Re: Is this a gnat bug?

[Ludovic Brenta <ludovic.brenta@insalien.org>]

hebisch@math.uni.wroc.pl (Waldek Hebisch) writes:

> I am trying to convert a sequence of eight bytes to a fixed point
> number. For testing I put bytes in an array. I first collect bytes
> in a modular type and then assign the result to an integer (I have
> eight bytes in big endian order, but the actual number should be
> small). When number formed from 4 lower order bytes is out of
> range I get CONSTRAINT_ERROR but if only higher order bytes are
> non-zero I get just zero result. I would expect CONSTRAINT_ERROR 
> always when any of higher order bytes is non-zero. With both 
> gnat-3.14p and gnat from gcc-3.3 the program below prints huge
> number for 'pp' and 0.0 for 'price'. 

Compile with -gnato.  With GNAT, range checks are disabled by default
for performance.  Here is what I get with 3.15p:

$ gnatmake -O3 tstnum
gnatgcc -c -O3 tstnum.adb
gnatbind -x tstnum.ali
gnatlink tstnum.ali

$ ./tstnum
pp =  17868022686844715008
price =  0.00

$ gnatmake -s -gnato -O3 tstnum
gnatgcc -c -gnato -O3 tstnum.adb
gnatbind -x tstnum.ali
gnatlink tstnum.ali

$ ./tstnum
pp =  17868022686844715008

raised CONSTRAINT_ERROR : tstnum.adb:20 overflow check failed


HTH

-- 
Ludovic Brenta.