Re: [Boost-users] [serialization] char[] and double

From: Larry Smith (larry.i.smith_at_[hidden])
Date: 2006-11-25 12:39:12

Robert Ramey wrote:
>> #include <boost/archive/text_iarchive.hpp>
>> #include <boost/archive/text_oarchive.hpp>
>>
>> #include "cmdef.h"
>>
>> namespace boost {
>> namespace serialization {
>>
>> template<class Archive>
>> void serialize(Archive & ar, struct NODE_MGR & st,
>>  const unsigned int version)
>> {
>>   ar & st.ApplName;  // line 19 in err msg
>>   ar & st.CompName;  // line 20 in err msg
>> }
>>
>> }  // end namespace serialization */
>> }  // end of namespace boost */
>>
>> --------------------
>>
>> /* arch.cpp */
>>
>> #include <sstream>
>>
>> #include "arch.hpp"
>>
>> int main()
>> {
>>   const struct NODE_MGR nm; // this will fix errors in second case - see 
>> rationale
>>   std::ostringstream ofs;
>>   boost::archive::text_oarchive oa(ofs);
>>
>>   oa << nm;  // line 15 in err msg
>>
>>   return 0;
>> }
> 
> 
>> Compiling arch.cpp produces these errors:
>>
>>   arch.hpp:19: error: cannot bind packed field
>>     ‘st->NODE_MGR::ApplName’ to ‘char (&)[8]
>>
>>   arch.hpp:20: error: cannot bind packed field
>>     ‘st->NODE_MGR::CompName’ to ‘char (&)[8]
>>
> 
>> However, on the workstation side the structs MUST remain
>> 'packed'; otherwise thousands of source files will have to
>> be modified.
> 
>> Is there any way to make this work with boost archives,
>> or should I explore other options?
> 
> I don't see how this could be addressed from within the serialization
> library.  It looks like anthing that looks like
> 
> ostream os;
> os << nm;
> 
> is going to fail as well.  I suspect that your strategy is going to be
> foiled whether you use the serialization or some other method.
> 
> Robert Ramey 
> 
> 
> 
> 
> 
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> 
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Ok, I see how 'const struct NODE_MGR nm' fixes part of
the problem...

I don't understand why the lib should care about the
data alignment of the struct's (packed versus unpacked).
If I remove 'packed' from the struct's it builds & works OK;
with 'packed' it won't compile.

On the server side (the receiver) 'packed' won't be used,
but on the workstation side (the sender) 'packed' must be
used to keep from breaking 100+ existing workstation apps.

Thanks for the help.

Larry