Function xmlParserErrorV 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn xmlParserErrorV(
    ctx: *mut c_void,
    msg: *const c_char,
    ap: *mut VaListTag,
) -> c_int

Variadic receiver for the xmlParserError shim: formats msg with the caller’s varargs and emits "error: " + formatted text through the generic channel (upstream error.c xmlVFormatLegacyError).

x86_64-only: the va_list layout (VaListTag) is the SysV AMD64 __va_list_tag; other ABIs carry their own varargs representation and the register-shim entry (xmlParserError) is x86_64-gated with it.

Safety

• msg must be a valid NUL-terminated printf format string, ap a valid va_list matching the format, ctx may be NULL.