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

[Leon Alrae]

On 02/04/2015 10:14, Leon Alrae wrote:
> On 02/04/2015 09:29, Liviu Ionescu wrote:
>>
>>> On 02 Apr 2015, at 10:56, Leon Alrae <address@hidden> wrote:
>>>
>>> ... The UHI semihosting supports Argn syscall which returns single argument,
>>> and Argn is called multiple times to build argv (each argument can
>>> contain whitespaces).
>>
>> ok, I don't want to comment too much on UHI design, since I'm not familiar 
>> with; at first sight it seems an improvement, but at second sight, from the 
>> user perspective, with your implementation, it looks overkill; all shells I 
>> know accept a single command line string, possibly with quotes if substrings 
>> need to preserve the separator spaces, and internally the shells themselves 
>> split the string into substrings and pass them to the application as (argc, 
>> argv).
> 
> How would you pass arguments containing whitespaces via
> -semihosting-config cmdline without having to reinvent shell within QEMU?

I missed the fact that you already provided the implementation for this
below... sorry. But still, the main point of arg is to keep it simple
and avoid dealing with implementing shell within QEMU. It is also
flexible, thus if a user finds it annoying to set each arg separately he
can have a wrapper responsible for parsing the command line and
translating into QEMU command line options.

Leon

> 
>>
>> in my opinion, if UHI semihosting supports single argument Argn syscalls, 
>> then it is the responsibility of the debugger (qemu in our case) to parse 
>> the command line and to provide the individual substrings in the desired 
>> format, and not ask the user to do this task manually.
> 
> Couldn't the user have a wrapper around QEMU doing it for him?
> 
> Leon
> 
>>
>> the ARM semihosting case, being more primitive in this respect, requires to 
>> run the code to split the line inside the debugged application.
>>
>> as an example, the projects generated by my GNU ARM Eclipse templates use
>>
>> https://sourceforge.net/p/micro-os-plus/iii/ci/master/tree/packages/portable/newlib.pack/src/newlib/_syscalls.c
>>
>> which, at line 419, has an __initialize_args() function.
>>
>> this is simplistic, to meet the bare metal limitations, but seems functional.
>>
>> I guess something similar, but more elaborate, can be added to qemu for UHI 
>> semihosting.
>>
>>> I believe having just one flexible command line option in QEMU
>>> satisfying these two cases would be ideal. But if arg doesn't suit your
>>> needs then as Matthew already mentioned we probably should go for having
>>> cmdline and arg mutually exclusive.
>>
>> from the user point of view, I still do not see the advantages of multiple 
>> arg=, it is easier to use quotes in a complete command line, like in any 
>> shell; so my vote still goes to cmdline=.
>>
>>
>> regards,
>>
>> Liviu
>>
>