Experimental Physics and
Industrial Control System

Bob Soliday <[email protected]> · Tue, 21 Apr 2009 15:29:06 -0500

Bob Soliday wrote:

Schoeneburg, Bernd wrote:

Hi all,

when I try to initalize a long variable with the most negative value

of -2147483648 which should be 0xFFFFFFFF, then I get a compiler

warning. The compiler is gcc version 3.4.5 running on solaris.

long test_var = -2147483648L;
....

../devPbdp.c:80: warning: decimal constant is so large that it is

unsigned

-2147483647 is accepted. This problem exists only with long. char and

short can be initialized to the most negative values without any problem.

Any idea? Thank you....

- Bernd

> /usr/include/sys/types.h defines LONG_MIN as -2147483647L-1L
>
> I don't know why they defined it this way but I assume there
> is a reason.
>
> --Bob
>

I have figured out the reason this works. The language syntax definition

doesn't define negative number literals, rather the negative numbers are

generated by the unary - operator. What this means is that it is not

reading -2147483648L the way you think it is. Instead it is reading it

as -(2147483648L). Since 2147483647L is equal to LONG_MAX it does not

know what to do with a number even bigger.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System