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Architecture Sets

Cesium targets .NET virtual machine, the CLI, which is independent of the target computer architecture in its nature.

At the same time, there are a lot of samples of C code that are machine-dependent. Certain parts of the C standard are impossible to represent in the platform-independent manner.

To manage that, Cesium introduces a concept of the architecture sets. An architecture set describes CPU architecture sets that share a common set of memory layout features for a Cesium program. Cesium cannot guarantee that all features of the C standard are supported on every architecture set.

Architecture set influences the following features of compiled programs:

  • pointer size,
  • size of pointer-dependent memory areas (such as stack arrays and arrays embedded into structures),
  • target architecture of the produced .NET assembly (not implemented yet, see issue #353: Assembly target architecture support),
  • ability to compile certain C constructs.

Cesium aims to support the following architecture sets:

  • 32b (aka Bit32): the set of architectures where the pointers are 32-bit-wide. Supports the C standard completely.

    Example architectures of this architecture set are x86 and ARM32.

  • 64b (aka Bit64): the set of architectures where the pointers are 64-bit-wide. Supports the C standard completely.

    Example architectures of this architecture set are x86_64 and ARM64.

  • Dynamic architecture has no fixed pointer size, and will calculate it in the runtime when required.

    Not every C construct allows to use dynamically-calculated size (in particular, it's impossible for pointer-dependent arrays embedded into structures), so this architecture doesn't support all the C standard. It still should be practical for many applications.

    This architecture is machine-independent and results in producing of an Any CPU-targeting assembly.

  • Wide architecture uses the fixed pointer size of 64 bits on all computers. This allows it to cover all the features of the C standard, for the cost of some redundancy on 32-bit architectures, and slightly different method signatures for .NET interop.

    This architecture is machine-independent and results in producing of an Any CPU-targeting assembly.

Specifically for the wide architecture, the types VoidPtr, CPtr<T> and FuncPtr<TDelegate> were introduced. They correspond to 64-bit pointers universally, and the wide architecture uses it in place of normal pointer types everywhere in the API. For cross-compatibility with any architecture, these types are also used in the Cesium.Runtime library. See the type system documentation for more information.