Re: Re: [SQL] g++ not working for postgresql extension languages? - Mailing list pgsql-interfaces

Hello All,

I have gotten the EXTERN "C" statement to work with the simple test c++
functions, but I cannot get it to work with the my actual crypto4.0 c++ sources
which I am able to compile all together into a single funcs.so file.

I am getting no errors but when I go into the "psql trdata" and try the same
test then I get this error:

[root@Treazurac /test]# psql trdata
Welcome to psql, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms      \h for help with SQL commands      \? for help on internal slash commands
    \g or terminate with semicolon to execute query      \q to quit
 

trdata=# select concat_text('a','d');
ERROR:  Load of file /test/trfuncs.so failed: /test/trfuncs.so: undefined
symbol: MemoryContextAlloc__FP17MemoryContextDataUi

-----------------------------------------------------------------------------

I do not know what is going on here because I did a simple test without my
cyrpto4.0 c++ files and using 3 different copies of concat_text(),
concat1_text() and concat2_text() which compiled and even ran fine.  

now when I put in my other sources which compile correctly outside of
Postgresql, I get the above error.

I have zipped up the test files and will send them to someone if you would like
to take a quick look. Just let me know as I am at a loss as to why PostgreSQL
is having som much trouble with this C++ interface.

Cheers
Lonnie

--- Stephen Jackson <Stephen.Jackson@panting-deer.org.uk> wrote:
> Lonnie,
>                  
> C++ uses "name mangling" to permit overloading of functions. Therefore
> your function concat_text() ends up with a very different name. You can
> probably get round this as follows:
> 
> #ifdef __cplusplus
> extern "C" {
> #endif
> text *
> concat_text(text *arg1, text *arg2);
> #ifdef __cplusplus
> }
> #endif
> 
> This tells the C++ compiler that concat_text is a "C" name - so don't do
> name mangling. This is a common technique for making C++ code callable
> from C, although I haven't used it in the specific context you are
> using.
> 
> Hope this helps,
> 
> Stephen Jackson
> Home: Stephen.Jackson@panting-deer.org.uk  www.panting-deer.org.uk
> Work: Stephen.Jackson@looksystems.co.uk    www.looksystems.co.uk
> 
> Lonnie Cumberland wrote:
> > 
> > Hi All again,
> > 
> > One more thing that I have tried.
> > 
> > If I now do a similar thing as in my previous message with the "funcs.c"
> file,
> > but this time with the "funcs.cc" file then I can get:
> > 
> 
> [snip]
> 
> > 
> > trdata=# select concat_text('a','b');
> > ERROR:  Can't find function concat_text in file /test/funcs.so
> > trdata=#
> > --------------------------------------------------------------------------
> > 
> 
> [snip]
> 
> > 
> > text *
> > concat_text(text *arg1, text *arg2);
> > 
> 
> [snip]
> 
> > so now I do not understand why the "gcc" version works and the "g++"
> version
> > does not?
> > 
> > Just a side note in that I can easliy compile c++ the examples in the
> > interfaces/libpq++ directory without any problems so that this is very
> strange
> > to me.
> > 
> > I really need the "g++" version to work correctly as well?
> > 
> > Any ideas anyone?
> > 
> > Cheers
> > Lonnie
> >
> 
> ---------------------------(end of broadcast)---------------------------
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