Writing PostgreSQL Functions in C++

Question

I have some problem writing postgres functions in C++ while following the guides for C: C-Language Functions. I found that most postgres functions are written in C instead C++, but I have to use a lib that is written in C++, so I chose C++. My question is, is there anything to notice when writing in C++? It's common to write makefiles using pgxs, so how should I write the makefile to make it work? Thanks.

One thing to think about is that you might have to mark your C++ function as extern "C". — Some programmer dude
– Some programmer dude, Commented Dec 14, 2011 at 7:54
@JoachimPileborg Alas, it's nowhere near that easy. palloc() complicates things, c++ exception handling doesn't play well with C without very defensive coding at all C/C++ interface points, and Pg's longjmp based error handling throws a major spanner into the works. — Craig Ringer
– Craig Ringer, Commented Dec 14, 2011 at 11:43
To paraphrase Linus: c++ was only created to attract idiots. — wildplasser
– wildplasser, Commented Dec 14, 2011 at 12:19

Craig Ringer · Accepted Answer · 2011-12-14 12:16:15Z

6

If you can avoid doing it, do so. PostgreSQL doesn't mix especially well with C++. It's possible, ~~as shown by PostGIS~~, but it's not overly fun.

If you can, write or generate a pure C wrapper to your C++ library and use that wrapper to interact with the library. That won't be practical if it's heavily template based (eg: boost) or uses other more advanced C++ features, but works well if it's just C-with-objects style code. SWIG can help generate wrappers for you.

If you'd prefer to avoid the wrapper approach or if your library is a bit too complex, too exception-reliant, etc for that then you should read this PostgreSQL manual entry.

Search the PostgreSQL mailing list for more discussion on this topic.

edited Dec 14, 2011 at 12:16

answered Dec 14, 2011 at 11:41

Craig Ringer

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