However, with those changes, I get:

--8<---------------cut here---------------start------------->8---
ice-9/boot-9.scm:106:20: Syntax error:
bytestructures/body/base.scm:38:0: definition in expression context, where definitions are not allowed, in form (define make-bytestructure-descriptor (case-lambda ((size alignment unwrapper getter setter) (%make-bytestructure-descriptor size alignment unwrapper getter setter #f)) ((size alignment unwrapper getter setter meta) (%make-bytestructure-descriptor size alignment unwrapper getter setter meta))))
Backtrace:
In ice-9/boot-9.scm:
 157: 12 [catch #t #<catch-closure 8c9560> ...]
In unknown file:
   ?: 11 [apply-smob/1 #<catch-closure 8c9560>]
In ice-9/boot-9.scm:
  63: 10 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
 432: 9 [eval # #]
In ice-9/boot-9.scm:
2401: 8 [save-module-excursion #<procedure 8e7880 at ice-9/boot-9.scm:4045:3 ()>]
4050: 7 [#<procedure 8e7880 at ice-9/boot-9.scm:4045:3 ()>]
1724: 6 [%start-stack load-stack #<procedure 8fa7a0 at ice-9/boot-9.scm:4041:10 ()>]
1729: 5 [#<procedure 8fdc60 ()>]
In unknown file:
   ?: 4 [primitive-load "/gnu/store/jx9byzydknqixyv4dn19cxa5q7r6s6v9-guile-bytestructures-20160726.53127f6-guile-builder"]
In ice-9/eval.scm:
 387: 3 [eval # ()]
 432: 2 [eval # #]
In ice-9/boot-9.scm:
 768: 1 [for-each #<procedure ca5030 at ice-9/eval.scm:416:20 (a)> #]
In unknown file:
   ?: 0 [scm-error misc-error #f ...]

ERROR: In procedure scm-error:
ERROR: Failed to compile "bytestructures/r7/base.scm" to "/gnu/store/m0lqx4wli55dfj45nsjhlhlvgql1p974-guile-bytestructures-20160726.53127f6/share/guile/site/2.0/bytestructures/r7/base.go"!
--8<---------------cut here---------------end--------------->8---

Could you look into it and submit and updated patch?

TIA!

Ludo’.