modernize-use-designated-initializers

Finds initializer lists for aggregate types which could be written as designated initializers instead.

With plain initializer lists, it is very easy to introduce bugs when adding new fields in the middle of a struct or class type. The same confusion might arise when changing the order of fields.

C++20 supports the designated initializer syntax for aggregate types. By applying it, we can always be sure that aggregates are constructed correctly, because every variable being initialized is referenced by its name.

Example:

struct S { int i, j; };

is an aggregate type that should be initialized as

S s{.i = 1, .j = 2};

instead of

S s{1, 2};

which could easily become an issue when i and j are swapped in the declaration of S.

Even when compiling in a language version older than C++20, depending on your compiler, designated initializers are potentially supported. Therefore, the check is by default restricted to C99/C++20 and above. Check out the options -Wc99-designator to get support for mixed designators in initializer list in C and -Wc++20-designator for support of designated initializers in older C++ language modes.

Options

IgnoreMacros

The value false specifies that components of initializer lists expanded from macros are not checked. Default is true.

IgnoreSingleElementAggregates

The value false specifies that even initializers for aggregate types with only a single element should be checked. std::array initializations are always excluded, as the type is a standard library abstraction and not intended to be initialized with designated initializers. Default is true.

RestrictToPODTypes

The value true specifies that only Plain Old Data (POD) types shall be checked. This makes the check applicable to even older C++ standards. Default is false.

StrictCStandardCompliance

When set to false, the check will not restrict itself to C99 and above. Default is true.

StrictCppStandardCompliance

When set to false, the check will not restrict itself to C++20 and above. Default is true.