std::ffi

Trait VaArgSafe

1.99.0 · Source

pub unsafe trait VaArgSafe { }

ⓘ This trait cannot be implemented outside core.

Expand description

Types that are valid to read using VaList::next_arg.

This trait is implemented for primitive types that have a variable argument application-binary interface (ABI) on the current platform. It is always implemented for:

Implementations for e.g. i32 or usize shouldn’t be relied upon directly, because they may not be available on all platforms.

§Safety

When C passes variable arguments, signed integers smaller than c_int are promoted to c_int, unsigned integers smaller than c_uint are promoted to c_uint, and c_float is promoted to c_double. Implementing this trait for types that are subject to this promotion rule is invalid.

This trait is only implemented for 128-bit integers when the platform defines the __int128 type.