Subject: Re: ECPG and C++ compilation
From: Matthew Vanecek <mevanecek@yahoo.com>
To: Michael Meskes <meskes@postgresql.org>
Cc: Postgresql Interfaces List <pgsql-interfaces@postgresql.org>
In-Reply-To: <20030224152458.GA2980@feivel.fam-meskes.de>
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	<1045926883.27169.76.camel@reliant.home.pri>
	<20030224152458.GA2980@feivel.fam-meskes.de>
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Date: 25 Feb 2003 14:44:45 -0600

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On Mon, 2003-02-24 at 09:24, Michael Meskes wrote:
> On Sat, Feb 22, 2003 at 09:14:43AM -0600, Matthew Vanecek wrote:
> > I don't think that will work.  I can never get ecpg to recognize
> > typedefed structs, even when declaring the typedefed struct within a
> > DECLARE SECTION.
>=20
> Now that I do not understand. What exactly doesn't work? do you have a
> small example?
>=20

#include <stdio.h>

EXEC SQL BEGIN DECLARE SECTION;
struct s_somestruct {
    int id;
    char *field;
};

typedef struct s_somestruct SomeStruct;
EXEC SQL END DECLARE SECTION;

int main(int argc, char **argv)
{
    printf("this is just to show parse errors from ecpg\n");
    return 0;
}

yields:

me2v@reliant conn $ ecpg example.pgc=20
example.pgc:7: ERROR: parse error at or near ";"

If instead I use:

 #include <stdio.h>

struct s_somestruct {
    int id;
    char *field;
};

EXEC SQL BEGIN DECLARE SECTION;
typedef struct s_somestruct SomeStruct;
EXEC SQL END DECLARE SECTION;

int main(int argc, char **argv)
{
    printf("this is just to show parse errors from ecpg\n");
    return 0;
}

I get:
me2v@reliant conn $ ecpg example.pgc=20
example.pgc:9: ERROR: parse error at or near "SomeStruct"

I get this error also if I use:

EXEC SQL BEGIN DECLARE SECTION;
struct s_somestruct {
    int id;
    char *field;
} a_struct;

typedef struct s_somestruct SomeStruct;
EXEC SQL END DECLARE SECTION;

Doing "typedef struct { /* stuff */ } AStruct;" appears to work with
ecpg from 7.3.2, but IIRC, it would not work in 7.2.3.

> > Probably doing the sizeof calculation within ecpg would be the proper
> > way to go, and using that value in the ECPGdo call instead of
> > sizeof(whatever).  With respect to C++, anyhow.  I'm sure the developers
>=20
> But that would mean you cannot precompile on one machine for usage on
> another. Right?
>=20

Is sizeof() a compile-time execution/calculation?  If so, then it would
definitely not be portable, unless you implemented/used a generic types
library (such as glib, for example).  Since it works in C, though, and
ECPG generates C, I'm by no means making a suggestion to follow this
path. ;)


--=20
Matthew Vanecek
perl -e 'print $i=3Dpack(c5,(41*2),sqrt(7056),(unpack(c,H)-2),oct(115),10);'
***************************************************************************=
*****
For 93 million miles, there is nothing between the sun and my shadow except=
 me.
I'm always getting in the way of something...

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