IsLong Class
Definition
Important
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Indicates that a modified integer is a standard C++ long
value. This class cannot be inherited.
public ref class IsLong abstract sealed
public static class IsLong
type IsLong = class
Public Class IsLong
- Inheritance
-
IsLong
Examples
The following example demonstrates how to emit an IsLong object into an assembly using reflection.
#using <mscorlib.dll>
using namespace System;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
using namespace System::Runtime::CompilerServices;
using namespace System::Threading;
ref class CodeEmitter
{
private:
AssemblyBuilder^ asmBuilder;
String^ asmName;
ModuleBuilder^ modBuilder;
void prepareAssembly(String^ name){
// Check the input.
if(!name){
throw gcnew ArgumentNullException("AssemblyName");
}
asmName = name;
// Create an AssemblyName object and set the name.
AssemblyName^ asmName = gcnew AssemblyName();
asmName->Name = name;
// Use the AppDomain class to create an AssemblyBuilder instance.
AppDomain^ currentDomain = Thread::GetDomain();
asmBuilder = currentDomain->DefineDynamicAssembly(asmName,AssemblyBuilderAccess::RunAndSave);
// Create a dynamic module.
modBuilder = asmBuilder->DefineDynamicModule(name);
}
public:
// Constructor.
CodeEmitter(String ^ AssemblyName){
prepareAssembly(AssemblyName);
}
// Create a new type.
TypeBuilder^ CreateType(String^ name){
// Check the input.
if(!name){
throw gcnew ArgumentNullException("AssemblyName");
}
return modBuilder->DefineType( name );
}
// Write the assembly.
void WriteAssembly(MethodBuilder^ entryPoint){
// Check the input.
if(!entryPoint){
throw gcnew ArgumentNullException("entryPoint");
}
asmBuilder->SetEntryPoint( entryPoint );
asmBuilder->Save( asmName );
}
};
void main()
{
// Create a CodeEmitter to handle assembly creation.
CodeEmitter ^ e = gcnew CodeEmitter("program.exe");
// Create a new type.
TypeBuilder^ mainClass = e->CreateType("MainClass");
// Create a new method.
MethodBuilder^ mBuilder = mainClass->DefineMethod("mainMethod", MethodAttributes::Static);
// Create an ILGenerator and emit IL for
// a simple "Hello World." program.
ILGenerator^ ilGen = mBuilder->GetILGenerator();
ilGen->Emit(OpCodes::Ldstr, "Hello World");
array<Type^>^mType = {String::typeid};
MethodInfo^ writeMI = Console::typeid->GetMethod( "WriteLine", mType );
ilGen->EmitCall(OpCodes::Call, writeMI, nullptr );
ilGen->Emit( OpCodes::Ret );
/////////////////////////////////////////////////
/////////////////////////////////////////////////
// Apply a required custom modifier
// to a field.
/////////////////////////////////////////////////
/////////////////////////////////////////////////
array<Type^>^fType = {IsLong::typeid};
mainClass->DefineField("modifiedInteger", Type::GetType("System.Int64"), fType, nullptr, FieldAttributes::Private);
// Create the type.
mainClass->CreateType();
// Write the assembly using a reference to
// the entry point.
e->WriteAssembly(mBuilder);
Console::WriteLine(L"Assembly created.");
}
Remarks
The C++ standard indicates that a long
value and an integer value are distinct types. However, they are both represented using ELEMENT_TYPE_I4
in an assembly. To distinguish a long
from an integer in C++, the Microsoft C++ compiler adds the IsLong modifier to any instance of a long
when the instance is emited. This process is critically important for maintaining language-level type safety.
Compilers emit custom modifiers within metadata to change the way that the just-in-time (JIT) compiler handles values when the default behavior is not appropriate. When the JIT compiler encounters a custom modifier, it handles the value in the way that the modifier specifies. Compilers can apply custom modifiers to methods, parameters, and return values. The JIT compiler must respond to required modifiers but can ignore optional modifiers.
You can emit custom modifiers into metadata using one of the following techniques:
Using methods in the TypeBuilder class such as DefineMethod, DefineField, DefineConstructor, and DefineProperty.
Generating a Microsoft intermediate language (MSIL) instruction file that contains calls to
modopt
andmodreq
, and assembling the file with the Ilasm.exe (IL Assembler).Using the unmanaged reflection API.