[PATCH] signal: work around Haiku issue with SIGBUS

[Eric Blake]

* lib/siglist.h: Add comment.
* lib/sig2str.c (numname_table): Swap SIGBUS order, to match
strsignal's favoring of SIGSEGV.
* tests/test-signal.c (main): Avoid test failure.
* doc/posix-headers/signal.texi (signal.h): Document the issue.
Reported by Scott McCreary.

Signed-off-by: Eric Blake <address@hidden>
---

> Thanks for tracking that.  In glancing through gnulib uses of SIGBUS, it
> looks like most are harmless (it may end up associating the same handler
> with SIGSEGV twice in a row), but at least tests/test-signal.c will fail
> if we don't modify it to account for this bug.  Also, we want to favor
> the name SIGSEGV in lists like strsignal(SIGBUS).  And documenting the
> bug can't hurt.  Patch coming up shortly.

I don't have access to Haiku, or I would test this.  Does it look okay?

 ChangeLog                     |    8 ++++++++
 doc/posix-headers/signal.texi |    4 ++++
 lib/sig2str.c                 |   10 ++++++----
 lib/siglist.h                 |    3 +++
 tests/test-signal.c           |    3 ++-
 5 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 12ab93b..38c4065 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2010-12-31  Eric Blake  <address@hidden>

+       signal: work around Haiku issue with SIGBUS
+       * lib/siglist.h: Add comment.
+       * lib/sig2str.c (numname_table): Swap SIGBUS order, to match
+       strsignal's favoring of SIGSEGV.
+       * tests/test-signal.c (main): Avoid test failure.
+       * doc/posix-headers/signal.texi (signal.h): Document the issue.
+       Reported by Scott McCreary.
+
        nl_langinfo: fix YESEXPR on Irix 6.5
        * m4/nl_langinfo.m4 (gl_FUNC_NL_LANGINFO): Test for Irix bug.
        * lib/nl_langinfo.c (rpl_nl_langinfo): Work around it.
diff --git a/doc/posix-headers/signal.texi b/doc/posix-headers/signal.texi
index 9056d1e..77a5432 100644
--- a/doc/posix-headers/signal.texi
+++ b/doc/posix-headers/signal.texi
@@ -39,4 +39,8 @@ signal.h
 The macros @code{SIGRTMIN} and @code{SIGRTMAX} expand to an expression of type
 @code{long} instead of @code{int} on some platforms:
 OSF/1 5.1.
address@hidden
+The macro @code{SIGBUS} is set to the same value as @code{SIGSEGV},
+rather than being a distinct signal, on some platforms:
+Haiku.
 @end itemize
diff --git a/lib/sig2str.c b/lib/sig2str.c
index fce22c0..99167cf 100644
--- a/lib/sig2str.c
+++ b/lib/sig2str.c
@@ -41,7 +41,7 @@
 static struct numname { int num; char const name[8]; } numname_table[] =
   {
     /* Signals required by POSIX 1003.1-2001 base, listed in
-       traditional numeric order.  */
+       traditional numeric order where possible.  */
 #ifdef SIGHUP
     NUMNAME (HUP),
 #endif
@@ -66,12 +66,14 @@ static struct numname { int num; char const name[8]; } 
numname_table[] =
 #ifdef SIGKILL
     NUMNAME (KILL),
 #endif
-#ifdef SIGBUS
-    NUMNAME (BUS),
-#endif
 #ifdef SIGSEGV
     NUMNAME (SEGV),
 #endif
+    /* On Haiku, SIGSEGV == SIGBUS, but we prefer SIGSEGV to match
+       strsignal.c output, so SIGBUS must be listed second.  */
+#ifdef SIGBUS
+    NUMNAME (BUS),
+#endif
 #ifdef SIGPIPE
     NUMNAME (PIPE),
 #endif
diff --git a/lib/siglist.h b/lib/siglist.h
index e372429..4783fa6 100644
--- a/lib/siglist.h
+++ b/lib/siglist.h
@@ -24,6 +24,9 @@

 /* This file is included multiple times.  */

+/* Duplicate values (such as SIGBUS==SIGSEGV on Haiku) favor the last
+   list entry.  */
+
 /* Standard signals  */
 #ifdef SIGHUP
   init_sig (SIGHUP, "HUP", N_("Hangup"))
diff --git a/tests/test-signal.c b/tests/test-signal.c
index 71c6061..3e759d7 100644
--- a/tests/test-signal.c
+++ b/tests/test-signal.c
@@ -59,7 +59,8 @@ main (void)
 #ifdef SIGALRM
     case SIGALRM:
 #endif
-#ifdef SIGBUS
+      /* On Haiku, SIGBUS is mistakenly equal to SIGSEGV.  */
+#if defined SIGBUS && SIGBUS != SIGSEGV
     case SIGBUS:
 #endif
 #ifdef SIGCHLD
-- 
1.7.3.4