Add .clang-tidy and fix clang-tidy warnings (rapidsai#857)

Adds a .clang-tidy configuration file.   This does not add CI tests yet, but I wanted to get it ready to do so without forcing it on anyone. As-is, this PR will enable clang-tidy "yellow squiggles" if you use clangd in vscode.

Starting with these Checks:

```
Checks:          'clang-diagnostic-*,
                  clang-analyzer-*,
                  cppcoreguidelines-*,
                  modernize-*,
                  bugprone-*,
                  performance-*,
                  readability-*,
                  llvm-*,
                  -modernize-use-trailing-return-type'
``` 

Here is a list of warnings fixed

* readability-identifier-length
* cppcoreguidelines-special-member-functions
* modernize-use-nodiscard
* modernize-use-nullptr
* cppcoreguidelines-pro-type-cstyle-cast (ignore locally for CUDA-defined stream constants)
* performance-noexcept-move-constructor
* readability-function-cognitive-complexity
* readability-qualified-auto
* modernize-concat-nested-namespaces
* readability-isolate-declaration
* readability-redundant-member-init
* modernize-use-override
* modernize-avoid-c-arrays
* cppcoreguidelines-pro-bounds-array-to-pointer-decay
* cppcoreguidelines-pro-bounds-constant-array-index
* bugprone-narrowing-conversions
* readability-implicit-bool-conversion
* readability-redundant-smartptr-get
* llvm-else-after-return
* readability-uppercase-literal-suffix
* readability-braces-around-statements
* cppcoreguidelines-avoid-magic-numbers
* performance-unnecessary-value-param
* bugprone-macro-parentheses
* performance-faster-string-find

NOLINT lines have been added where fixes are unavailable, such as with necessary pointer arithmetic or `reinterpret_cast` calls.

I have a private branch of google test which adds NOLINT lines to suppress warnings caused by gtest's code. I plan to make a PR for this.

There are still a couple of outstanding warnings having to do with "easily swappable parameters" (e.g. when a function takes two sizes.  Fixing these requires breaking API changes. Alternatively we could suppress them.)

Authors:
  - Mark Harris (https://github.com/harrism)

Approvers:
  - Jake Hemstad (https://github.com/jrhemstad)
  - Rong Ou (https://github.com/rongou)
  - GALI PREM SAGAR (https://github.com/galipremsagar)

URL: rapidsai#857

Author: harrism

.clang-tidy

@@ -0,0 +1,67 @@
+---
+Checks:          'clang-diagnostic-*,
+                  clang-analyzer-*,
+                  cppcoreguidelines-*,
+                  modernize-*,
+                  bugprone-*,
+                  performance-*,
+                  readability-*,
+                  llvm-*,
+                  -cppcoreguidelines-macro-usage,
+                  -llvm-header-guard,
+                  -modernize-use-trailing-return-type,
+                  -readability-named-parameter'
+WarningsAsErrors: ''
+HeaderFilterRegex: ''
+AnalyzeTemporaryDtors: false
+FormatStyle:     none
+CheckOptions:
+  - key:             cert-dcl16-c.NewSuffixes
+    value:           'L;LL;LU;LLU'
+  - key:             cert-oop54-cpp.WarnOnlyIfThisHasSuspiciousField
+    value:           '0'
+  - key:             cert-str34-c.DiagnoseSignedUnsignedCharComparisons
+    value:           '0'
+  - key:             cppcoreguidelines-explicit-virtual-functions.IgnoreDestructors
+    value:           '1'
+  - key:             cppcoreguidelines-non-private-member-variables-in-classes.IgnoreClassesWithAllMemberVariablesBeingPublic
+    value:           '1'
+  - key:             google-readability-braces-around-statements.ShortStatementLines
+    value:           '1'
+  - key:             google-readability-function-size.StatementThreshold
+    value:           '800'
+  - key:             google-readability-namespace-comments.ShortNamespaceLines
+    value:           '10'
+  - key:             google-readability-namespace-comments.SpacesBeforeComments
+    value:           '2'
+  - key:             llvm-else-after-return.WarnOnConditionVariables
+    value:           '0'
+  - key:             llvm-else-after-return.WarnOnUnfixable
+    value:           '0'
+  - key:             llvm-qualified-auto.AddConstToQualified
+    value:           '0'
+  - 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:             readability-identifier-length.IgnoredParameterNames
+    value:           'mr|os'
+  - key:             readability-identifier-length.IgnoredVariableNames
+    value:           'mr|_'
+  #- key:             readability-function-cognitive-complexity.IgnoreMacros
+  #  value:           '1'
+  - key:             bugprone-easily-swappable-parameters.IgnoredParameterNames
+    value:           'alignment'
+  - key:             cppcoreguidelines-avoid-magic-numbers.IgnorePowersOf2IntegerValues
+    value:           '1'
+  - key:             readability-magic-numbers.IgnorePowersOf2IntegerValues
+    value:           '1'
+...

