Why is align() on structures not allowed within unit-test code blocks?

[Timon Gehr]

On 12/04/2011 03:01 PM, GrahamC wrote:
> Is there a good reason why align() applied to structure definitions is not allowed on the struct definition line within unit-test code blocks?
>
> E.g.:
>
> unittest {
>
>       align(1) struct Foo {
>          char	c;
>   	      int		i;
>      }
>
>       void Bar() {
>   	        Foo f;
>       }
>
> }
>
> int main() {
>       return 0;
> }
>
>
> fails to compile. The error message is:
>      found 'align' instead of statement
>
> The error message is the same for both DMD and GDC.
>
> If you take the align(1) out it compiles OK.
> If you move the structure definition out of the unit-test block but leave the align(1) in place it compiles OK.
> If you put the align(1) on each member variable definition instead of the struct line it compiles OK.
>
> If the structure type is only used within the unit-test code then I would think it ought to be possible to define it (including it's alignment attribute) within that unit-test code block.

The reason is that it is parsed as function-local and that DMD's parser 
for some strange reason uses different grammar rules for declarations 
when inside a function body. You could maybe file a bug report.

A possible workaround is to take the declaration out of the unittest 
block and wrap it into a version(unittest) block like this:


version(unittest) {
     align(1) struct Foo {
         char c;
         int i;
     }
}
unittest {
     void Bar() {
         Foo f;
     }
}

int main() {
      return 0;
}

It invades the namespace of the module when compiling with -unittest though.