Re: 01/02: utils: Change 'patch-shebangs' to use binary input.

[Mark H Weaver <mhw@netris.org>]

Ludovic Courtès <ludo@gnu.org> writes:

> commit ca1e3ad2faa59d5b32289f84e0937fa476e21a1a
> Author: Ludovic Courtès <ludo@gnu.org>
> Date:   Sat Feb 28 01:01:51 2015 +0100
>
>     utils: Change 'patch-shebangs' to use binary input.
>     
>     * guix/build/utils.scm (get-char*): New procedure.
>       (patch-shebang): Use it instead of 'read-char'.
>       (fold-port-matches): Remove local 'get-char' and use 'get-char*'
>       instead.
> ---
>  guix/build/utils.scm |   22 +++++++++++-----------
>  1 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/guix/build/utils.scm b/guix/build/utils.scm
> index a3f8911..c98c4ca 100644
> --- a/guix/build/utils.scm
> +++ b/guix/build/utils.scm
> @@ -618,6 +618,14 @@ transferred and the continuation of the transfer as a thunk."
>           (stat:atimensec stat)
>           (stat:mtimensec stat)))
>  
> +(define (get-char* p)
> +  ;; We call it `get-char', but that's really a binary version
> +  ;; thereof.  (The real `get-char' cannot be used here because our
> +  ;; bootstrap Guile is hacked to always use UTF-8.)
> +  (match (get-u8 p)
> +    ((? integer? x) (integer->char x))
> +    (x x)))
> +

This is equivalent to reading with the ISO-8859-1 encoding.  The problem
is that the procedures that use 'get-char*' will then typically use
UTF-8 to write these characters back, so all non-ASCII characters will
get corrupted by these filters.

For now, I would suggest just using ISO-8859-1 for all of these build
utilities that filter or substitute existing files, and then use the
textual I/O procedures.  A better solution going forward would be to
implement and use a permissive UTF-8 encoding in Guile.

What do you think?

      Mark