Thread: BUG #18231: String conversion function is adding special characters in Postgres 15

The following bug has been logged on the website:

Bug reference:      18231
Logged by:          anvesh work
Email address:      work.anvesh@gmail.com
PostgreSQL version: 15.0
Operating system:   Windows 10
Description:

I have a function which was working fine in Postgres 10 but not in Postgres
15.

When I traced the program, I am facing issue with the VARDATA(arg2). 
The arg2 is 2nd argument used in the calling function from PGAdmin4.
After conversion it is returning text with special characters.
In Postgres 10, note that 4 characters are concatenated with special
characters, but other characters are working fine.
Following are the lines of code:
pgsql:
select functionname('arg1', 'arg2', 'arg3');

My Method in C program has
 text  *arg2 = PG_GETARG_TEXT_P(1);
 int output = PbValue (VARDATA(arg2));

Postgres.h file:
#define VARDATA(PTR)                        VARDATA_4B(PTR)
#define VARDATA_4B(PTR)        (((varattrib_4b *) (PTR))->va_4byte.va_data)


To resolve this, we have used memcpy for converting characters.
 memcpy(str, VARDATA(arg2), arg_size);

On 07/12/2023 11:16, PG Bug reporting form wrote:
> The following bug has been logged on the website:
> 
> Bug reference:      18231
> Logged by:          anvesh work
> Email address:      work.anvesh@gmail.com
> PostgreSQL version: 15.0
> Operating system:   Windows 10
> Description:
> 
> I have a function which was working fine in Postgres 10 but not in Postgres
> 15.
> 
> When I traced the program, I am facing issue with the VARDATA(arg2).
> The arg2 is 2nd argument used in the calling function from PGAdmin4.
> After conversion it is returning text with special characters.
> In Postgres 10, note that 4 characters are concatenated with special
> characters, but other characters are working fine.
> Following are the lines of code:
> pgsql:
> select functionname('arg1', 'arg2', 'arg3');
> 
> My Method in C program has
>   text  *arg2 = PG_GETARG_TEXT_P(1);
>   int output = PbValue (VARDATA(arg2));
> 
> Postgres.h file:
> #define VARDATA(PTR)                        VARDATA_4B(PTR)
> #define VARDATA_4B(PTR)        (((varattrib_4b *) (PTR))->va_4byte.va_data)
> 
> 
> To resolve this, we have used memcpy for converting characters.
>   memcpy(str, VARDATA(arg2), arg_size);

I bet the problem is in your C function, but there's not enough details 
here to say where exactly. I don't understand what you mean string 
conversion or special characters, for starters.

If provide a short self-contained 10-20 lines example that demonstrates 
the problem, and send it as a reply to this list, someone might be able 
to point out what the problem is.

-- 
Heikki Linnakangas
Neon (https://neon.tech)