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digitalmars.D - Internal Error

reply "Neil Vice" <psgdg swiftdsl.com.au> writes:
I've encountered the following error in DMD 2.012:

    Internal error: ..\ztc\cod1.c 1662

I would submit a bug report except that I can't seem to determine a simple 
case that produces the bug, so I guess I'm looking for some assistance in 
narrowing down the problem.

I have two structs, one representing a time-stamp and another representing a 
time-period. They both implement opSub. Nested within a method in a class 
within a class in a seperate package I have some code along the lines of:

    auto result = a - (b - c);

where a is a TimePeriod and b & c are TimeStamps.

If I replace this line with:

    auto _result = b - c;
    auto result = a - _result;

the Internal error goes away.

I have attempted to construct a simple case with two similar structs with 
opSub methods and a main() containing the problem expression, however I 
cannot reproduce the error.

Any suggestions on where to go from here?
Apr 02 2008
next sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"Neil Vice" wrote in message

 I've encountered the following error in DMD 2.012:

    Internal error: ..\ztc\cod1.c 1662

 I would submit a bug report except that I can't seem to determine a simple 
 case that produces the bug, so I guess I'm looking for some assistance in 
 narrowing down the problem.

 I have two structs, one representing a time-stamp and another representing 
 a time-period. They both implement opSub. Nested within a method in a 
 class within a class in a seperate package I have some code along the 
 lines of:

    auto result = a - (b - c);

 where a is a TimePeriod and b & c are TimeStamps.

 If I replace this line with:

    auto _result = b - c;
    auto result = a - _result;

 the Internal error goes away.

 I have attempted to construct a simple case with two similar structs with 
 opSub methods and a main() containing the problem expression, however I 
 cannot reproduce the error.

 Any suggestions on where to go from here?


Try to reproduce the error with a simple main function that does just the 
lines above.

If this still fails, then try removing pieces of your classes, making sure 
the error remains.  When you narrow that down, you might be able to see 
clearer what the minimal case is.

If this doesn't fail, then try moving around where you are making the auto 
result = a - (b - c) call, trying to simplify that code.

Good luck.

-Steve
Apr 02 2008
parent "Neil Vice" <psgdg swiftdsl.com.au> writes:
"Steven Schveighoffer" <schveiguy yahoo.com> wrote in message 
news:ft04i9$5in$1 digitalmars.com...

 "Neil Vice" wrote in message

 I've encountered the following error in DMD 2.012:

    Internal error: ..\ztc\cod1.c 1662

 I would submit a bug report except that I can't seem to determine a 
 simple case that produces the bug, so I guess I'm looking for some 
 assistance in narrowing down the problem.

 I have two structs, one representing a time-stamp and another 
 representing a time-period. They both implement opSub. Nested within a 
 method in a class within a class in a seperate package I have some code 
 along the lines of:

    auto result = a - (b - c);

 where a is a TimePeriod and b & c are TimeStamps.

 If I replace this line with:

    auto _result = b - c;
    auto result = a - _result;

 the Internal error goes away.

 I have attempted to construct a simple case with two similar structs with 
 opSub methods and a main() containing the problem expression, however I 
 cannot reproduce the error.

 Any suggestions on where to go from here?


 Try to reproduce the error with a simple main function that does just the 
 lines above.

 If this still fails, then try removing pieces of your classes, making sure 
 the error remains.  When you narrow that down, you might be able to see 
 clearer what the minimal case is.

 If this doesn't fail, then try moving around where you are making the auto 
 result = a - (b - c) call, trying to simplify that code.

 Good luck.

 -Steve


Well I had another crack at it and have come up with a simpler case.

The error only occurs when you attempt an operation (duplicated only for + 
and - so far) on operands for which that operation has not been defined. 
Furthermore it appears that one of the operands must be a const variable. 
I've also only encountered the error when the other operand was the result 
of another expression i.e. not a simple variable.

What's interesting also is the fact that replacing "auto result = a - (b - 
c);" with "auto tmp = b - c; auto result = a - tmp;" neither causes the 
internal error nor causes a compile error due to the fact that the operation 
"a - tmp" is undefined as far as I can tell.

I wonder what the compiler actually generates there...

http://d.puremagic.com/issues/show_bug.cgi?id=1969
Apr 02 2008
prev sibling parent reply Russell Lewis <webmaster villagersonline.com> writes:
Neil Vice wrote:

 I've encountered the following error in DMD 2.012:
 
     Internal error: ..\ztc\cod1.c 1662
 
 I would submit a bug report except that I can't seem to determine a simple 
 case that produces the bug, so I guess I'm looking for some assistance in 
 narrowing down the problem.
 
 I have two structs, one representing a time-stamp and another representing a 
 time-period. They both implement opSub. Nested within a method in a class 
 within a class in a seperate package I have some code along the lines of:
 
     auto result = a - (b - c);
 
 where a is a TimePeriod and b & c are TimeStamps.
 
 If I replace this line with:
 
     auto _result = b - c;
     auto result = a - _result;
 
 the Internal error goes away.
 
 I have attempted to construct a simple case with two similar structs with 
 opSub methods and a main() containing the problem expression, however I 
 cannot reproduce the error.
 
 Any suggestions on where to go from here? 


Generally, I do binary search on my code.  I comment out huge swaths of 
code that I think might be irrelevant, then recompile.  If the failure 
goes away, then I only comment out half of that section, and try again.

It's a painful, iterative process, but it usually works.  Most times I 
can reduce 1000s of lines of code down to a 10-line example.

If you don't have time for that, I would recommend that you still post 
the bug with your complete code.  Maybe somebody else will have time. 
IMHO, it ought to be recorded.
Apr 02 2008
parent bearophile <bearophileHUGS lycos.com> writes:
Russell Lewis:

 Generally, I do binary search on my code.  I comment out huge swaths of 
 code that I think might be irrelevant, then recompile.  If the failure 
 goes away, then I only comment out half of that section, and try again.
 It's a painful, iterative process, but it usually works. Most times I 
 can reduce 1000s of lines of code down to a 10-line example.


Computers are good at performing quickly boring operations. So there are ways
to automate that. For a simple Python implementation you can look here, inside
the software of the book "Beautiful Code", subdirectory "Zeller":
http://examples.oreilly.com/9780596510046/examples.zip
Around there are better implementations of that idea, written in C too.

Bye,
bearophile
Apr 02 2008