Re: ar "zero" flag

["Greg A. Woods; Planix, Inc." <woods%planix.ca@localhost>]

On 7-Aug-08, at 7:10 AM, Perry E. Metzger wrote:
> A small request: could we use a second "subject" line to discuss
> getting rid of .a files altogether? I'd like to keep the topics
> separate, given that I have to make something work for 5.0 and .a
> files will certainly be in 5.0...


I really do like the idea of being able to rebuild binaries that are  
bit-for-bit identical regardless of when or where they are built.  Or  
at least I like the idea of being able to compare any similar object  
file types and determine that they are in fact identical in all ways  
which could possibly affect their eventual execution as machine code.

This zeroing of timesstamps does seem to be the most elegant idea vs.  
the as yet never appeared idea of a diff/cmp-like tool that's aware of  
the inner structure of various object file types.  However such a tool  
would also suffice for my needs of comparing binaries, and it would  
potentially also have far more utility than a simple flag to eliminate  
timestamps from object archives would have.  Note that such a tool  
could also be used to generate data for cryptographic signing if it  
were to have a mode where it would act like "cat" but zero out  
irrelevant non-executable non-data sections as it copied them  
through.  I don't think use of such a tool would in any way decrease  
the level of trust one should have in the result.

I'm not so sure I like '0' as the date value to be used to eliminate  
timestamp information from object archives.  I did kind of like the  
0xDEADBEEF idea.  Zero though might work best with any version of  
"make" as-is.

--
                                        Greg A. Woods; Planix, Inc.
                                        <woods%planix.ca@localhost>