IL_0017: callvirt instance void Sample.M圜lass::DoSome() IL_000c: callvirt instance void Sample.M圜lass::DoSome() IL_0000: newobj instance void Sample.M圜lass.ctor()
Downcasting object referencesĬ# provides two ways for casting object references (note that all types, unless those studied in the previous section, are reference types): Note that the last type cast doesn't need an explicit " Conv" opcode due to the nature of the involved types: int and uint these types have a very close storage structure (big endian bit order with a sign bit in the signed type) and conversion sign issues must be controlled by the programmer.Ī special kind of primitive type is bool (handled internally as an int), whose conversions to numeric types (and backward) are not allowed in C#, so we will not study them. The same conversions are applied in 64-bit data types, such as double, long and ulong. From now, we know that the "innocent" explicit and implicit conversions between primitive types generate instructions which can be avoided with a consistent type usage. Let's see a simple example about using and casting primitive types:Īs we can see, there are several Conv.XY instructions in the code, whose function is to convert the value at the top of the stack to the type designed in the opcode (r4, i4, etc.). Those types doesn't have inner structure, and are always passed by value if the programmer doesn't specify explicitly other behavior (using the out and ref modifiers). Primitive types are those non-composed types which can be handled directly by the (virtual) machine instructions, i.e., int, long, float, etc. We are going to study the MSIL generated code, but not the machine-specific instruction sequences due to the implementation and vendor dependency. This article analyzes the most common type casting situations and the compiler behavior in them. This can be a good approach in many cases, but managed languages are becoming more and more popular also for high-performance applications where the knowledge of the language, compiler, and runtime environment can enhance a program's quality and speed.
Swift downcast vs cast code#
Most C, C++, or Pascal programmers care about efficiency and speed of their code but those who use managed programming environments, such as Java, Visual Basic, or C# rely all the optimizing tasks on the compiler and the runtime environment. Explicit and implicit type casting is a common programming topic for almost any imperative programming language.
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