From: Colin Watson <cjwatson@debian.org>
Date: Tue, 27 Aug 2019 05:55:40 +0000 (+0100)
Subject: man-db 2.8.7
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~cjwatson/git?a=commitdiff_plain;h=3f74c6f718eb56098116c98ebf479d81a4bd2d56;p=blog.git

man-db 2.8.7
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+Title: man-db 2.8.7
+Slug: man-db-2.8.7
+Date: 2019-08-27 06:55:25 +01:00
+Category: man-db
+Tags: man-db, planet-debian, planet-ubuntu
+
+I've released man-db 2.8.7
+([announcement](https://lists.nongnu.org/archive/html/man-db-announce/2019-08/msg00002.html),
+[NEWS](http://git.savannah.gnu.org/cgit/man-db.git/tree/NEWS?id=2.8.7)),
+and uploaded it to Debian unstable.
+
+There are a few things of note that I wanted to talk about here.  Firstly, I
+made some further improvements to the seccomp sandbox originally introduced
+in 2.8.0.  I do still think it's correct to try to confine subprocesses this
+way as a defence against malicious documents, but it's also been a pretty
+rough ride for some users, especially those who use various kinds of VPNs or
+antivirus programs that install themselves using `/etc/ld.so.preload` and
+cause other programs to perform additional system calls.  As well as a few
+specific tweaks, a [recent discussion on
+LWN](https://lwn.net/Articles/796108/) reminded me that it would be better
+to make seccomp return `EPERM` rather than raising `SIGSYS`, since that's
+easier to handle gracefully: in particular, it fixes [an odd corner case
+related to glibc's nscd handling](https://bugs.debian.org/902257).
+
+Secondly, there was a [build failure on
+macOS](https://savannah.nongnu.org/bugs/?56734) that took a while to figure
+out, not least because I don't have a macOS test system myself.  In 2.8.6 I
+tried to make life easier for people on this platform with a [`CFLAGS`
+tweak](https://git.savannah.gnu.org/cgit/man-db.git/commit/?id=056e8c7c012b00261133259d6438ff8303a8c36c),
+but I made it a bit too general and accidentally took away configure's
+ability to detect undefined symbols properly, which caused very confusing
+failures.  More importantly, I hadn't really thought through why this change
+was necessary and whether it was a good idea.  man-db uses private shared
+libraries to keep its executable size down, and it passes `-no-undefined` to
+`libtool` to declare that those shared libraries have no undefined symbols
+after linking, which is necessary to build shared libraries on some
+platforms.  But the `CFLAGS` tweak above directly contradicts this!  So,
+instead of playing core wars with my own build system, I did some
+refactoring so that the assertion that man-db's shared libraries have no
+undefined symbols after linking is actually true: this involved [moving
+decompression code out of
+`libman`](https://git.savannah.gnu.org/cgit/man-db.git/commit/?id=2519d2ffe769a4059bfe475a092afa40722eb38d),
+and arranging for the code in `libmandb` to take the database path as a
+parameter rather than as a global variable (something I've meant to fix for
+ages anyway;
+[252d7cbc23](https://git.savannah.gnu.org/cgit/man-db.git/commit/?id=252d7cbc2328b27457aafcbd6fa5958a8be9fded),
+[036aa910ea](https://git.savannah.gnu.org/cgit/man-db.git/commit/?id=036aa910ea000d716bcf0f4bcbcee3a54a848be7),
+[a97d977b0b](https://git.savannah.gnu.org/cgit/man-db.git/commit/?id=a97d977b0bfc1ed34c3021b8d6702b047e8251af)).
+Lesson: don't make build system changes you don't quite understand.