[clang-tidy] Ignore vector<bool> in inefficient-vector-operation.

[alexfh]

Should we look at whether the size is statically known?

[alexfh]

In D35787#819007, @alexfh wrote:

Should we look at whether the size is statically known?

(and small enough)

[hokein]

In D35787#819007, @alexfh wrote:

Should we look at whether the size is statically known?

Do you mean the size of the template type T in vector<T>? STL only provides a template specialization for std::vector<bool>, so I think excluding vector<bool> is probably enough, or am I missing anything here?

[alexfh]

In D35787#830351, @hokein wrote:

In D35787#819007, @alexfh wrote:

Should we look at whether the size is statically known?

Do you mean the size of the template type T in vector<T>? STL only provides a template specialization for std::vector<bool>, so I think excluding vector<bool> is probably enough, or am I missing anything here?

I meant the size of the vector, i.e. the number of elements that is going to be pushed into it. Is it still reasonable to exempt vector<bool>, if, say, a million of bools is pushed into it?

clang-tidy/performance/InefficientVectorOperationCheck.cpp

 
 void InefficientVectorOperationCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "VectorLikeClasses",
                 utils::options::serializeStringList(VectorLikeClasses));
 }
 
 void InefficientVectorOperationCheck::registerMatchers(MatchFinder *Finder) {
-  const auto VectorDecl = cxxRecordDecl(hasAnyName(SmallVector<StringRef, 5>(
-      VectorLikeClasses.begin(), VectorLikeClasses.end())));
+  const auto VectorDecl = classTemplateSpecializationDecl(
+      hasAnyName(SmallVector<StringRef, 5>(VectorLikeClasses.begin(),
+                                           VectorLikeClasses.end())),
+      // Exclude std::vector<bool>: STL provides a specilaization of std::vector
+      // for the type "bool", which may be optimized for space efficiency (e.g.
+      // each element occupies a single bit instead of sizeof(bool) bytes).
+      unless(hasTemplateArgument(0, refersToType(booleanType()))));
   const auto VectorDefaultConstructorCall = cxxConstructExpr(
       hasType(VectorDecl),
       hasDeclaration(cxxConstructorDecl(isDefaultConstructor())));
   const auto VectorVarDecl =
       varDecl(hasInitializer(VectorDefaultConstructorCall))
           .bind(VectorVarDeclName);
   const auto VectorAppendCallExpr =
       cxxMemberCallExpr(

test/clang-tidy/performance-inefficient-vector-operation.cpp

// ---- Non-fixed Cases ----
     std::vector<int>* z13 = &t;
     // We only support detecting the range init expression which references
     // container directly.
     // Complex range init expressions like `*z13` is not supported.
     for (const auto &e : *z13) {
       z12.push_back(e);
     }
   }
+  {
+    std::vector<bool> z14;
+    // std::vector<bool> will be ignored as STL provides a possibly
+    // space-efficient specilaization of std::vector for the type "bool".
+    for (int i = 0; i < 10; ++i) {
+      z14.push_back(true);
+    }
+  }
 }