Broken POSIX tests in the VM: SIGTSTP?

[mgree]

I'm unable to even build the POSIX test suite when running in a Vagrant VM; the TET3.8 test-suite manager complains about getting spurious TSTP signals. No such issue on Docker; issue is present in v0.1.

0|3.8-lite 22:20:49 20200210|User: vagrant (1000) TCC Start, Command line: tcc -bp vsc posix_shell
5|Linux debian9.localdomain 4.9.0-11-amd64 #1 SMP Debian 4.9.189-3+deb9u2 (2019-11-11) x86_64|System Information
20|/home/vagrant/posix/tet3.8/vsc/tetbuild.cfg 0|Config Start
30||TET_OUTPUT_CAPTURE=False
30||TET_EXPAND_CONF_VARS=true
30||TET_BUILD_TOOL=sh
30||TET_BUILD_FILE=/home/vagrant/posix/tet3.8/vsc/Bin/buildtool
30||TET_API_COMPLIANT=True
30||TET_PASS_TC_NAME=False
30||TET_VERSION=3.8-lite
40||Config End
110|0 /tset/POSIX.shell/shell/sh_04.ex 22:20:49|Build Start, scenario ref 1-0
15|0 3.8 1|TCM Start
510|0|unexpected signal 20 received by TCM
510|0 0 1 22:20:49|IC Start
510|0|unexpected signal 20 received by TCM
510|0 1 22:20:49|TP Start
510|0|unexpected signal 20 received by TCM
510|0|unexpected signal 20 received by TCM
510|0 1 7 22:20:50|NORESULT
510|0|unexpected signal 20 received by TCM
510|0 0 1 22:20:50|IC End
510|0|Abandoning test case: caught unexpected signal 20
130|0 0 22:20:50|Build End, scenario ref 1-0
110|1 /tset/POSIX.shell/shell/sh_05.ex 22:20:50|Build Start, scenario ref 2-0
15|1 3.8 1|TCM Start
510|1|unexpected signal 20 received by TCM
510|1 0 1 22:20:50|IC Start
510|1|unexpected signal 20 received by TCM
510|1 1 22:20:50|TP Start
510|1|unexpected signal 20 received by TCM
510|1|unexpected signal 20 received by TCM
510|1 1 7 22:20:51|NORESULT
510|1|unexpected signal 20 received by TCM
510|1 0 1 22:20:51|IC End
510|1|Abandoning test case: caught unexpected signal 20
130|1 0 22:20:51|Build End, scenario ref 2-0
110|2 /tset/POSIX.shell/shell/sh_06.ex 22:20:51|Build Start, scenario ref 3-0
15|2 3.8 1|TCM Start
510|2|unexpected signal 20 received by TCM
510|2 0 1 22:20:51|IC Start
510|2|unexpected signal 20 received by TCM
510|2 1 22:20:51|TP Start
510|2|unexpected signal 20 received by TCM
510|2|unexpected signal 20 received by TCM
510|2 1 7 22:20:52|NORESULT
510|2|unexpected signal 20 received by TCM
510|2 0 1 22:20:52|IC End
510|2|Abandoning test case: caught unexpected signal 20
130|2 0 22:20:52|Build End, scenario ref 3-0
110|3 /tset/POSIX.shell/shell/sh_07.ex 22:20:52|Build Start, scenario ref 4-0
15|3 3.8 1|TCM Start
510|3|unexpected signal 20 received by TCM
510|3 0 1 22:20:52|IC Start
510|3|unexpected signal 20 received by TCM
510|3 1 22:20:52|TP Start
510|3|unexpected signal 20 received by TCM
510|3|unexpected signal 20 received by TCM
510|3 1 7 22:20:53|NORESULT
510|3|unexpected signal 20 received by TCM
510|3 0 1 22:20:53|IC End
510|3|Abandoning test case: caught unexpected signal 20
130|3 0 22:20:53|Build End, scenario ref 4-0
110|4 /tset/POSIX.shell/shell/sh_08.ex 22:20:53|Build Start, scenario ref 5-0
15|4 3.8 1|TCM Start
510|4|unexpected signal 20 received by TCM
510|4 0 1 22:20:53|IC Start
510|4|unexpected signal 20 received by TCM
510|4 1 22:20:54|TP Start
