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  1. Rules Repository
  2. RSPEC-5827

"auto" should be used to avoid repetition of types

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    Details

    • Default Severity:
      Major
    • Impact:
      Low
    • Likelihood:
      High
    • Default Quality Profiles:
      Sonar way, MISRA C++ 2008 recommended
    • Covered Languages:
      C++
    • Irrelevant for Languages:
      ABAP, APEX, C#, C, Cobol, CSS, Flex, Go, HTML, Java, JavaScript, Kotlin, Objective-C, PHP, PL/I, PL/SQL, Python, RPG, Ruby, Rust, Scala, Solidity, Swift, T-SQL, TypeScript, VB.Net, VB6, XML
    • Remediation Function:
      Constant/Issue
    • Constant Cost:
      2min
    • Analysis Scope:
      Main Sources, Test Sources
    • CppCoreGuidelines:
      ES.11

      Description

      When used as a type specifier in a declaration, auto allows the compiler to deduce the type of a variable based on the type of the initialization expression.

      When the spelling of the initialization expression already contains the type of the declared variable, it leaves no ambiguity and auto should be used as it makes the code easier to read and reduces duplication. This includes initializations using new, template factory functions for smart pointers and cast expressions.

      Noncompliant Code Example

      #include <memory>
#include <vector>

class C {};
class LongAndBoringClassName : public C {};

void f() {
  LongAndBoringClassName *newClass1 = new LongAndBoringClassName(); // Noncompliant
  LongAndBoringClassName *newClass2 = new LongAndBoringClassName(); // Noncompliant

  std::unique_ptr<LongAndBoringClassName> newClass3 = std::make_unique<LongAndBoringClassName>(); // Noncompliant
  std::shared_ptr<LongAndBoringClassName> newClass4 = std::make_shared<LongAndBoringClassName>(); // Noncompliant

  C* c = new LongAndBoringClassName(); // Compliant
  LongAndBoringClassName *newClass5 = static_cast<LongAndBoringClassName*>(c); // Noncompliant
}

      Compliant Solution

      #include <memory>
#include <vector>

class C {};
class LongAndBoringClassName : public C {};

void f() {
  auto newClass1 = new LongAndBoringClassName(); // Compliant
  auto *newClass2 = new LongAndBoringClassName(); // Compliant

  auto newClass3 = std::make_unique<LongAndBoringClassName>(); // Compliant
  auto newClass4 = std::make_shared<LongAndBoringClassName>(); // Compliant

  C* c = new LongAndBoringClassName(); // Compliant
  auto newClass5 = static_cast<LongAndBoringClassName*>(c); // Compliant
}

      See

        Attachments

          Issue Links

          is implemented by

          New Feature - A new feature of the product, which has yet to be developed. CPP-1437 Rule S5827: "auto" should be used to avoid repetition of types

          • Major - Major loss of function.
          • Closed
          is related to

          Improvement - An improvement or enhancement to an existing feature or task. CPP-2956 S5827: Using a concept auto for a variable should not trigger the rule

          • Major - Major loss of function.
          • Closed

          False-Positive - Unexpected issue reported by a rule CPP-2792 S5827: Fix false positive with macros

          • Major - Major loss of function.
          • Open

          False Negative - True issue, expected to be covered by a rule, but ultimately not reported CPP-3086 S5827: Fix false-negative on parenthesized expression in initializer

          • Major - Major loss of function.
          • Closed

          False Negative - True issue, expected to be covered by a rule, but ultimately not reported CPP-3253 S5827: False negative for list-initialized objects

          • Major - Major loss of function.
          • Closed

          Code Smell Detection - RSPEC-6234 "auto" should be used to store a result of functions that conventionally return an iterator

          • Active
          relates to

          New Feature - A new feature of the product, which has yet to be developed. CPP-2682 Rule S6234: "auto" should be used to store a result of functions that conventionally return an iterator

          • Major - Major loss of function.
          • Closed

            Activity

              People

              Assignee:
              Unassigned Unassigned
              Reporter:
              geoffray.adde Geoffray Adde
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                Dates

                Created:
                Updated: