llvm dev - Dec 2010 - [LLVMdev] question on generating dwarf metadata

I am writing a front end for a new language and am having trouble generating 
the DWARF debugging information.  I'm outputting llvm assembly source so
I'm
trying to generate the "!metadata" stuff.

I have found the document <http://llvm.org/docs/SourceLevelDebugging.html>
a
helpful start, as far as it goes.  However, it doesn't quite match what I
see
clang produce when I use the flags "clang -g -S -emit-llvm ..." in all
cases.
And it is incomplete, for example, how does one deal with a function that 
returns multiple values?

I seem to get different results when I feed the .ll file to llc than when I 
feed it the clang, clang gives error messages when it doesn't like the
metadata
structure, llc appears not to do so.

Is there another document I should look at?

Should I be looking at source code?  Where are the structures that start with 
DW_TAG's parsed?

In general, what's resources does a front end implementer have in order to 
understand how to generate the DWARF stuff via llvm assembly source?

thanks, bagel

On Dec 3, 2010, at 2:39 PM, Bagel wrote:
> I am writing a front end for a new language and am having trouble
generating
> the DWARF debugging information.  I'm outputting llvm assembly source
so I'm
> trying to generate the "!metadata" stuff.
> 
> I have found the document
<http://llvm.org/docs/SourceLevelDebugging.html> a
> helpful start, as far as it goes.  However, it doesn't quite match what
I see
> clang produce when I use the flags "clang -g -S -emit-llvm ..."
in all cases.
> And it is incomplete, for example, how does one deal with a function that 
> returns multiple values?
> 
> I seem to get different results when I feed the .ll file to llc than when I
> feed it the clang, clang gives error messages when it doesn't like the
metadata
> structure, llc appears not to do so.
> 
> Is there another document I should look at?
> 
> Should I be looking at source code?  Where are the structures that start
with
> DW_TAG's parsed?
> 
> In general, what's resources does a front end implementer have in order
to
> understand how to generate the DWARF stuff via llvm assembly source?

We are working on a document. Here is current draft:
	http://wiki.llvm.org/Debug_Information

-
Devang

On 4 December 2010 00:28, Devang Patel <dpatel at apple.com>
wrote:
> We are working on a document. Here is current draft:
>        http://wiki.llvm.org/Debug_Information
Hi Devang,

Do you think we should keep updating the wiki or in the HTML? Do we
need this doc to be in the release docs?

cheers,
--renato

On 12/03/2010 06:28 PM, Devang Patel wrote:
> We are working on a document. Here is current draft:
> 	http://wiki.llvm.org/Debug_Information
>
> -
> Devang
While this is great news, it doesn't completely satisfy my needs.  Your 
documentation assumes one is going to use the LLVM provided functions 
(such as DIFactory::).  My front-end can't use them because it is not 
written in C or C++.  I need to know the exact layouts of the LLVM 
assembly metadata -- the textual form -- and what the fields mean.  The 
comments in your examples are close.

Perhaps you can add another section just on the textual format?

thanks, bagel