What C type should I use for f64 in my C FFIs?

Question

When I return i32 data from my C FFI functions, I use the datatype int32_t and it works like a charm. What is the equivalent of Rust's f64 datatype in C?

Answer 1

Use libc::c_double.

Other direct mappings:

f32 | c_float   
f64 | c_double  
i8  | int8_t    
i16 | int16_t   
i32 | int32_t   
i64 | int64_t   
u8  | uint8_t
u16 | uint16_t  
u32 | uint32_t  
u64 | uint64_t