Question: Is it possible to set a name for anonymous unions using an annotation comment to the C/C++ source code?

I would like to know if is possible to suggest to bindgen a name for anonymous unions.

For example, if I have this structure:

typedef struct
{
	unsigned int	tCL;
	union {
	unsigned int	tRCD;
	unsigned int	tRCD_RD;
	};
	unsigned int	tRCD_WR,
			tRP,
			tRAS,
			tRC,

			tRCPB,
			tRPPB;
	union {
	unsigned int	tRRD;
	unsigned int	tRRDS;
	};
	unsigned int	tRRDL,
			tRRDDLR,

			tFAW,
			tFAWSLR,
			tFAWDLR,

			tWTRS,
			tWTRL,
			tWR;
} RAM_TIMING;

bindgen generates a rust struct like this:

#[repr(C)]
#[derive(Copy, Clone)]
pub struct RAM_TIMING {
    pub tCL: ::std::os::raw::c_uint,
    pub __bindgen_anon_1: RAM_TIMING__bindgen_ty_1,
    pub tRCD_WR: ::std::os::raw::c_uint,
    pub tRP: ::std::os::raw::c_uint,
    pub tRAS: ::std::os::raw::c_uint,
    pub tRC: ::std::os::raw::c_uint,
    pub tRCPB: ::std::os::raw::c_uint,
    pub tRPPB: ::std::os::raw::c_uint,
    pub __bindgen_anon_2: RAM_TIMING__bindgen_ty_2,
    pub tRRDL: ::std::os::raw::c_uint,
    pub tRRDDLR: ::std::os::raw::c_uint,
    pub tFAW: ::std::os::raw::c_uint,
    pub tFAWSLR: ::std::os::raw::c_uint,
    pub tFAWDLR: ::std::os::raw::c_uint,
    pub tWTRS: ::std::os::raw::c_uint,
    pub tWTRL: ::std::os::raw::c_uint,
    pub tWR: ::std::os::raw::c_uint
}

I was wondering if there is a way to specify a name for all the anonymous fiels, like __bindgen_anon_1 and RAM_TIMING__bindgen_ty_1.

I don't know if it makes sense, but I was hoping to be able to do something like:

typedef struct
{
	unsigned int	tCL;
        /// <div rustbindgen name="tRCD_u"></div>
	union {
	unsigned int	tRCD;
	unsigned int	tRCD_RD;
	};
[...]

to generate something like this:

#[repr(C)]
#[derive(Copy, Clone)]
pub struct RAM_TIMING {
    pub tCL: ::std::os::raw::c_uint,
    pub tRCD_u: RAM_TIMING__tRCD_u,
[...]

Unfortunately I cannot simply give a name to the union. If the comment solution is not possible, is there any other way to control the name used by the generated code in case of anonymous unions?

Start by reviewing bindgen's handling of anonymous unions and whether source comments are inspected for naming hints. Compare the requested C/C++ example with the generated Rust names, then determine whether the result should be implemented or documented as unsupported. Done means establishing a clear way to control both generated anonymous-union names, or clearly explaining why it is not possible.