literal (C++ Component Extensions)
The latest version of this topic can be found at literal (C++ Component Extensions).
A variable (data member) marked as literal in a /clr compilation is the native equivalent of a static const variable.
All Platforms
Remarks
(There are no remarks for this language feature that apply to all runtimes.)
Windows Runtime
Remarks
(There are no remarks for this language feature that apply to only the Windows Runtime.)
Requirements
Compiler option: /ZW
Common Language Runtime
Remarks
A data member marked as literalmust be initialized when declared and the value must be a constant integral, enum, or string type. Conversion from the type of the initialization expression to the type of the static const data-member must not require a user-defined conversion.
No memory is allocated for the literal field at runtime; the compiler only inserts its value in the metadata for the class.
A variable marked static const will not be available in metadata to other compilers.
For more information, see Static and const.
literal is a context-sensitive keyword. See Context-Sensitive Keywords for more information.
Example
This example shows that a literal variable implies static.
// mcppv2_literal.cpp
// compile with: /clr
ref struct X {
literal int i = 4;
};
int main() {
int value = X::i;
}
Example
The following sample shows the affect of literal in metadata:
// mcppv2_literal2.cpp
// compile with: /clr /LD
public ref struct A {
literal int lit = 0;
static const int sc = 1;
};
Notice the difference in the metadata for sc and lit: the modopt directive is applied to sc, meaning it can be ignored by other compilers.
.field public static int32 modopt
([mscorlib]System.Runtime.CompilerServices.IsConst) sc = int32
(0x0000000A)
.field public static literal int32 lit = int32
(0x0000000A)
Example
The following sample, authored in C#, references the metadata created in the previous sample and shows the affect of literal and static const variables:
// mcppv2_literal3.cs
// compile with: /reference:mcppv2_literal2.dll
// A C# program
class B {
public static void Main() {
// OK
System.Console.WriteLine(A.lit);
System.Console.WriteLine(A.sc);
// C# does not enforce C++ const
A.sc = 9;
System.Console.WriteLine(A.sc);
// C# enforces const for a literal
A.lit = 9; // CS0131
// you can assign a C++ literal variable to a C# const variable
const int i = A.lit;
System.Console.WriteLine(i);
// but you cannot assign a C++ static const variable
// to a C# const variable
const int j = A.sc; // CS0133
System.Console.WriteLine(j);
}
}
Requirements
Compiler option: /clr