# Extra Clang Tools 4 documentation

## clang-tidy - cppcoreguidelines-pro-type-member-init

# cppcoreguidelines-pro-type-member-init

The check flags user-defined constructor definitions that do not initialize all fields that would be left in an undefined state by default construction, e.g. builtins, pointers and record types without user-provided default constructors containing at least one such type. If these fields aren’t initialized, the constructor will leave some of the memory in an undefined state.

For C++11 it suggests fixes to add in-class field initializers. For older versions it inserts the field initializers into the constructor initializer list. It will also initialize any direct base classes that need to be zeroed in the constructor initializer list.

The check takes assignment of fields in the constructor body into account but generates false positives for fields initialized in methods invoked in the constructor body.

The check also flags variables with automatic storage duration that have record types without a user-provided constructor and are not initialized. The suggested fix is to zero initialize the variable via `{}` for C++11 and beyond or `= {}` for older language versions.

## Options

`IgnoreArrays```

  If set to non-zero, the check will not warn about array members that are not zero-initialized during construction. For performance critical code, it may be important to not initialize fixed-size array members. Default is 0.

This rule is part of the “Type safety” profile of the C++ Core Guidelines, corresponding to rule Type.6. See https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Pro-type-memberinit.