Re: gcc-3.2.1_gpc-20021128 16#80000000

Martin G C Davies wrote:

Now I have bumped into a difference (I have an easy workaround for me real code but I thought people might be interested).

Build and run the program below.

program mgcd_program;

var num : integer ;

begin num := -2147483648 ;

if num = 16#80000000 then

writeln( 'equal' ) else writeln( 'not equal' ) end.

When I build with

gpc version 2.1 (20020510), based on gcc-2.8.1

I get the output "equal".

When I build with

gpc version 20021128, based on gcc-3.2.1

I get the output "not equal".

The C program:-

main() { int num = -2147483647 - 1 ;

if ( num == 0x80000000 )

printf( "equal\n" ) ; else printf( "not equal\n" ) ; }

always returns "equal".

Anyway, clearly there is an inconsistency between the GPC versions.

Indeed, but since in Pascal "not equal" is correct, I'm glad it's so. I suppose it's the result of the following bug fix:

@item 20020904: comparisons between signed and unsigned integers sometimes give wrong results (eike2.pas, fjf664.pas)

According to C semantics, I guess "equal" is correct (since it silently ignores overflows, AFAIK). (At least on 32 bit systems. If int is 64 bits, it would probably be "not equal", too.)

Frank