2.8 Special Enums ¶

Special enum names are used to represent types that do not have an equivalent basic D type. For example, C++ types used by the C++ name mangler.

Special enums are declared opaque, with a base type explicitly set. Unlike regular opaque enums, special enums can be used as any other value type. They have a default .init value, as well as other enum properties available (.min, .max). Special enums can be declared in any module, and will be recognized by the compiler.

import gcc.builtins;
enum __c_long : __builtin_clong;
__c_long var = 0x800A;

The following identifiers are recognized by GNU D.

__c_complex_double

C _Complex double type.

__c_complex_float

C _Complex float type.

__c_complex_real

C _Complex long double type.

__c_long

C++ long type.

__c_longlong

C++ long long type.

__c_long_double

C long double type.

__c_ulong

C++ unsigned long type.

__c_ulonglong

C++ unsigned long long type.

__c_wchar_t

C++ wchar_t type.

The core.stdc.config module declares the following shorthand alias types for convenience: c_complex_double, c_complex_float, c_complex_real, cpp_long, cpp_longlong, c_long_double, cpp_ulong, cpp_ulonglong.

It may cause undefined behavior at runtime if a special enum is declared with a base type that has a different size to the target C/C++ type it is representing. The GNU D compiler will catch such declarations and emit a warning when the -Wmismatched-special-enum option is seen on the command-line.