benchmarks/cuda_stream_pool/cuda_stream_pool_bench.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, NVIDIA CORPORATION.
+ * Copyright (c) 2020-2021, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,36 +14,36 @@
  * limitations under the License.
  */
 
-#include <benchmark/benchmark.h>
-
 #include <rmm/cuda_stream_pool.hpp>
 #include <rmm/detail/error.hpp>
 
 #include <cuda_runtime_api.h>
 
+#include <benchmark/benchmark.h>
+
 #include <stdexcept>
 
 static void BM_StreamPoolGetStream(benchmark::State& state)
 {
   rmm::cuda_stream_pool stream_pool{};
 
-  for (auto _ : state) {
-    auto s = stream_pool.get_stream();
-    cudaStreamQuery(s.value());
+  for (auto _ : state) {  // NOLINT(clang-analyzer-deadcode.DeadStores)
+    auto stream = stream_pool.get_stream();
+    cudaStreamQuery(stream.value());
   }
 
-  state.SetItemsProcessed(state.iterations());
+  state.SetItemsProcessed(static_cast<int64_t>(state.iterations()));
 }
 BENCHMARK(BM_StreamPoolGetStream)->Unit(benchmark::kMicrosecond);
 
 static void BM_CudaStreamClass(benchmark::State& state)
 {
-  for (auto _ : state) {
-    auto s = rmm::cuda_stream{};
-    cudaStreamQuery(s.view().value());
+  for (auto _ : state) {  // NOLINT(clang-analyzer-deadcode.DeadStores)
+    auto stream = rmm::cuda_stream{};
+    cudaStreamQuery(stream.view().value());
   }
 
-  state.SetItemsProcessed(state.iterations());
+  state.SetItemsProcessed(static_cast<int64_t>(state.iterations()));
 }
 BENCHMARK(BM_CudaStreamClass)->Unit(benchmark::kMicrosecond);
 

benchmarks/device_uvector/device_uvector_bench.cu

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, NVIDIA CORPORATION.
+ * Copyright (c) 2020-2021, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,33 +14,35 @@
  * limitations under the License.
  */
 
-#include <benchmark/benchmark.h>
-
-#include <cuda_runtime_api.h>
 #include <rmm/device_uvector.hpp>
 #include <rmm/device_vector.hpp>
 #include <rmm/mr/device/cuda_memory_resource.hpp>
 #include <rmm/mr/device/per_device_resource.hpp>
 #include <rmm/mr/device/pool_memory_resource.hpp>
 
+#include <benchmark/benchmark.h>
+
+#include <cuda_runtime_api.h>
+
 static void BM_UvectorSizeConstruction(benchmark::State& state)
 {
   rmm::mr::cuda_memory_resource cuda_mr{};
   rmm::mr::pool_memory_resource<rmm::mr::cuda_memory_resource> mr{&cuda_mr};
   rmm::mr::set_current_device_resource(&mr);
 
-  for (auto _ : state) {
+  for (auto _ : state) {  // NOLINT(clang-analyzer-deadcode.DeadStores)
     rmm::device_uvector<int32_t> vec(state.range(0), rmm::cuda_stream_view{});
     cudaDeviceSynchronize();
   }
 
-  state.SetItemsProcessed(state.iterations());
+  state.SetItemsProcessed(static_cast<int64_t>(state.iterations()));
 
   rmm::mr::set_current_device_resource(nullptr);
 }
+
 BENCHMARK(BM_UvectorSizeConstruction)
-  ->RangeMultiplier(10)
-  ->Range(10'000, 1'000'000'000)
+  ->RangeMultiplier(10)           // NOLINT
+  ->Range(10'000, 1'000'000'000)  // NOLINT
   ->Unit(benchmark::kMicrosecond);
 
 static void BM_ThrustVectorSizeConstruction(benchmark::State& state)
@@ -49,19 +51,19 @@ static void BM_ThrustVectorSizeConstruction(benchmark::State& state)
   rmm::mr::pool_memory_resource<rmm::mr::cuda_memory_resource> mr{&cuda_mr};
   rmm::mr::set_current_device_resource(&mr);
 
-  for (auto _ : state) {
+  for (auto _ : state) {  // NOLINT(clang-analyzer-deadcode.DeadStores)
     rmm::device_vector<int32_t> vec(state.range(0));
     cudaDeviceSynchronize();
   }
 
-  state.SetItemsProcessed(state.iterations());
+  state.SetItemsProcessed(static_cast<int64_t>(state.iterations()));
 
   rmm::mr::set_current_device_resource(nullptr);
 }
 
 BENCHMARK(BM_ThrustVectorSizeConstruction)
-  ->RangeMultiplier(10)
-  ->Range(10'000, 1'000'000'000)
+  ->RangeMultiplier(10)           // NOLINT
+  ->Range(10'000, 1'000'000'000)  // NOLINT
   ->Unit(benchmark::kMicrosecond);
 
 BENCHMARK_MAIN();