return value of a version-1 C function (Solved) - Mailing list pgsql-general

[This message refers to my previous post '[GENERAL] return value of a version-1
C function']

Ooops, I didn't read the docs very carefully! I solved the problem, by
declaring cod as a proper structure and then returning it with
PG_RETURN_BPCHAR_P(cod):

  BpChar *cod = (BpChar *)SPI_palloc(VARHDRSZ + 8);
  char c[9];
  ...
  /* c = generated code (8 chars) + '\0' */
  ...
  cod->vl_len = VARHDRSZ + 8;
  memmove(VARDATA(cod), c, 8);

  PG_RETURN_BPCHAR_P(cod);
}

Now I have three more questions!

1) SPI_connect() and SPI_finish() mark a new memory context; since I must
return cod I need to SPI_palloc() it in the upper Executor context. The
problem is: how can I free the SPI_palloc()'ed memory? I can't SPI_pfree() it
before PG_RETURN_BPCHAR_P(cod), conversely nothing after
PG_RETURN_BPCHAR_P(cod) would be executed. As stated in section 22.3 of the
PostgreSQL Programmer's Guide 'SPI has no ability to automatically free
allocations in the upper Executor context!', hence the question: how do I cope
with this situation?

2) If I use the VARSIZE(__PTR) macro (defined in postgres.h) to set the size of
cod, the compiler will complain about an invalid lvalue. This is not valid:

VARSIZE(cod) = VARHDRSZ + 8;

Can I safely use:

cod->vl_len = VARHDRSZ + 8;

or is this incorrect?

3) The following variable is an identifier (Name):

Name tablename = PG_GETARG_NAME(0);

If I want to retrieve the string contained in the union pointed to by
tablename I should use the macro NameStr(name) defined in c.h:

(void)strlcat(query, NameStr(fieldname), sizeof(query));

but again the compiler will complain with the error "request for member `data'
in something not a structure or union". Name is a pointer to NameData
union:

typedef union nameData
{
        char            data[NAMEDATALEN];
        int                     alignmentDummy;
} NameData;
typedef NameData *Name;

NameStr is defined as:

#define NameStr(name)   ((name).data)

but name is a pointer, so shouldn't NameStr be defined as:

#define NameStr(name)   ((name)->data)

? Is it correct to use: tablename->data?

I attached the C code of the function. I'm not a C/PostgreSQL guru, so ANY
suggestion is welcome. Thanks in advance for your help.

    Francesco Casadei