libpq: how to get error code (not message)

Hello,

I'm writing a client in C++ using the C-library
(libpq) interface to PostgreSQL server.

I would like to know what function to call to obtain
one of the codes listed at 

http://www.postgresql.org/docs/7.4/static/errcodes-appendix.html

(I'm aware from other postings that in JDBC it would
be a getSQLState() call, but what if I have to code
the client in C/C++ and use libpq ?)

I found that the error codes are defined in file
errcodes.h under the /server include directory, but
can't find the client-side function that returns them.

Any hints are much appreciated,
Serge


    
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