Re: [gentoo-soc] libbash Weekly Update

[Luca Barbato]

On 07/19/2010 05:46 PM, Nathan Eloe wrote:
> I've had a productive week overall, with lots of good progress towards
> the final goal of this project.
>
> As the grammar becomes finalized, a change must be made.  All of the
> debugging tools are used for grammars that output Java code, but I want
> a C/C++ library to handle everything.  So this meant the following things:
> 1) Grammar file had to work regardless of what the output language was.
> 2) I needed to know just how the C runtime worked for ANTLR.
> 3) Since I'm starting to write library code (not just a grammar in a
> fancy IDE) I need to document my coding standards for any C/C++ code
> written over the next half of the project.
>
> And that indeed is what I've done.  I now have coding style guidelines
> (which can be found at http://web.mst.edu/~nwe5g8/coding_standard.pdf,
> though as changes are made to the .tex file in the repository, the
> guaranteed up to date version of the guidelines can be generated from that).
>
> Also, I've written a quick sample program that parses a single ebuild.
> This is mostly a proof of concept, not a final product.  All I was
> trying to do was get familiar with the C runtime and see how it worked.
>
> In a previous email I wrote about "infinite loops" in the parser, or at
> least loops that I was too impatient to wait to finish (5 minutes is too
> long to wait for a parser to finish parsing something).  I found the
> problem: I was attempting to recursively aggregate complex strings in
> the parser, and the backtracking became too complex for it to handle.
> So, I removed the aggregation step, instead just showing the individual
> portions of the strings.  Aggregation will be handled by the C++
> implementation (which has to do other things with variable expansions in
> strings, etc).  So that was a major problem solved, and it tuned the
> performance of the parser quite nicely.
>
> The last thing I needed to do was get a language agnostic grammar.  C++
> already has functions like exp, and bitor, bitxor, and bitand are C++
> keywords.  The runtime doesn't do anything to fix/catch any of this.  As
> such I had to go back and do that manually.  However, the changes I made
> seemed to make it a grammar that was easier to read.
>
>
> This week is mostly setup and input.  I'm writing a big bash script that
> demonstrates all the features that the grammar supports, and will be
> sending the resulting AST to the bash upstream mailing list and the
> portage_devs mailing list to see if they have suggestions.  I'm also
> going to scour man bash for missing features, set up the build system
> for the libbash portion of the code (most likely cmake), Implement a
> very simple bash builtin (echo), and finally implement a symbol table.
> A busy week, but a week that should leave me in excellent shape for the
> rest of the project.

If it has to be used in portage please:

- use autotools or ask for help about using them.
- consider staying on plain C as much as possible, breakage in C++
software because of tiny differences in the stdc++ runtime are a
constant and portage must survive them.

lu

-- 

Luca Barbato
Gentoo/linux
http://dev.gentoo.org/~lu_zero