Cryptic DMD error

Lars T. Kyllingstad public at kyllingen.NOSPAMnet
Fri May 8 06:14:34 PDT 2009


Don wrote:
> Lars T. Kyllingstad wrote:
>> Can someone with knowledge of the DMD source code please explain this 
>> error message for me?
>>
>> dmd: glue.c:652: virtual void FuncDeclaration::toObjFile(int): 
>> Assertion `!v->csym' failed.
>>
>> I had a look at the DMD source to try and make some sense of it 
>> myself, but didn't succeed. I am using the latest DMD, 2.029.
>>
>> I am in the middle of porting a library from D1 to D2, and as there is 
>> no mention of a file name, let alone a line number, I find it hard to 
>> narrow down the cause of the error.
>>
>> Thanks,
>>
>> -Lars
> Compile with -v, and you'll find the file DMD was working on when it 
> crashed. Please enter a test case into Bugzilla.


Thank you! Thanks to this little piece of advice, I've managed to narrow 
  it down enormously, and also to work around it. I'm having problems 
reproducing it as a simple test case, though.

Using the -v switch, the last thing DMD says before bailing out is 
"function  qagiIntegrateUpper". So here's a snippet from the troublesome 
code:

---
Result!(Real) qagiIntegrateUpper(Real, Func)
   (Func f, Real a, Real epsAbs, Real epsRel, Workspace!(Real) workspace)
{
     mixin AssertRealType!("qagiIntegrate", Real);
     mixin AssertSignature!("qagiIntegrate", Func, Real, Real);

     // Map onto the interval (0, 1).
     auto trans = transform!(Func, "f(a + (1-t)/t)/(t*t)", a)(f);

     return qagsIntegrate(trans, cast(Real)0.0, cast(Real)1.0,
         epsAbs, epsRel, workspace, Rule.GK15);
}
---

The line that starts with "auto trans ..." is the one that causes 
problems. The function transform!(...)(f) does what you think it does; 
it takes the function f and transforms it according to the string 
template parameter. The result is a struct with an opCall method and a 
field containing a copy of the template parameter a (which is passed to 
the template by alias).

I've been able to work around the error by replacing this line with the 
following:

---
Real b = a;
auto trans = transform!(Func, "f(b + (1-t)/t)/(t*t)", b)(f);
---

Thus, what is passed on to transform() is a locally declared variable, 
and not an argument to the function qagiIntegrateUpper(). Why this 
should matter, I have no idea.

But, as already mentioned, I have so far not been able to create a 
simple test case for reproducing the bug, and I'm pretty sure nobody 
wants the entire code for transform() in Bugzilla...

I'll continue working on it, though.

-Lars


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