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Re: [paho-dev] Using C++ with the Paho C client library
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Specifically, some objections to using const (in C).
1) I can't pass a char** to a const char** or a const char * const *
without a cast. Adding casts requires changing programs, apart from
the principle of adding what seem unnecessary casts. See:
int f(const char * const * c)
{
c = 0;
c[1] = 0;
c[0][0] = 1;
}
int main(int argc, char** argv)
{
f(argv); /* cast needed - why? */
return 0;
}
2) For char** topic, do you want const char** or const char* const *?
Presumably the latter, which I think is verging on the hard to understand.
Ian
On 16/05/13 23:00, Ian Craggs wrote:
I agree about the timing. The question would be when to fit in the
work of:
1) which of the parameters, elements of structures, etc to apply the
change to. Could be >50 parameters and elements to review.
2) whether to apply the change to #defines as well. I seem to
remember starting with const definitions, running into problems again,
and hence deciding to go with old-fashioned #defines. This would seem
to be more a C++ concern, and can be fixed in a C++ header anyway.
3) testing the implications on all main platform combinations,
including back to gcc 3.8 and older MS C/C++ compilers, for effects
and backward compatilbility.
Ian
On 16/05/13 22:15, Roger Light wrote:
Hi,
(2) Observe proper const-ness for pointer parameters if there is no
intent
in updating the item, particularly "const char*" for "char*"
DLLExport int MQTTAsync_create(MQTTAsync* handle,
const char* serverURI, const char* clientId, ...
It occurs to me that if this change is going to be made (and I'd agree
with it) it ought to be done sooner rather than later because it
represents an API change. Once there's a proper release and it is
being packaged it's a lot more awkward to change.
Cheers,
Roger
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