Re: -ffile-prefix-map option and reproducibility

[Johannes Schauer Marin Rodrigues <josch@debian.org>]

Hi,

Quoting Stéphane Glondu (2023-02-07 16:41:47)
> When building packages, a -ffile-prefix-map option is automatically injected
> into CFLAGS. Where does it come from? Since when?

probably due to
https://git.hadrons.org/cgit/debian/dpkg/dpkg.git/commit/?id=b60c243ba99b8483202a6f6a814476275204fdff

which references:

https://lists.debian.org/debian-devel/2020/10/msg00222.html
https://bugs.debian.org/974087

> I suspect this was added to improve reproducibility. Ironically, it makes
> packages that capture this variable non reproducible, since the build path
> seems to be randomized (has it always been the case? since when?). It is the
> case of OCaml (see #1030785), and seemingly of R as well (found by grepping
> in my /etc). I wouldn't be surprised other packages are affected as well.
> 
> Is there a way to not get this option? More elegant than explicitly 
> filtering it out of CFLAGS in debian/rules...

See the man page of dpkg-buildflags -- this might do what you want:

export DEB_BUILD_MAINT_OPTIONS=reproducible=-fixfilepath

Thanks!

cheers, josch