be set using the directives, not the environment variables, so that builds
work in unmodified environments.
-Within the Go file, C identifiers or field names that are keywords in Go
+Within the Go file, C's struct field names that are keywords in Go
can be accessed by prefixing them with an underscore: if x points at a C
struct with a field named "type", x._type accesses the field.
To access a struct, union, or enum type directly, prefix it with
struct_, union_, or enum_, as in C.struct_stat.
+As Go doesn't have support for C's union type in the general case,
+C's union types are represented as a Go byte array with the same length.
+
Go structs cannot embed fields with C types.
Any C function (even void functions) may be called in a multiple