Re: Possibly incorrect parsing of double doublequotes

[Mårten Wikström]

2011/5/11 Chet Ramey <chet.ramey@case.edu>:
> On 5/9/11 8:06 PM, Mårten Wikström wrote:
>
>> There are two problems/solutions here. The comment in the code above
>> seems to indicate that the quotes should actually be thrown away as is
>> done in 4.1. But on the other hand, word_list_remove_quoted_nulls()
>> seems to indicate it should remove all nulls, not just the first.
>> If I fix word_list_remove_quoted_nulls() to actually remove all
>> consecutive nulls, the problem is
>> solved. (At least my simple test-case works). If I revert the line
>> above to the 4.1 version it also
>> solves my problem.
>
> Unfortunately, that will not work.  You can't throw away the empty strings
> unless you're sure that you won't be performing word splitting.  The best
> example is
>
> f=" val" e=
> echo "$e"$f
>
> which should result in two fields, the first of which is the empty string.
> Bash-4.1 got that wrong.

Oh, I see. Thanks for pointing it out and for the illuminating example.

>>
>> Alas, my understanding of the bash code is fairly limited so my fixes
>> will likely break something. Perhaps someone with a little more
>> insight could tell the right(tm) solution.
>>
>> Anyway, here are the patches.
>> Solution 1, fixing remove_quoted_nulls():
>>
>> *** subst.c   2011-05-10 01:48:54.816322136 +0200
>> --- ../bash-4.2-patched/subst.c       2011-05-10 01:53:31.350806960 +0200
>> *************** remove_quoted_nulls (string)
>> *** 3706,3712 ****
>>           break;
>>       }
>>         else if (string[i] == CTLNUL)
>> !     i++;
>>
>>         prev_i = i;
>>         ADVANCE_CHAR (string, slen, i);
>> --- 3706,3713 ----
>>           break;
>>       }
>>         else if (string[i] == CTLNUL)
>> !         while (string[i] == CTLNUL)
>> !           i++;
>>
>>         prev_i = i;
>>         ADVANCE_CHAR (string, slen, i);
>
> It's the right place, but the wrong fix.  The code as it reads in bash-4.2
> skips over each character immediately following a CTLNUL.  If a sequence
> of CTLNULs appear, it skips every other one.  I attached a patch that does
> the right thing.

Ah, you are absolutely right. Thank you for the correction and the patch.

Regards,

Mårten