http://d.puremagic.com/issues/show_bug.cgi?id=3762

           Summary: Restrictive functionality for template instance
                    recursive expansion
           Product: D
           Version: 2.039
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: curoles@yahoo.com
                CC: curoles@yahoo.com


--- Comment #0 from Igor Lesik <curoles@yahoo.com> 2010-01-31 14:30:04 PST ---
How to reproduce:
template static_factorial(int n)
{
    static if (n == 1)
        const static_factorial = 1;
    else
        const static_factorial = n * static_factorial!(n-1);
}

void main()
{
    writefln("502!=%d", static_factorial!(502));

Error: template instance factorial.static_factorial!(2) recursive expansion

Max recursion depth 500 is hardcoded in template.c function TemplateInstance::semantic() line 3738 if (++nest > 500). While 500 is reasonable practical limit, it would be nice to be able to control it somehow, with #pragma for example.

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--- Comment #1 from Don <clugdbug@yahoo.com.au> 2010-02-04 05:53:45 PST ---
> While 500 is reasonable practical limit, it would be nice to be able to
control it somehow, with #pragma for example.

Do you have ANY use cases for this? The limit is (a) to prevent the compiler from crashing with a stack fault; and (b) to warn the user when they have inadvertently created an infinite loop.

By the way, on DMD, the limit couldn't be set much higher. It blows the stack
at about 700. If there were a pragma, its only effect would be to create an
error message stating that the limit cannot be increased above 500.
I just don't believe that it is 'restrictive' in any meaningful sense.

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--- Comment #2 from Igor Lesik <curoles@yahoo.com> 2010-02-04 10:57:03 PST ---
No, I do not have any real use case for this. I have to admit that after all it is not that restrictive.

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Igor Lesik <curoles@yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


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