[compiler-rt] [HWASan] leave BufferedStackTrace uninit

[fmayer]

Otherwise we have to memset 2040 bytes (255 * 8) for each call to a
malloc-like function.

This caused noticable slowdown on AOSP.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Florian Mayer (fmayer)

Changes

Otherwise we have to memset 2040 bytes (255 * 8) for each call to a
malloc-like function.

This caused noticable slowdown on AOSP.

---

Full diff: https://github.com/llvm/llvm-project/pull/102247.diff

1 Files Affected:

• (modified) compiler-rt/lib/hwasan/hwasan.h (+4-4)

diff --git a/compiler-rt/lib/hwasan/hwasan.h b/compiler-rt/lib/hwasan/hwasan.h
index df21375e81671..b918368fe8658 100644
--- a/compiler-rt/lib/hwasan/hwasan.h
+++ b/compiler-rt/lib/hwasan/hwasan.h
@@ -139,15 +139,15 @@ void hwasan_free(void *ptr, StackTrace *stack);
 void InstallAtExitHandler();
 
 #define GET_MALLOC_STACK_TRACE                                            \
-  BufferedStackTrace stack;                                               \
+  __attribute__((uninitialized)) BufferedStackTrace stack;                \
   if (hwasan_inited)                                                      \
     stack.Unwind(StackTrace::GetCurrentPc(), GET_CURRENT_FRAME(),         \
                  nullptr, common_flags()->fast_unwind_on_malloc,          \
                  common_flags()->malloc_context_size)
 
-#define GET_FATAL_STACK_TRACE_PC_BP(pc, bp)              \
-  BufferedStackTrace stack;                              \
-  if (hwasan_inited)                                     \
+#define GET_FATAL_STACK_TRACE_PC_BP(pc, bp)                \
+  __attribute__((uninitialized)) BufferedStackTrace stack; \
+  if (hwasan_inited)                                       \
     stack.Unwind(pc, bp, nullptr, common_flags()->fast_unwind_on_fatal)
 
 void HwasanTSDInit();

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff 84cc1865ef9202af39404ff4524a9b13df80cfc1 f112952c5abfe9d4a6e25ebdef203e4c9f1b3818 --extensions h -- compiler-rt/lib/hwasan/hwasan.h

View the diff from clang-format here.

diff --git a/compiler-rt/lib/hwasan/hwasan.h b/compiler-rt/lib/hwasan/hwasan.h
index 1ae463f845..7c9feef0c7 100644
--- a/compiler-rt/lib/hwasan/hwasan.h
+++ b/compiler-rt/lib/hwasan/hwasan.h
@@ -138,17 +138,17 @@ void hwasan_free(void *ptr, StackTrace *stack);
 
 void InstallAtExitHandler();
 
-#define GET_MALLOC_STACK_TRACE                                            \
-  UNINITIALIZED BufferedStackTrace stack;                                 \
-  if (hwasan_inited)                                                      \
-    stack.Unwind(StackTrace::GetCurrentPc(), GET_CURRENT_FRAME(),         \
-                 nullptr, common_flags()->fast_unwind_on_malloc,          \
-                 common_flags()->malloc_context_size)
-
-#define GET_FATAL_STACK_TRACE_PC_BP(pc, bp)              \
-  UNINITIALIZED BufferedStackTrace stack;                \
-  if (hwasan_inited)                                     \
-    stack.Unwind(pc, bp, nullptr, common_flags()->fast_unwind_on_fatal)
+#define GET_MALLOC_STACK_TRACE                                           \
+  UNINITIALIZED BufferedStackTrace stack;                                \
+  if (hwasan_inited)                                                     \
+  stack.Unwind(StackTrace::GetCurrentPc(), GET_CURRENT_FRAME(), nullptr, \
+               common_flags()->fast_unwind_on_malloc,                    \
+               common_flags()->malloc_context_size)
+
+#define GET_FATAL_STACK_TRACE_PC_BP(pc, bp) \
+  UNINITIALIZED BufferedStackTrace stack;   \
+  if (hwasan_inited)                        \
+  stack.Unwind(pc, bp, nullptr, common_flags()->fast_unwind_on_fatal)
 
 void HwasanTSDInit();
 void HwasanTSDThreadInit();