Using //export in a file places a restriction on the preamble:
since it is copied into two different C output files, it must not
contain any definitions, only declarations. If a file contains both
definitions and declarations, then the two output files will produce
duplicate symbols and the linker will fail. To avoid this, definitions
must be placed in preambles in other files, or in C source files.

which the .s files can then <code>#include</code>.
The file contains symbolic <code>#define</code> constants for the
offsets of Go struct fields, the sizes of Go struct types, and most
Go <code>const</code> declarations defined in the current package.
Go assembly should avoid making assumptions about the layout of Go
types and instead use these constants.
This improves the readability of assembly code, and keeps it robust to

type comparable interface{ comparable }

// iota is a predeclared identifier representing the untyped integer ordinal
// number of the current const specification in a (usually parenthesized)
// const declaration. It is zero-indexed.
const iota = 0 // Untyped int.

// nil is a predeclared identifier representing the zero value for a
// pointer, channel, func, interface, map, or slice type.