Question 1

How to build libffi on Windows with Visual Studio?

Accepted Answer

Use the msvcc.sh wrapper script during configuration, as detailed in the README, with specific commands for 64-bit builds (e.g., CC='path/to/msvcc.sh -m64') and options for clang-cl.

Question 2

What's the difference between libffi and Python's ctypes?

Accepted Answer

libffi is the low-level library that ctypes and other FFI systems are built upon; ctypes provides Python-specific bindings with higher-level conveniences, while libffi is for implementing such systems in any language.

Question 3

How to pass structs by value with libffi?

Accepted Answer

Libffi handles struct passing according to platform ABIs, but you must manually define the struct layout using ffi_type structures; recent updates ensure correct behavior, but it requires careful setup.

Question 4

Does libffi support C++ or other languages directly?

Accepted Answer

No, it's primarily designed for C calling conventions; for C++, you need to handle name mangling and object-oriented features separately, though it can serve as a base for language-specific FFIs.

Question 5

What are the performance costs of using libffi?

Accepted Answer

There's overhead due to dynamic calling and argument marshaling, but it's optimized for correctness across platforms; for performance-critical code, direct compiled calls are faster, and libffi is best for flexible, runtime scenarios.

Question 6

How to create a closure to call back into my interpreter?

Accepted Answer

Use ffi_prep_closure to set up a callable pointer, linking it to a callback function and data, as mentioned in the closure support feature; ensure proper memory management and platform-specific considerations.

libffi

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