-*,\
         readability-*,\
         -readability-avoid-const-params-in-decls,\
         -readability-const-return-type,\
         -readability-container-size-empty,\
         -readability-convert-member-functions-to-static,
         -readability-delete-null-pointer,\
         -readability-else-after-return,\
         -readability-function-cognitive-complexity,\
         -readability-function-size,\
         -readability-implicit-bool-conversion,\
         -readability-inconsistent-declaration-parameter-name,\
         -readability-isolate-declaration,\
         -readability-magic-numbers,\
         -readability-make-member-function-const,\
         -readability-named-parameter,\
         -readability-non-const-parameter,\
         -readability-qualified-auto,\
         -readability-redundant-control-flow,\
         -readability-redundant-member-init,\
         -readability-redundant-smartptr-get,\
         -readability-redundant-string-cstr,\
         -readability-redundant-string-init,\
         -readability-simplify-boolean-expr,\
         -readability-static-accessed-through-instance,\
         -readability-static-definition-in-anonymous-namespace,\
         -readability-string-compare,\
         -readability-uppercase-literal-suffix,\
         -readability-use-anyofallof"

# -UNDEBUG so that clang-tidy always sees asserts, whatever the build type.
# -fno-caret-diagnostics to silence warning counts from headers.
# -Wno-unknown-warning-option so we can use compilation database on GCC configs
# -Wno-return-type-c-linkage so we can export functions that return C++ types using C linkage.
ExtraArgs: [
    '-UNDEBUG',
    '-fno-caret-diagnostics',
    '-Wno-unknown-warning-option',
    '-Wno-return-type-c-linkage'
]
WarningsAsErrors: '*'
HeaderFilterRegex: '.*'
AnalyzeTemporaryDtors: false
FormatStyle:     'file'
CheckOptions:
  - key:             readability-braces-around-statements.ShortStatementLines
    value:           '1'
  - key:             hicpp-braces-around-statements.ShortStatementLines
    value:           '1'
  - key:             readability-function-size.StatementThreshold
    value:           '800'
  - key:             google-readability-namespace-comments.ShortNamespaceLines
    value:           '10'
  - key:             google-readability-namespace-comments.SpacesBeforeComments
    value:           '2'
  - key:             modernize-loop-convert.MaxCopySize
    value:           '16'
  - key:             modernize-loop-convert.MinConfidence
    value:           reasonable
  - key:             modernize-loop-convert.NamingStyle
    value:           CamelCase
  - key:             modernize-pass-by-value.IncludeStyle
    value:           llvm
  - key:             modernize-replace-auto-ptr.IncludeStyle
    value:           llvm
  - key:             modernize-use-nullptr.NullMacros
    value:           'NULL'
  - key:             modernize-use-transparent-functors.SafeMode
    value:           '1'
  - key:             readability-redundant-access-specifiers.CheckFirstDeclaration
    value:           '1'
  - key:             readability-identifier-length.MinimumParameterNameLength
    value:           '1'
  - key:             readability-identifier-length.MinimumVariableNameLength
    value:           '1'
  - key:             readability-identifier-length.MinimumLoopCounterNameLength
    value:           '1'
...