Re: Integer parsing bug?

Steve Atkins wrote:
> Section 8.1 of the manual gives the range of an integer
> as -2147483648 to +2147483647.
>
>
> template1=# select '-2147483648'::int;
> int4
> -------------
> -2147483648
> (1 row)
>
> template1=# select -2147483648::int;
> ERROR: integer out of range
>
> Oops.
>
> template1=# select version();
> version
> -------------------------------------------------------------
> PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC 2.96
> (1 row)
>
> Completely vanilla build - no options other than --prefix to
> configure. Clean installation, this is immediately after an initdb.
>
> I see the same bug on Solaris, built with Forte C in 64 bit mode.

Yep, it definately looks weird:

test=> select '-2147483648'::int;
int4
-------------
-2147483648
(1 row)

test=> select -2147483648::int;
ERROR: integer out of range
test=> select -2147483647::int;
?column?
-------------
-2147483647
(1 row)

test=> select '-2147483649'::int;
ERROR: value "-2147483649" is out of range for type integer

The non-quoting works only for *47, and the quoting works for *48, but
both fail for *49.

I looked at libc's strtol(), and that works fine, as does our existing
parser checks. The error is coming from int84, a comparison function
called from the executor. Here is a test program:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
long long l = -2147483648;
int i = l;

if (i != l)
printf("not equal\n");
else
printf("equal\n");
return 0;
}

A compile generates the following warning:

tst1.c:6: warning: decimal constant is so large that it is unsigned

and reports "not equal".

I see in the freebsd machine/limits.h file:

* According to ANSI (section 2.2.4.2), the values below must be usable by
* #if preprocessing directives. Additionally, the expression must have the
* same type as would an expression that is an object of the corresponding
* type converted according to the integral promotions. The subtraction for
* INT_MIN, etc., is so the value is not unsigned; e.g., 0x80000000 is an
* unsigned int for 32-bit two's complement ANSI compilers (section 3.1.3.2).
* These numbers are for the default configuration of gcc. They work for
* some other compilers as well, but this should not be depended on.

#define INT_MAX 0x7fffffff /* max value for an int */
#define INT_MIN (-0x7fffffff - 1) /* min value for an int */

Basically, what is happening is that the special value -INT_MAX-1 is
being converted to an int value, and the compiler is casting it to an
unsigned. Seems this is a known C issue and I can't see a good fix for
it except perhaps check for INT_MIN int he int84 function, but I ran
some tests and that didn't work either.

--
Bruce Momjian | http://candle.pha.pa.us
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