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Re: [Qemu-devel] [PATCH] trace: Fix 'char **' compilation error in simpl
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH] trace: Fix 'char **' compilation error in simple backend |
Date: |
Tue, 25 Oct 2016 21:56:43 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 10/25/2016 09:46 PM, Fam Zheng wrote:
> On Tue, 10/25 21:29, Eric Blake wrote:
>> On 10/25/2016 08:59 PM, Fam Zheng wrote:
>>> Currently, the generated function body will do "strlen(arg)" but the
>>> argument could be 'char **'. Avoid that by exclusding such cases in
>>
>>> def is_string(arg):
>>> strtype = ('const char*', 'char*', 'const char *', 'char *')
>>> - if arg.lstrip().startswith(strtype):
>>> + non_strtype = ('const char**', 'char**', 'const char **', 'char **')
>>> + arg_strip = arg.lstrip()
>>> + if arg_strip.startswith(strtype) and not
>>> arg_strip.startswith(non_strtype):
>>
>> There may be a more compact way to write it, but I'm not enough of a
>> python expert to know offhand what else to suggest (it's not as simple
>> as string concatenation of strtype + '*', since strtype is a tuple
>> rather than a string).
>
> Did you mean
>
> non_strtype = tuple(x + '*' for x in strtype)
Hmm, I guess that would work.
Or, what about a different approach, something like:
if arg_strip.startswith(strtype) and no_multiple_star(arg_strip):
for some sane definition of no_multiple_star() that checks that there is
exactly one '*' in a string. In C, I'd check roughly:
p = strchr(str, '*');
if (p && !strchr(p + 1, '*')) {
// treat str as string
}
but again, I'm not enough of an expert to pop that out late at night,
even if python has an easy one-liner way to express that.
> But personally I'd stick to the flatten version in this specific case for
> a bit more readability.
Indeed, and that's why I gave R-b as-is, even if it fails when there are
multiple 'const' qualifiers in a string with multiple '*' :)
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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