[Reproducible-builds] New default -fdebug-prefix-map build flag for dpkg

[Mattia Rizzolo]

On Mon, Jul 18, 2016 at 08:57:01AM +0000, Mattia Rizzolo wrote:
> Hi *,
> 
> As part of the Reproducible Builds effort [0], we would like to enable
> a new default build flag from the reproducible/fixdebugpath feature
> area in order to prevent issues with build paths.

[...]

> clang 3.8 supports the build flag and does not save the path in
> DW_AT_producer (although the source path gets included in the .strtab
> section if the source path is passed absolutely).  We asked [3] the
> clang maintainers whether they would be willing to backport the
> -fdebug-prefix-path, but in the worst case there are only 3 clang
> reverse build-deps FTBFS due to this [4].

[...]

> We enabled the reproducible/fixdebugpath feature in the Reproducible
> Builds CI one month ago and whilst we have about 3k packages yet to
> build we are already confident that there won't be any major regression
> related to this other than those 3 packages.

We have now completed the rebuild, and the packages FTBFSing with this
new build flag are these:
 - afl #828178
 - libblocksruntime #832015
 - libclc # 832014
 - ncl #832011
 - clustalx #832013
 - clonalframe #832012

The first 3 are due to clan 3.7 not supporting the build flag, so it's
either clang being fixed (#819185) , or packages workarounding it.

> Thus, following the dpkg team's policy [5] about adding a new default
> build flag, I'm seeking a wider discussion to see whether somebody has
> any concern we haven't already taken care of.

I think the failing packages are nothing particularly interesting, and
it's very easy to fix, so if no concerns arise in the next very few
days, I'm going to open a bug to dpkg to have the build flag turned on
by default.

-- 
regards,
                        Mattia Rizzolo

GPG Key: 66AE 2B4A FCCF 3F52 DA18  4D18 4B04 3FCD B944 4540      .''`.
more about me:  https://mapreri.org                             : :'  :
Launchpad user: https://launchpad.net/~mapreri                  `. `'`
Debian QA page: https://qa.debian.org/developer.php?login=mattia  `-
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