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boundary="_000_IA1PR12MB6065A69389852A81F579EAB9CB3E2IA1PR12MB6065namp_" MIME-Version: 1.0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: IA1PR12MB6065.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 89cbd340-ff05-4d08-3034-08dd19c95ba5 X-MS-Exchange-CrossTenant-originalarrivaltime: 11 Dec 2024 09:51:17.2695 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: UwjivU1aJ28MF3tx2IAtySPWf7rgrHR3A8EP0uaLJJUK1sBw8b2Iz9NAdGoCnqkkMdbKTD5ZpB2JbO06Hy2AqA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB8008 Sender: owner-sc22wg5@open-std.org Precedence: bulk --_000_IA1PR12MB6065A69389852A81F579EAB9CB3E2IA1PR12MB6065namp_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable For MPI reasons, I looked at the literals used by various Fortran compilers= for Booleans. Obviously, Fortran doesn=92t specify these, and I have heard the signed bit= was used for Booleans on the VAX. Today, the only values I see are 0 and = 1 or -1, both of which are compatible with C, at least in one direction. What I wonder is whether any implementation ever checks to see if a LOGICAL= value is strictly .TRUE. or .FALSE., i.e., detects alternative values of .= TRUE.. I assume that, for efficiency, compilers generate code equivalent t= o C and only looks for .TRUE. via a non-zero check. I can write tests for this, but I can=92t be sure that compilers don=92t en= able this check with uncommon flags, etc., and my ability to read assembly = has atrophied in the past few years. Thanks, Jeff Fortran Compiler Flags .FALSE. .TRUE. GCC 0 1 IFX 0 -1 (0xFFFFFFFF) IFX -fpscomp logicals 0 1 NVHPC 0 -1 (0xFFFFFFFF) LLVM (flang-new) 0 -1 (0xFFFFFFFF) Cray 0 1 --_000_IA1PR12MB6065A69389852A81F579EAB9CB3E2IA1PR12MB6065namp_ Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable

For MPI reasons, I looked at the literals used by va= rious Fortran compilers for Booleans.

 

Obviously, Fortran doesn=92t specify these, and I ha= ve heard the signed bit was used for Booleans on the VAX.  Today, the = only values I see are 0 and 1 or -1, both of which are compatible with C, a= t least in one direction.

 

What I wonder is whether any implementation ever che= cks to see if a LOGICAL value is strictly .TRUE. or .FALSE., i.e., detects = alternative values of .TRUE..  I assume that, for efficiency, compiler= s generate code equivalent to C and only looks for .TRUE. via a non-zero check.

 

I can write tests for this, but I can=92t be sure th= at compilers don=92t enable this check with uncommon flags, etc., and my ab= ility to read assembly has atrophied in the past few years.

 

Thanks,

 

Jeff

 

 

Fortran Compiler

Flags

.FALSE.

.TRUE.

GCC

0

1

IFX

0

-1 (0xFFFFFFFF)

IFX

-fpscomp logicals

0

1

NVHPC

0

-1 (0xFFFFFFFF)

LLVM (flang-new)

0

-1 (0xFFFFFFFF)

Cray

0

1

 

 

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