Where are the .NET IL bytes stored in an .NET executable and how does the executable convert them to x86 in runtime?

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In a .NET executable, the Intermediate Language (IL) code is not stored in a directly executable form like machine code. Instead, it is stored in a Common Intermediate Language (CIL) format, also known as Microsoft Intermediate Language (MSIL), within the assembly's metadata. The IL code is located in the .exe or .dll file produced during compilation.

When a .NET executable is run, the Common Language Runtime (CLR) is responsible for executing the code. The CLR uses a Just-In-Time (JIT) compiler to convert the IL code to machine code at runtime. The process of converting IL to machine code occurs in the following steps:

  1. Loading: The CLR loads the .NET executable into memory, including the assembly's metadata, IL code, and other resources.

  2. Verification: The CLR performs a verification step to ensure the safety and integrity of the IL code. It checks for type safety, security permissions, and other validation checks to prevent potential security vulnerabilities or runtime errors.

  3. JIT Compilation: When a method is called for the first time, the JIT compiler kicks in. It compiles the IL code of that method into native machine code specific to the underlying hardware architecture (e.g., x86, x64, ARM) and generates an optimized version of the code.

  4. Execution: The native machine code produced by the JIT compiler is executed directly by the processor.

The JIT compilation process is performed on-demand, meaning that only the IL code that is actually needed for execution is compiled. Methods that are not called or accessed during the execution of the program are not JIT compiled.

It's worth noting that the JIT compilation process provides several advantages, including platform independence (the same IL code can be executed on different architectures) and runtime optimizations based on the specific hardware and execution environment. Additionally, the CLR handles other aspects such as memory management, garbage collection, and exception handling, providing a managed execution environment for .NET applications.