Fix issues in libunwindstack.

- Add a load_bias field in MapInfo so that it can be loaded offline,
  and also so it can be cached.
- Add an Add function to the Maps class so that it's possible to manually
  create a map.
- Remove the OfflineMaps class since I haven't found a reason for this to
  exist.
- Add a pointer to the gnu debugdata compressed section in the interface
  itself and modify the step path to try eh_frame, then debug_frame, then
  gnu_debugdata. This way arm can add exidx as the last step behind
  gnu_debugdata. Add an offline test to verify the order of unwind.
- Fix x86_64_ucontext_t since it was a different size on 32 bit and 64 bit
  systems.

Test: Pass new unit tests.
Change-Id: I978b70d6c244bd307c62a29886d24c1a8cb2af23

1 files changed, 1 insertions, 1 deletions

diff --git a/libunwindstack/tools/unwind_info.cpp b/libunwindstack/tools/unwind_info.cpp
index a00b2ee48..7f2d11d67 100644
--- a/libunwindstack/tools/unwind_info.cpp
+++ b/libunwindstack/tools/unwind_info.cpp
@@ -87,7 +87,7 @@ void DumpDwarfSection(ElfInterface* interface, DwarfSection* section, uint64_t l
   for (const DwarfFde* fde : *section) {
     // Sometimes there are entries that have empty length, skip those since
     // they don't contain any interesting information.
-    if (fde->pc_start == fde->pc_end) {
+    if (fde == nullptr || fde->pc_start == fde->pc_end) {
       continue;
     }
     printf("\n  PC 0x%" PRIx64, fde->pc_start + load_bias);