Fix build issue with libpng

[embray]

I just noticed this small bug in the DESTDIR build support for libpng. This might explain why I and others sometimes have build problems surrounding libpng.

This symlink should get deleted before it's installed in $SAGE_LOCAL. Otherwise it takes a re-installation of libpng in order to force the symlink to be removed.

Upstream: Fixed upstream, but not in a stable release.

Component: packages: standard

Author: Erik Bray

Branch/Commit: afb74b9

Reviewer: Julian Rüth

Issue created by migration from https://trac.sagemath.org/ticket/25818

[embray]

comment:2

Fixing this (and in some cases also not fixing it) seems to break giac, which is linking with -lpng instead of -lpng16.

That would explain some of the spurious patchbot build failures I've been seeing.

[embray]

comment:3

Hmm, it seems we need to patch giac.

[sagetrac-git]

Changed commit from 5e10555 to afb74b9

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

afb74b9

patch giac's configure script to ensure it uses -lpng16 where available

[embray]

comment:5

Adds a patch to giac to ensure that it links against -lpng16 when available, rather than -lpng.

Amusingly, almost the correct incantation, albeit a bit misspelled, was already in its configure.in but commented out.

[embray]

Upstream: Not yet reported upstream; Will do shortly.

[embray]

comment:7

I e-mailed the upstream patch to Bernard Parisse.

[embray]

Changed upstream from Not yet reported upstream; Will do shortly. to Reported upstream. No feedback yet.

[embray]

comment:8

I guess?

Hi,

Thanks for the patch, it will be included in the next releases.

[embray]

Changed upstream from Reported upstream. No feedback yet. to Fixed upstream, but not in a stable release.

[saraedum]

Reviewer: Julian Rüth

[embray]

comment:10

Several patchbots appear to be in some kind of broken state. I don't think it's due to this ticket; rather their owners should probably reset them.

[embray]

comment:11

I believe this issue can reasonably be addressed for Sage 8.4.

[vbraun]

Changed branch from u/embray/build/libpng/symlinks to afb74b9