[PATCH] tests: Skip signal detection on Haiku

[Eric Blake]

On Haiku, using 'kill -9' fromm /bin/shactually causes a process to
die with the non-standard SIGKILLTHR 15, which causes 198.sysval to
fail from the unexpected value.

* doc/m4.texi (Sysval): Skip test on Haiku.
Reported by Bruno Haible,
https://lists.gnu.org/archive/html/bug-m4/2021-05/msg00004.html
---
 doc/m4.texi | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/doc/m4.texi b/doc/m4.texi
index 7dcbb5ce..94ac851d 100644
--- a/doc/m4.texi
+++ b/doc/m4.texi
@@ -6745,14 +6745,22 @@ Sysval
 @comment systems where /bin/sh does not create its own process group.
 @comment And PIPE is unreliable, since people tend to run with it
 @comment ignored, with m4 inheriting that choice.  That leaves KILL as
-@comment the only signal we can reliably test.
+@comment the only signal we can reliably test, but even that is tricky:
+@comment on Haiku, 'kill -9' actually causes a process to die with
+@comment signal 15 named KILLTHR on that platform.
 @example
 dnl This test assumes kill is a shell builtin, and that signals are
 dnl recognizable.
 ifdef(`__unix__', ,
       `errprint(` skipping: syscmd does not have unix semantics
 ')m4exit(`77')')dnl
-syscmd(`kill -9 $$')
+changequote(`[', `]')
+@result{}
+syscmd([/bin/sh -c 'kill -9 $$'; st=$?; test $st = 137 || test $st = 265])
+@result{}
+ifelse(sysval, [0], , [errprint([ skipping: shell does not send signal 9
+])m4exit([77])])dnl
+syscmd([kill -9 $$])
 @result{}
 sysval
 @result{}2304
@@ -6760,7 +6768,7 @@ Sysval
 @result{}
 sysval
 @result{}0
-esyscmd(`kill -9 $$')
+esyscmd([kill -9 $$])
 @result{}
 sysval
 @result{}2304
-- 
2.31.1