Re: [PATCH] Introduce hardbool attribute for C

[Alexandre Oliva via Fortran]

On Apr  6, 2023, Bernhard Reutner-Fischer  wrote:

> 29 For C_BOOL, the internal representation of .TRUE._C_BOOL and
> .FALSE._C_BOOL shall be the same as those of
> 30 the C values (_Bool)1 and (_Bool)0 respectively.

I'm not changing any of the standard types, FWIW.  The proposed
extension enables alternate boolean types to be introduced, with
extra checking for hardening.

> I personally like your proposed 0 and ~0, that's probably pretty robust.

That is only a default.  Certain applications may benefit from other
values.  0xa5 and 0x5a seem to make a good combination too.

-- 
Alexandre Oliva, happy hackerhttps://FSFLA.org/blogs/lxo/
   Free Software Activist   GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about 

Re: [PATCH] Introduce hardbool attribute for C

[Thomas Koenig via Fortran]

Hi Alexandre,


On Apr  6, 2023, Bernhard Reutner-Fischer  wrote:


29 For C_BOOL, the internal representation of .TRUE._C_BOOL and
.FALSE._C_BOOL shall be the same as those of
30 the C values (_Bool)1 and (_Bool)0 respectively.


I'm not changing any of the standard types, FWIW.  The proposed
extension enables alternate boolean types to be introduced, with
extra checking for hardening.


I personally like your proposed 0 and ~0, that's probably pretty robust.


That is only a default.  Certain applications may benefit from other
values.  0xa5 and 0x5a seem to make a good combination too.

In gfortran, we depend on the representation of 0/1 for several things
(among them avoiding having separate library versions for logical
kind=1,2,4,8,16 for MASK).

So, such a type would be incompatible with vanilla LOGICAL variables
and with C interop logical variables.

If anybody should pass such a hardbool variable to Fortran, they
will get unpredictable results, and deserve to lose.  The opposite
effect of what would be intended :-)

Best regards

Thomas