[src/trunk]: src/lib/libexecinfo make the backtrace()'s tracer() return _URC_...

[mrg <mrg%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/4c4aa68696f7
branches:  trunk
changeset: 448014:4c4aa68696f7
user:      mrg <mrg%NetBSD.org@localhost>
date:      Wed Jan 30 22:46:49 2019 +0000

description:
make the backtrace()'s tracer() return _URC_FOREIGN_EXCEPTION_CAUGHT
when the array is full.  it won't be able to do any more work if so,
and avoids infinite loops in unwinding as seen on arm64.

XXX:  lack of signal support here means that backtrace() is useless
XXX:  from a signal handler, such as attempting to display the stack
XXX:  when handling a SIGSEGV.

diffstat:

 lib/libexecinfo/unwind.c |  4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diffs (18 lines):

diff -r e3189313e0b9 -r 4c4aa68696f7 lib/libexecinfo/unwind.c
--- a/lib/libexecinfo/unwind.c  Wed Jan 30 20:20:36 2019 +0000
+++ b/lib/libexecinfo/unwind.c  Wed Jan 30 22:46:49 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: unwind.c,v 1.2 2014/03/24 21:26:01 joerg Exp $ */
+/*     $NetBSD: unwind.c,v 1.3 2019/01/30 22:46:49 mrg Exp $   */
 
 /*-
  * Copyright (c) 2012 The NetBSD Foundation, Inc.
@@ -52,6 +52,8 @@
        }
        if (t->n < t->len)
                t->arr[t->n++] = (void *)_Unwind_GetIP(ctx);
+       else
+               return _URC_FOREIGN_EXCEPTION_CAUGHT;
        return 0;
 }