From e22701ee8a8246e9648a60ebdbed2c415c103c91 Mon Sep 17 00:00:00 2001
From: Josh Gao <jmgao@google.com>
Date: Mon, 23 Oct 2017 14:25:08 -0700
Subject: [PATCH] libbacktrace: remove exit time destructors.

If libbacktrace is statically linked into a library that interposes
libc, exit-time destructors can lead to a segfault upon exit if static
variables are used after their destruction.

Remove the one use of a static variable (with inconsequential
performance impact of less than 1us per backtrace), and enable
-Wexit-time-destructors to ensure this stays fixed in the future.

Test: mma
Change-Id: Icdaf1cf1c1f166cf501d9ecd1983c44e4305f7e9
---
 libbacktrace/Android.bp      | 4 ++++
 libbacktrace/UnwindStack.cpp | 2 +-
 libunwindstack/Android.bp    | 4 ++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/libbacktrace/Android.bp b/libbacktrace/Android.bp
index ed1018302..0b2ce1dff 100644
--- a/libbacktrace/Android.bp
+++ b/libbacktrace/Android.bp
@@ -73,6 +73,10 @@ cc_library {
     defaults: ["libbacktrace_common"],
     host_supported: true,
 
+    cflags: [
+        "-Wexit-time-destructors",
+    ],
+
     srcs: [
         "BacktraceMap.cpp",
     ],
diff --git a/libbacktrace/UnwindStack.cpp b/libbacktrace/UnwindStack.cpp
index 62e453fb8..d17c211d0 100644
--- a/libbacktrace/UnwindStack.cpp
+++ b/libbacktrace/UnwindStack.cpp
@@ -45,7 +45,7 @@
 
 bool Backtrace::Unwind(unwindstack::Regs* regs, BacktraceMap* back_map,
                        std::vector<backtrace_frame_data_t>* frames, size_t num_ignore_frames) {
-  static std::vector<std::string> skip_names{"libunwindstack.so", "libbacktrace.so"};
+  std::vector<std::string> skip_names{"libunwindstack.so", "libbacktrace.so"};
   UnwindStackMap* stack_map = reinterpret_cast<UnwindStackMap*>(back_map);
   auto process_memory = stack_map->process_memory();
   unwindstack::Unwinder unwinder(MAX_BACKTRACE_FRAMES + num_ignore_frames, stack_map->stack_maps(),
diff --git a/libunwindstack/Android.bp b/libunwindstack/Android.bp
index e687a6895..c885c3f9b 100644
--- a/libunwindstack/Android.bp
+++ b/libunwindstack/Android.bp
@@ -65,6 +65,10 @@ cc_library {
         "Symbols.cpp",
     ],
 
+    cflags: [
+        "-Wexit-time-destructors",
+    ],
+
     target: {
         // Always disable optimizations for host to make it easier to debug.
         host: {