From 4ffa98388f8a28c55b0c8acfbba5f62df954c2a4 Mon Sep 17 00:00:00 2001
From: Sergiu Deitsch <sergiu.deitsch@gmail.com>
Date: Tue, 21 Dec 2021 10:47:24 +0100
Subject: [PATCH] ensure _Unwind_Backtrace to actually be available

---
 CMakeLists.txt                                           | 4 ++++
 bazel/glog.bzl                                           | 2 +-
 src/config.h.cmake.in                                    | 3 +++
 src/{stacktrace_x86_64-inl.h => stacktrace_unwind-inl.h} | 0
 src/utilities.h                                          | 4 ++--
 5 files changed, 10 insertions(+), 3 deletions(-)
 rename src/{stacktrace_x86_64-inl.h => stacktrace_unwind-inl.h} (100%)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f166f7b..8cce87d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -94,6 +94,10 @@ if (Unwind_FOUND)
   set (HAVE_LIB_UNWIND 1)
 else (Unwind_FOUND)
   check_include_file_cxx (unwind.h HAVE_UNWIND_H)
+  # Check whether linking actually succeeds. ARM toolchains of LLVM unwind
+  # implementation do not necessarily provide the _Unwind_Backtrace function
+  # which causes the previous check to succeed but the linking to fail.
+  check_cxx_symbol_exists (_Unwind_Backtrace unwind.h HAVE__UNWIND_BACKTRACE)
 endif (Unwind_FOUND)
 
 check_include_file_cxx (dlfcn.h HAVE_DLFCN_H)
diff --git a/bazel/glog.bzl b/bazel/glog.bzl
index 1392bfb..43a2637 100644
--- a/bazel/glog.bzl
+++ b/bazel/glog.bzl
@@ -128,9 +128,9 @@ def glog_library(namespace = "google", with_gflags = 1, **kwargs):
             "src/stacktrace_generic-inl.h",
             "src/stacktrace_libunwind-inl.h",
             "src/stacktrace_powerpc-inl.h",
+            "src/stacktrace_unwind-inl.h",
             "src/stacktrace_windows-inl.h",
             "src/stacktrace_x86-inl.h",
-            "src/stacktrace_x86_64-inl.h",
             "src/symbolize.cc",
             "src/symbolize.h",
             "src/utilities.cc",
diff --git a/src/config.h.cmake.in b/src/config.h.cmake.in
index ca278ad..b225b7e 100644
--- a/src/config.h.cmake.in
+++ b/src/config.h.cmake.in
@@ -118,6 +118,9 @@
 /* Define if you have the <unwind.h> header file. */
 #cmakedefine HAVE_UNWIND_H
 
+/* Define if you linking to _Unwind_Backtrace is possible. */
+#cmakedefine HAVE__UNWIND_BACKTRACE
+
 /* define if the compiler supports using expression for operator */
 #cmakedefine HAVE_USING_OPERATOR
 
diff --git a/src/stacktrace_x86_64-inl.h b/src/stacktrace_unwind-inl.h
similarity index 100%
rename from src/stacktrace_x86_64-inl.h
rename to src/stacktrace_unwind-inl.h
diff --git a/src/utilities.h b/src/utilities.h
index bd818dc..1f55eff 100644
--- a/src/utilities.h
+++ b/src/utilities.h
@@ -88,8 +88,8 @@
 
 #if defined(HAVE_LIB_UNWIND)
 # define STACKTRACE_H "stacktrace_libunwind-inl.h"
-#elif defined(HAVE_UNWIND_H)
-# define STACKTRACE_H "stacktrace_x86_64-inl.h"
+#elif defined(HAVE__UNWIND_BACKTRACE)
+# define STACKTRACE_H "stacktrace_unwind-inl.h"
 #elif !defined(NO_FRAME_POINTER)
 # if defined(__i386__) && __GNUC__ >= 2
 #  define STACKTRACE_H "stacktrace_x86-inl.h"