510|4|unexpected signal 20 received by TCM
510|4|unexpected signal 20 received by TCM
510|4 1 7 22:20:54|NORESULT
510|4|unexpected signal 20 received by TCM
510|4 0 1 22:20:54|IC End
510|4|Abandoning test case: caught unexpected signal 20
130|4 0 22:20:54|Build End, scenario ref 5-0
110|5 /tset/POSIX.shell/shell/sh_09.ex 22:20:54|Build Start, scenario ref 6-0
15|5 3.8 1|TCM Start
510|5|unexpected signal 20 received by TCM
510|5 0 1 22:20:54|IC Start
510|5|unexpected signal 20 received by TCM
510|5 1 22:20:55|TP Start
510|5|unexpected signal 20 received by TCM
510|5|unexpected signal 20 received by TCM
510|5 1 7 22:20:55|NORESULT
510|5|unexpected signal 20 received by TCM
510|5 0 1 22:20:55|IC End
510|5|Abandoning test case: caught unexpected signal 20
130|5 0 22:20:55|Build End, scenario ref 6-0
110|6 /tset/POSIX.shell/shell/sh_10.ex 22:20:55|Build Start, scenario ref 7-0
15|6 3.8 1|TCM Start
510|6|unexpected signal 20 received by TCM
510|6 0 1 22:20:55|IC Start
510|6|unexpected signal 20 received by TCM
510|6 1 22:20:56|TP Start
510|6|unexpected signal 20 received by TCM
510|6|unexpected signal 20 received by TCM
510|6 1 7 22:20:56|NORESULT
510|6|unexpected signal 20 received by TCM
510|6 0 1 22:20:56|IC End
510|6|Abandoning test case: caught unexpected signal 20
130|6 0 22:20:56|Build End, scenario ref 7-0
110|7 /tset/POSIX.shell/shell/sh_11.ex 22:20:56|Build Start, scenario ref 8-0
15|7 3.8 1|TCM Start
510|7|unexpected signal 20 received by TCM
510|7 0 1 22:20:56|IC Start
510|7|unexpected signal 20 received by TCM
510|7 1 22:20:57|TP Start
510|7|unexpected signal 20 received by TCM
510|7|unexpected signal 20 received by TCM
510|7 1 7 22:20:57|NORESULT
510|7|unexpected signal 20 received by TCM
510|7 0 1 22:20:57|IC End
510|7|Abandoning test case: caught unexpected signal 20
130|7 0 22:20:57|Build End, scenario ref 8-0
110|8 /tset/POSIX.shell/shell/sh_12.ex 22:20:57|Build Start, scenario ref 9-0
15|8 3.8 1|TCM Start
510|8|unexpected signal 20 received by TCM
510|8 0 1 22:20:57|IC Start
510|8|unexpected signal 20 received by TCM
510|8 1 22:20:58|TP Start
510|8|unexpected signal 20 received by TCM
510|8|unexpected signal 20 received by TCM
510|8 1 7 22:20:58|NORESULT
510|8|unexpected signal 20 received by TCM
510|8 0 1 22:20:58|IC End
510|8|Abandoning test case: caught unexpected signal 20
130|8 0 22:20:58|Build End, scenario ref 9-0
110|9 /tset/POSIX.shell/shell/sh_13.ex 22:20:58|Build Start, scenario ref 10-0
15|9 3.8 1|TCM Start
510|9|unexpected signal 20 received by TCM
510|9 0 1 22:20:58|IC Start
510|9|unexpected signal 20 received by TCM
510|9 1 22:20:59|TP Start
510|9|unexpected signal 20 received by TCM
510|9|unexpected signal 20 received by TCM
510|9 1 7 22:20:59|NORESULT
510|9|unexpected signal 20 received by TCM
510|9 0 1 22:20:59|IC End
510|9|Abandoning test case: caught unexpected signal 20
130|9 0 22:20:59|Build End, scenario ref 10-0
900|22:20:59|TCC End

If the TSTP signals are my fault, I suspect it's an issue with the monitoring/interactive work in system.ml. This seems unlikely because the build was working on Linux in October.