[Sanitizer] Make StackTrace a lightweight reference to array of PCs, and

introduce a BufferedStackTrace class, which owns this array.

Summary:
This change splits __sanitizer::StackTrace class into a lightweight
__sanitizer::StackTrace, which doesn't own array of PCs, and BufferedStackTrace,
which owns it. This would allow us to simplify the interface of StackDepot,
and eventually merge __sanitizer::StackTrace with __tsan::StackTrace.

Test Plan: regression test suite.

Reviewers: kcc, dvyukov

Reviewed By: dvyukov

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5985

llvm-svn: 220635

1 files changed, 4 insertions, 7 deletions

diff --git a/compiler-rt/lib/asan/asan_debugging.cc b/compiler-rt/lib/asan/asan_debugging.cc
index ca5fa1f759f..2b66dd5265f 100644
--- a/compiler-rt/lib/asan/asan_debugging.cc
+++ b/compiler-rt/lib/asan/asan_debugging.cc
@@ -86,22 +86,19 @@ uptr AsanGetStack(uptr addr, uptr *trace, uptr size, u32 *thread_id,
   AsanChunkView chunk = FindHeapChunkByAddress(addr);
   if (!chunk.IsValid()) return 0;
 
-  StackTrace stack;
+  StackTrace stack(nullptr, 0);
   if (alloc_stack) {
     if (chunk.AllocTid() == kInvalidTid) return 0;
-    chunk.GetAllocStack(&stack);
+    stack = chunk.GetAllocStack();
     if (thread_id) *thread_id = chunk.AllocTid();
   } else {
     if (chunk.FreeTid() == kInvalidTid) return 0;
-    chunk.GetFreeStack(&stack);
+    stack = chunk.GetFreeStack();
     if (thread_id) *thread_id = chunk.FreeTid();
   }
 
   if (trace && size) {
-    if (size > kStackTraceMax)
-      size = kStackTraceMax;
-    if (size > stack.size)
-      size = stack.size;
+    size = Min(size, Min(stack.size, kStackTraceMax));
     for (uptr i = 0; i < size; i++)
       trace[i] = StackTrace::GetPreviousInstructionPc(stack.trace[i]);