# Extra Clang Tools 22.1.2 documentation

## clang-tidy - modernize-avoid-c-arrays

# modernize-avoid-c-arrays

cppcoreguidelines-avoid-c-arrays redirects here as an alias for this check.

hicpp-avoid-c-arrays redirects here as an alias for this check.

Finds C-style array types and recommend to use `std::array<>` / `std::vector<>`. All types of C arrays are diagnosed.

For parameters of incomplete C-style array type, it would be better to use `std::span` / `gsl::span` as replacement.

However, fix-it are potentially dangerous in header files and are therefore not emitted right now.

    int a[] = {1, 2}; // warning: do not declare C-style arrays, use 'std::array' instead

    int b[1]; // warning: do not declare C-style arrays, use 'std::array' instead

    void foo() {
      int c[b[0]]; // warning: do not declare C VLA arrays, use 'std::vector' instead
    }

    template <typename T, int Size>
    class array {
      T d[Size]; // warning: do not declare C-style arrays, use 'std::array' instead

      int e[1]; // warning: do not declare C-style arrays, use 'std::array' instead
    };

    array<int[4], 2> d; // warning: do not declare C-style arrays, use 'std::array' instead

    using k = int[4]; // warning: do not declare C-style arrays, use 'std::array' instead

However, the `extern "C"` code is ignored, since it is common to share such headers between C code, and C++ code.

    // Some header
    extern "C" {

    int f[] = {1, 2}; // not diagnosed

    int j[1]; // not diagnosed

    inline void bar() {
      {
        int j[j[0]]; // not diagnosed
      }
    }

    }

Similarly, the `main()` function is ignored. Its second and third parameters can be either `char* argv[]` or `char** argv`, but cannot be `std::array<>`.

## Options

AllowStringArrays

  When set to true (default is false), variables of character array type with deduced length, initialized directly from string literals, will be ignored. This option doesn’t affect cases where length can’t be deduced, resembling pointers, as seen in class members and parameters. Example:

      const char name[] = "Some name";