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

[ludo@gnu.org (Ludovic Courtès)]

Mark H Weaver <mhw@netris.org> skribis:

> 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.

The difficulty is that ISO-8859-1 is not available during bootstrap, due
to guile-default-utf8.patch.

Commit dd0a8ef asks for ISO-8859-1 in the patch-* procedures, as you
suggest, but in reality during bootstrap what happens is not exactly
that.

If the bootstrap glibc had statically-linked gconv modules, we could get
rid of guile-default-utf8.patch.

> A better solution going forward would be to implement and use a
> permissive UTF-8 encoding in Guile.

Probably, although it’s not completely clear to me how that would work.
I suppose the idea would be to change to ISO-8859-1 when an invalid byte
sequence is encountered?

Ludo’.