The Guile process taking the role of PID 1 during Guix builds does not reap
zombie processes, which makes them continue responding to "kill -0".

--- a/src/testsuite/stop-server.sh	2015-02-05 11:24:00.535908842 +0100
+++ b/src/testsuite/stop-server.sh	2015-02-05 11:25:00.264351349 +0100
@@ -1,6 +1,21 @@
 #!/bin/sh
 # ngIRCd Test Suite
 
+process_is_alive(){
+    ! process_is_dead "$1" && ! process_is_undead "$1"
+}
+
+process_is_dead(){
+    ! kill -0 "$1"
+}
+
+process_is_undead(){
+    case $(ps -p "$1" -o state=) in
+        (Z*) true ;;
+        (*) false ;;
+    esac
+}
+
 [ -z "$srcdir" ] && srcdir=`dirname $0`
 
 # read in functions
@@ -24,7 +40,7 @@
 
 # waiting ...
 for i in 1 2 3 4 5; do
-  kill -0 $pid > /dev/null 2>&1; r=$?
+  process_is_alive $pid > /dev/null 2>&1; r=$?
   if [ $r -ne 0 ]; then
     echo " ok".
     exit 0
lect> <input type='submit' value='switch'/></form></td></tr>
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<div class='path'>path: <a href='/guix/log/?id=7799a01ef1b36c2a0f20ee07981bb5cd7fd64313'>root</a>/<a href='/guix/log/gnu?id=7799a01ef1b36c2a0f20ee07981bb5cd7fd64313'>gnu</a>/<a href='/guix/log/gnu/packages?id=7799a01ef1b36c2a0f20ee07981bb5cd7fd64313'>packages</a>/<a href='/guix/log/gnu/packages/graph.scm?id=7799a01ef1b36c2a0f20ee07981bb5cd7fd64313'>graph.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/graph.scm?id=7799a01ef1b36c2a0f20ee07981bb5cd7fd64313&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-06-02 13:39:13 +0200'>2018-06-02</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=7799a01ef1b36c2a0f20ee07981bb5cd7fd64313'>gnu: r-rgraphviz: Update to 2.24.0.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2018-04-21 23:07:52 +0200'>2018-04-21</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=8cf7b28ffef6ef59c8733f5e186e65967a83af3d'>gnu: r-igraph: Update to 1.2.1.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2018-03-27 03:26:46 +0200'>2018-03-27</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=ef803aa52c9cff8cc71099e2164012c328f5ebe0'>gnu: python-plotly: Update to 2.4.1.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-03-17 16:37:20 +0100'>2018-03-17</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=d062957a8797d1bd6cc44bdc94259051f42afaab'>gnu: Use HTTPS for r-project.org home pages.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-03-15 10:57:50 -0400'>2018-03-15</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=5f3616d612273e75334a37c3c94dec490271c7a5'>gnu: Add python-plotly.</a><span class='msg-avail'>...</span></td><td>Leo Famulari</td></tr>
<tr><td><span title='2018-03-02 22:23:18 +0100'>2018-03-02</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=4e35c4290ef64e8fba376f9c3d9754757ebf89da'>gnu: Add r-rbiofabric.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2017-12-18 12:01:35 +0100'>2017-12-18</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=fff9b8843918c4ab9740d9aa355506cd3d24bbc8'>gnu: Add r-diffusionmap.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2017-11-07 08:15:27 +0100'>2017-11-07</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=8ca2b2b06e69921f24808aa0cb504a18156066b6'>gnu: r-rgraphviz: Update to 2.22.0.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2017-10-22 12:12:42 +0200'>2017-10-22</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=e206de67b60d76c96eed74edf741ea9e91de4ef8'>gnu: Add r-rgraphviz.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2017-08-09 14:47:47 +0200'>2017-08-09</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=1738138cb3a48ed2f55c59c8d7c6ce12a4c4dcb3'>gnu: r-igraph: Move to (gnu packages graph).</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2017-08-09 14:47:47 +0200'>2017-08-09</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=31476df32e1d5194f4f7085bba487681cc250e38'>gnu: Add python-igraph.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2017-08-09 14:47:47 +0200'>2017-08-09</span></td><td><a href='/guix/commit/gnu/packages/graph.scm?id=e57fffad90a87d8ac38e4ac44ac5b5eb2d7bd191'>gnu: Add igraph.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>