OS: Gentoo Linux with Kernel 2.6

D Compiler: dmd version 0.113

CODE:
# const int a1 = 50;
# const int a2 = 50;
# const int a3 = a1 * a2;
#
# const int b1 = a1 - 1;
# const int b2 = a2 - 1;
#
# const int c1 = 50*50;
# const int c2 = (a1-1)*(a2-1);
# const int c3 = b1*b2;
#
# int[4*c1]  array1;  // illegal!
# int[4*c2]  array2;  // illegal!
# int[4*c3]  array3;  // illegal!
#
# int[a3]    array4;  // valid! no error!
#
# void main()
# {
# }

OUTPUT:
test4(8):50*50 is not an expression
test4(9):a1 - 1 * a2 - 1 is not an expression
Segmentation fault

PROBLEM:

The compiler balks on calculated constant expressions. In arrays 1-3, take out the "4*" in the array dimension to get a different set of errors (no segfault).  Comment out the individual array declarations to get more complaints from the compiler.  Furthermore, remove all array declarations to get /no/ complaints from the compiler. The compiler error only shows up when you attempt to use the constants.

Since const values are the only replacement solution for the C preprocessor "#define", why are these expressions incalculable?

Win32 version not tested!

- John R.

John Reimer wrote:
> Win32 version not tested!
> 
> - John R.

dmd win32 fails too.

In article <pan.2005.02.20.14.41.58.234018@yahoo.com>, John Reimer says...
>
>OS: Gentoo Linux with Kernel 2.6
>
>D Compiler: dmd version 0.113
>
>CODE:
># const int a1 = 50;
># const int a2 = 50;
># const int a3 = a1 * a2;
>#
># const int b1 = a1 - 1;
># const int b2 = a2 - 1;
>#
># const int c1 = 50*50;
># const int c2 = (a1-1)*(a2-1);
># const int c3 = b1*b2;
>#
># int[4*c1]  array1;  // illegal!
># int[4*c2]  array2;  // illegal!
># int[4*c3]  array3;  // illegal!
>#
># int[a3]    array4;  // valid! no error!
>#
># void main()
># {
># }
>
>OUTPUT:
>test4(8):50*50 is not an expression
>test4(9):a1 - 1 * a2 - 1 is not an expression
>Segmentation fault
>
>PROBLEM:
>
>The compiler balks on calculated constant expressions. In arrays 1-3, take out the "4*" in the array dimension to get a different set of errors (no segfault).  Comment out the individual array declarations to get more complaints from the compiler.  Furthermore, remove all array declarations to get /no/ complaints from the compiler. The compiler error only shows up when you attempt to use the constants.
>
>Since const values are the only replacement solution for the C preprocessor "#define", why are these expressions incalculable?
>
>Win32 version not tested!
>
>- John R.

consts are sometimes astonishingly weak in D. I bet it would be fine if you used enum instead

- Kris

Kris wrote:

> consts are sometimes astonishingly weak in D. I bet it would be fine if you used
> enum instead
> 
> - Kris
> 
> 

Thanks, Kris.  If there's so much trouble with const's, I think this should be fixed.  I'll see what enum can do for me.  I guess a template could even be a solution, if not overkill.

- John R.

John Reimer wrote:
> Kris wrote:
> 
>> consts are sometimes astonishingly weak in D. I bet it would be fine if you used
>> enum instead
>>
>> - Kris
>>
>>
> 
> Thanks, Kris.  If there's so much trouble with const's, I think this should be fixed.  

No question about it :)

Frankly, I'd prefer Walter to remove const completely until he's spent some time thinking about how to correctly implement read-only variables, and the related ROM-based reference data. I doubt that will happen though.

- Kris

John Reimer wrote:
| OS:
| Gentoo Linux with Kernel 2.6
|
| D Compiler:
| dmd version 0.113
|
| CODE:
| # const int a1 = 50;
| # const int a2 = 50;
| # const int a3 = a1 * a2;
| #
| # const int b1 = a1 - 1;
| # const int b2 = a2 - 1;
| #
| # const int c1 = 50*50;
| # const int c2 = (a1-1)*(a2-1);
| # const int c3 = b1*b2;
| #
| # int[4*c1]  array1;  // illegal!
| # int[4*c2]  array2;  // illegal!
| # int[4*c3]  array3;  // illegal!
| #
| # int[a3]    array4;  // valid! no error!
| #
| # void main()
| # {
| # }
|
| OUTPUT:
| test4(8):50*50 is not an expression
| test4(9):a1 - 1 * a2 - 1 is not an expression
| Segmentation fault

Added to DStress as
http://dstress.kuehne.cn/run/const_14.d

Thomas