On Thu, Aug 2, 2012 at 9:04 PM, Paul Moore <pmo...@redhat.com> wrote:
> On Thursday, August 02, 2012 06:36:49 PM tmpsan...@gmail.com wrote:
> > From: "Thiago Marcos P. Santos" <thiago.san...@intel.com>
> >
> > It is always nice to provide this alternative version of variadic
> functions
> > since there is no portable way of wrapping them.
>
> Hmm, this would have been nice last week when I asked for any API changes.
> It
> doesn't mean we can't add it, just that the bar is a little bit higher now.
>
> I understand the basic why, but can you provide a concrete example of an
> application which needs this functionality?
>
> I'm also not sure about the new function names, I would like to keep the
> API
> "namespaced" with the "seccomp_" prefix ... maybe tack a "_va" on the end
> instead?
>
>
I have a class called SeccompFilters. I want to keep the seccomp context
private and at the same time I want to let people add rules by using the
addRule() method. For that I would need something like the code bellow.
void SeccompFilters::addRule(uint32_t action, int syscall, unsigned int
arg_cnt, ...)
{
va_list args;
va_start(args, arg_cnt);
int rc = seccomp_rule_add_va(m_context, action, syscall, arg_cnt, args);
// error handling, failure is fatal
va_end(args);
}
I'm tempted to handle every error when adding filters as fatal. People
willing to do the same, no matter if it is C or C++, can use the _va
functions to create a wrapper. C99 supports variadic macro, which might
help C developers, but doesn't solve my case because it could only be used
inside the class.
#define seccomp_rule_add_or_crash(context, action, syscall, arg_cnt, ...) \
ASSERT(seccomp_rule_add(context, action, syscall, arg_cnt,
##__VA_ARGS__) >= 0);
If you are curious about for what purpose this code has being worked on:
https://bugs.webkit.org/show_bug.cgi?id=89875
And I'm totally fine on changing the name. My original inspiration was the
[v]printf() family, but I guess it works for libc because they don't care
about namespace.
Cheers,
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