[style, fix] add clang-tidy; fix some warnings about them

.clang-tidy

@@ -0,0 +1,44 @@
+Checks: |
+  *
+  -readability-*
+  -llvmlibc-*
+
+  -altera-id-dependent-backward-branch
+  -altera-struct-pack-align
+  -altera-unroll-loops
+  -bugprone-branch-clone
+  -bugprone-easily-swappable-parameters
+  -bugprone-reserved-identifier
+  -cert-dcl37-c
+  -cert-dcl51-cpp
+  -clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling
+  -cppcoreguidelines-avoid-magic-numbers
+  -cppcoreguidelines-init-variables
+  -eadability-avoid-unconditional-preprocessor-if
+  -google-readability-braces-around-statements
+  -hicpp-braces-around-statements
+  -hicpp-signed-bitwise
+  -hicpp-uppercase-literal-suffix
+  -llvm-else-after-return
+  -llvm-header-guard
+  -misc-confusable-identifiers
+  -misc-no-recursion
+
+  -bugprone-unhandled-self-assignment
+  -cert-oop54-cpp
+  -cppcoreguidelines-avoid-c-arrays
+  -cppcoreguidelines-avoid-const-or-ref-data-members
+  -cppcoreguidelines-pro-bounds-array-to-pointer-decay
+  -cppcoreguidelines-pro-type-member-init
+  -cppcoreguidelines-pro-type-reinterpret-cast
+  -fuchsia-default-arguments-calls
+  -fuchsia-default-arguments-declarations
+  -fuchsia-overloaded-operator
+  -google-explicit-constructor
+  -hicpp-avoid-c-arrays
+  -hicpp-explicit-conversions
+  -hicpp-member-init
+  -hicpp-no-array-decay
+  -modernize-avoid-c-arrays
+  -modernize-use-nodiscard
+  -modernize-use-trailing-return-type