setting -fdebug-prefix-map via envvar

[Bill Allombert]

On Fri, Jun 26, 2020 at 12:51:33PM +0100, Chris Lamb wrote:
> Bill Allombert wrote:
> 
> > The issue is that adding -fdebug-prefix-map=PREFIX to CFLAGS
> > leads to PREFIX leaking in buildlogs and in generated Makefiles and
> > similar files that can end up inside packages, making previously
> > reproducible packages unreproducible.
> 
> Let's all take a step back for a second before we get into specific
> solutions that might just be papering over the problem.
> 
> Can you just clarify the exact context and/or use-case here? I ask
> because -fdebug-prefix-map is usually set via CFLAGS via
> dpkg-buildflags (rather than manually, as your use of the word
> "adding" could be implying).
> 
> Indeed, Debian packages should be respecting flags set from via the
> dpkg-buildflags mechanism, so specifically asking about
> -fdebug-prefix-map at all sounds like something else is going and we
> aren't asking the right question here yet.

How exactly -fdebug-prefix-map=PREFIX is added to CFLAGS is irrelevant.
What matters is that the value of CFLAGS is now different from build to
build. When this value is included inside a binary package for whatever
reasons, then the package is no longer reproducible.

Cheers,
-- 
Bill. <ballombe at debian.org>

Imagine a large red swirl here.