Copy in libbacktrace from gcc

This copies in libbacktrace from the gcc repository as it was in the
commit 62e420293a293608f383d9b9c7f2debd666e9fc9.  GDB is going to
start using this library soon.

A dependency between GDB and libbacktrace has already been added to
the top level Makefile, so, after this commit, when building GDB,
libbacktrace will be built first.  However, libbacktrace is not yet
linked into GDB, or used by GDB in any way.

It is possible to stop libbacktrace being built by configuring the
tree with --disable-libbacktrace.

This commit does NOT update src-release.sh, that will be done in the
next commit, this commit ONLY imports libbacktrace from gcc.  This
means that if you try to make a release of GDB from exactly this
commit then the release tar file will not include libbacktrace.
However, as libbacktrace is an optional dependency this is fine.

1 files changed, 66 insertions, 0 deletions

diff --git a/libbacktrace/nounwind.c b/libbacktrace/nounwind.c
new file mode 100644
index 0000000..0eea713
--- /dev/null
+++ b/libbacktrace/nounwind.c
@@ -0,0 +1,66 @@
+/* backtrace.c -- Entry point for stack backtrace library.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
+   Written by Ian Lance Taylor, Google.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    (1) Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+    (2) Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in
+    the documentation and/or other materials provided with the
+    distribution.
+
+    (3) The name of the author may not be used to
+    endorse or promote products derived from this software without
+    specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.  */
+
+#include "config.h"
+
+#include <sys/types.h>
+
+#include "backtrace.h"
+
+#include "internal.h"
+
+/* This source file is compiled if the unwind library is not
+   available.  */
+
+int
+backtrace_full (struct backtrace_state *state ATTRIBUTE_UNUSED,
+		int skip ATTRIBUTE_UNUSED,
+		backtrace_full_callback callback ATTRIBUTE_UNUSED,
+		backtrace_error_callback error_callback, void *data)
+{
+  error_callback (data,
+		  "no stack trace because unwind library not available",
+		  0);
+  return 0;
+}
+
+int
+backtrace_simple (struct backtrace_state *state ATTRIBUTE_UNUSED,
+		  int skip ATTRIBUTE_UNUSED,
+		  backtrace_simple_callback callback ATTRIBUTE_UNUSED,
+		  backtrace_error_callback error_callback, void *data)
+{
+  error_callback (data,
+		  "no stack trace because unwind library not available",
+		  0);
+  return 0;
+}