[LLVMdev] "Cannot fine DIE"

[Talin]

On Mon, Aug 23, 2010 at 5:58 PM, Devang Patel <devang.patel at gmail.com>wrote:

>
> On Sun, Aug 22, 2010 at 12:50 PM, Talin <viridia at gmail.com> wrote:
>
>> I recently started getting this error when I try to debug my LLVM-compiled
>> program in GDB:
>>
>>     Dwarf Error: Cannot find DIE at 0x16769 referenced from DIE at 0x1713c
>> [in module
>> /home/talin/Projects/tart/build-eclipse/test/stdlib/ReflectionTest]
>>
>> I'm not sure if it's something I did or not. Is there any way to track
>> down the cause of this error? The hex addresses in the error message are
>> meaningless to me.
>>
>
> There is not much info here. The error says one debug info entry (DIE) is
> referring to another debug info entry that does not exist. This usually
> indicates that dwarf generator in llvm codegen knew about the other DIE but
> some how gdb does not find the DIE. May be the code generator did not emit
> the DIE ? If yes then why ?  Otherwise, the DIE was dropped somewhere after
>  compiler generated code.
>
> I've discovered a little bit more, but not enough to solve the problem.

Here's what my code looks like for setting the debug location (some details
removed for clarity):

void CodeGenerator::setDebugLocation(const SourceLocation & loc) {
  if (loc != dbgLocation_ && dbgContext_.isScope()) {
    dbgLocation_ = loc;
    if (loc.file == NULL) {
      builder_.SetCurrentDebugLocation(llvm::DebugLoc());
    } else if (loc.file == module_->moduleSource()) {
      TokenPosition pos = tokenPosition(loc);
      // ** Comment out this line and the DIE errors disappear **
      builder_.SetCurrentDebugLocation(
          DebugLoc::get(pos.beginLine, pos.beginCol, dbgContext_));
    }
  }
}

As noted in the comment above, if I comment out the line that calls
builder_.SetCurrentDebugLocation(), then gdb no longer reports not being
able to find the DIE. Of course, I don't get any source-line debugging
information either.

Note that even in this case, I'm still generating tons of DWARF info for
data types, files, functions, and so on. This all apparently works (or at
least, it doesn't seem to generate this particular problem). It's only the
generating of source line information that causes the error. This is
fortunate, since as you can see the code is quite trivial, whereas I was
afraid that if the problem was in the data type code, it would take forever
to locate the problem as that code is pretty complicated.

As far as why this code is causing the error, I can only guess that I am
calling it wrong somehow. But I can't think what I could do differently from
what I am doing already.


> -
> Devang
>



-- 
-- Talin
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