Re: Alternatives to variable length arrays in pvData c++?

[Benjamin F. <ben...@he...>]

Am Mittwoch, 7. September 2011, um 19:29:59 schrieb Marty Kraimer:
> On 09/07/2011 12:42 PM, jam...@di... wrote:
> > The obvious is std::vector<FieldConstPtr> fields(numberNewFields) if
> > you can take the hit of heap allocation. I don't have a nice feeling
> > about alloca.
>
> I think that You are marching down a path You will not like.
>
> Any windows expert have any ideas?

Not a windows expert at all, but I had the same problem in the sequencer.
After many iterations we arrived at this code:

// somewhere near top of file:

#ifdef _WIN32
#  include <malloc.h>
#elif (__STDC_VERSION__ < 199901L) && !defined(__GNUC__)
#  include <alloca.h>
#endif

...

// use site

epicsShareFunc pvStat caVariable::get( pvType type, unsigned count, pvValue
*value )
{
    int caType = typeToCA( type );
#if (__STDC_VERSION__ >= 199901L) || defined(__GNUC__)
    char caValue[dbr_size_n( caType, count )];
#else
    char *caValue = (char*)alloca( dbr_size_n( caType, count ) );
#endif
    ...
}

Not nice but, AFAIK, this version compiles and works on all architectures and
compilers that EPICS currently supports.

Cheers
Ben

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