tidy - bugprone-invalid-enum-default-initialization — Extra Clang Tools 22.0.0git documentation (original) (raw)

Detects default initialization (to 0) of variables with enum type where the enum has no enumerator with value of 0.

In C++ a default initialization is performed if a variable is initialized with initializer list or in other implicit ways, and no value is specified at the initialization. In such cases the value 0 is used for the initialization. This also applies to enumerations even if it does not have an enumerator with value 0. In this way a variable with the enum type may contain initially an invalid value (if the program expects that it contains only the listed enumerator values).

The check emits a warning only if an enum variable is default-initialized (contrary to not initialized) and the enum does not have an enumerator with value of 0. The type can be a scoped or non-scoped enum. Unions are not handled by the check (if it contains a member of enumeration type).

Note that the enum std::errc is always ignored because it is expected to be default initialized, despite not defining an enumerator with the value 0.

enum class Enum1: int { A = 1, B };

enum class Enum0: int { A = 0, B };

void f() { Enum1 X1{}; // warn: 'X1' is initialized to 0 Enum1 X2 = Enum1(); // warn: 'X2' is initialized to 0 Enum1 X3; // no warning: 'X3' is not initialized Enum0 X4{}; // no warning: type has an enumerator with value of 0 }

struct S1 { Enum1 A; S(): A() {} // warn: 'A' is initialized to 0 };

struct S2 { int A; Enum1 B; };

S2 VarS2{}; // warn: member 'B' is initialized to 0

The check applies to initialization of arrays or structures with initialization lists in C code too. In these cases elements not specified in the list (and have enum type) are set to 0.

enum Enum1 { Enum1_A = 1, Enum1_B }; struct Struct1 { int a; enum Enum1 b; };

enum Enum1 Array1[2] = {Enum1_A}; // warn: omitted elements are initialized to 0 enum Enum1 Array2[2][2] = {{Enum1_A}, {Enum1_A}}; // warn: last element of both nested arrays is initialized to 0 enum Enum1 Array3[2][2] = {{Enum1_A, Enum1_A}}; // warn: elements of second array are initialized to 0

struct Struct1 S1 = {1}; // warn: element 'b' is initialized to 0

Options¶

IgnoredEnums¶

Semicolon-separated list of regexes specifying enums for which this check won’t be enforced. Default is ::std::errc.