Thread: Bug #894: different result with the same parameterlist in function call

Kovacs Balazs (balazs.kovacs@jonapot.hu) reports a bug with a severity of 3
The lower the number the more severe it is.

Short Description
different result with the same parameterlist in function call

Long Description
I have written a simple function in C under pg (it uses regex lib):
#include <stdio.h>
 #include <string.h>
 #include <regex.h>
 #include <postgres.h>
 #include <fmgr.h>

 PG_FUNCTION_INFO_V1(crightevaledge);
 Datum crightevaledge(PG_FUNCTION_ARGS)
 {
 text *pattern = (text*)PG_GETARG_TEXT_P(0);
 text *sample = (text*)PG_GETARG_TEXT_P(1);
 char *char_pattern = (char*)VARDATA(pattern);
 char *char_sample = (char*)VARDATA(sample);
 regex_t compre_pattern;
 int32 retval;

 if (regcomp(&compre_pattern,char_pattern,0)!=0) PG_RETURN_INT32(2);
 if (regexec(&compre_pattern,char_sample,0,NULL,0)==0) retval=1;
 else retval=0;
 regfree(&compre_pattern);
 PG_RETURN_INT32(retval);
 }

I compile it:
gcc -fpic -c -I/usr/local/postgresql-7.2.1/src/include -I/usr/local/pgsql/include sample.c
gcc -shared -o sample.so sample.o

and create a function under pg:
create function crightevaledge(text,text) returns int4 as '/devel/pg/sample.so' language 'C';

I have created a simple table for test, like this (in an empty database (named test)):
create table test(descr text,
path text);

I put into it some records:
insert into test values('test1','test1.dat');
insert into test values('test2','test2.mpg');
insert into test values('test3','test3.pdf');

After, i executed the following query more than 1 times:
select descr,crightevaledge('.*mpg',path) from test;
The result was different on different executing:

test=# select descr,crightevaledge('.*mpg',path) from test;
 descr | crightevaledge
-------+----------------
 test1 |              0
 test2 |              0
 test3 |              0
(3 rows)

test=# select descr,crightevaledge('.*mpg',path) from test;
 descr | crightevaledge
-------+----------------
 test1 |              0
 test2 |              1
 test3 |              0
(3 rows)

test=# select descr,crightevaledge('.*mpg',path) from test;
 descr | crightevaledge
-------+----------------
 test1 |              0
 test2 |              0
 test3 |              0
(3 rows)

test=# select descr,crightevaledge('.*mpg',path) from test;
 descr | crightevaledge
-------+----------------
 test1 |              0
 test2 |              1
 test3 |              0
(3 rows)

I use postgres 7.2.1 version, and redhat 7.2 (with kernel 2.4.20).

Sample Code


No file was uploaded with this report

pgsql-bugs@postgresql.org writes:
>  text *pattern = (text*)PG_GETARG_TEXT_P(0);
>  text *sample = (text*)PG_GETARG_TEXT_P(1);
>  char *char_pattern = (char*)VARDATA(pattern);
>  char *char_sample = (char*)VARDATA(sample);

You can't convert text* to char* with just a cast.  The result won't
(usually) be null-terminated where it should be; so you end up with
strings that have garbage on the end.  Use textout() like all the
existing code does when it wants a null-terminated string.

            regards, tom lane