Re: [Qemu-devel] [RFC PATCH] vl.c: add -semihosting-config "arg" sub-argument

[Peter Maydell]

On 21 April 2015 at 17:48, Eric Blake <address@hidden> wrote:
> On 04/21/2015 09:55 AM, Peter Maydell wrote:
>> If you want pure POSIX shell then it is slightly
>> uglier as we have to invoke sed:
>>
>> argstr=""
>> for arg in "$@"; do
>>      o=$(printf '%s.\n' "$arg" | sed s/,/,,/g)
>>      argstr=${argstr:+$argstr,}arg=${o%.}
>> done
>
> It's possible to use IFS= and case to avoid the need to fork, while
> still writing portable shell, but the solution then takes LOTS more
> lines of code, so I'm not even going to bother to try writing it here.
>
> However, one thing this does NOT handle is an argument that is a literal
> ','.  That is, if I pass 'a', ',' and 'b' as my arguments, this script
> results in $argstr being a,,,,b, which the qemu parser would read as a
> single argument of 'a,,b' rather than the three intended arguments.

Hmm? You get "arg=a,arg=,,,arg=b". Does the parser not read that
the way I would expect?

> In order to handle that, you'd need some sort of solution that requires
> an unambiguous separation between arguments.  For example,
>
> --semihosting-options opt=a,,,,b
> vs.
> --semihosting-options opt=a,opt=,,,opt=b

The latter is what the script works with (except 'arg' rather
than 'opt').

Incidentally if you have a better idea for achieving the
desired goal than this messing around with comma-escaping
I would really like to know. I don't like either of the
current two proposals very much :-(

-- PMM