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From: "newbie-02 at gmx dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/113455] ROUNDING: IEEE Standard: Missing decimal rounding
 mode 'nearest, ties away from zero' for decimalxxx datatypes.
Date: Tue, 06 Feb 2024 00:48:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113455

--- Comment #5 from newbie-02 <newbie-02 at gmx dot de> ---
> If you're doing arithmetic with constant operands, it might be folded at =
compile time; make sure you're using -frounding-math to avoid that.=20=20

hmmmmm... that issue is left. From your comment I was in hope the following
program would work:=20=20
````=20=20
// compile with 'gcc -std=3Dgnu99 -I/usr/local/include/dfp -frounding-math =
-o
round_constants_ties_away round_constants_ties_away.c -ldfp',=20

#define __STDC_WANT_DEC_FP__=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20
        // req. for decimal rounding mode,=20
#include <fenv.h>=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
        // req. for decimal rounding mode,=20
#include <stdio.h>=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
        // reg. e.g. printf and perror,=20

int main( int argc, char *argv[ ] ) {=20
        fe_dec_setround( 4 );=20
        printf( "fe_dec_rounding_mode : %d \n", fe_dec_getround() );=20
        volatile _Decimal64 x1DD =3D 8.0000000000000015DD;=20
        volatile _Decimal64 x2DD =3D 8.0000000000000025DD;=20

        printf( "Read in of 8.0000000000000015 produced : %.17DE \n", x1DD =
);=20
        printf( "Read in of 8.0000000000000025 produced : %.17DE \n", x2DD =
);=20
        printf( "In operation it works                  : %.17DE \n", x2DD +
5E-16DD );=20

        return( 0 );=20
}=20
````=20=20

It works, but doesn't round the constants as wanted:=20=20

````=20=20
=E2=94=94=E2=94=80$ ./round_constants_ties_away=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
fe_dec_rounding_mode : 4=20
Read in of 8.0000000000000015 produced : 8.00000000000000200E+00=20
Read in of 8.0000000000000025 produced : 8.00000000000000200E+00=20
In operation it works                  : 8.00000000000000300E+00=20
````=