GTTF: cherry-pick memalign/realloc mismatch debug code

third_party/tcmalloc/chromium/src/debugallocation.cc

Index: third_party/tcmalloc/chromium/src/debugallocation.cc
diff --git a/third_party/tcmalloc/chromium/src/debugallocation.cc b/third_party/tcmalloc/chromium/src/debugallocation.cc
index 74b802609f4639e5a024505a3882f0b94ed8079b..cccaf982b3115451b97e1e9bcbbae4e2c2216e74 100644
--- a/third_party/tcmalloc/chromium/src/debugallocation.cc
+++ b/third_party/tcmalloc/chromium/src/debugallocation.cc
@@ -743,6 +743,17 @@ class MallocBlock {
     return FromRawPointer(const_cast<void*>(p));
   }
 
+  // Return whether p points to memory returned by memalign.
+  // Requires that p be non-zero and has been checked for sanity with
+  // FromRawPointer().
+  static bool IsMemaligned(const void* p) {
+    const MallocBlock* mb = reinterpret_cast<const MallocBlock*>(
+        reinterpret_cast<const char*>(p) - MallocBlock::data_offset());
+    // If the offset is non-zero, the block was allocated by memalign
+    // (see FromRawPointer above).
+    return mb->offset_ != 0;

[jar (doing other things), 2013/01/16 00:59:32]

Why is this safe to call if you don't know if this is really a malloc block?

[Paweł Hajdan Jr., 2013/01/16 01:05:09]

1. Note this has been reviewed and committed Google-side. It's just a backport.
2. See the "Requires that... has been checked for sanity" comment, and we
actually call Check before calling IsMemaligned.

+  }
+
   void Check(int type) const {
     alloc_map_lock_.Lock();
     CheckLocked(type);
@@ -1190,13 +1201,18 @@ extern "C" PERFTOOLS_DLL_DECL void* tc_realloc(void* ptr, size_t size) __THROW {
     MallocHook::InvokeNewHook(ptr, size);
     return ptr;
   }
+  MallocBlock* old = MallocBlock::FromRawPointer(ptr);
+  old->Check(MallocBlock::kMallocType);
+  if (MallocBlock::IsMemaligned(ptr)) {
+    RAW_LOG(FATAL, "realloc/memalign mismatch at %p: "
+            "non-NULL pointers passed to realloc must be obtained "
+            "from malloc, calloc, or realloc", ptr);
+  }
   if (size == 0) {
     MallocHook::InvokeDeleteHook(ptr);
     DebugDeallocate(ptr, MallocBlock::kMallocType);
     return NULL;
   }
-  MallocBlock* old = MallocBlock::FromRawPointer(ptr);
-  old->Check(MallocBlock::kMallocType);
   MallocBlock* p = MallocBlock::Allocate(size, MallocBlock::kMallocType);
 
   // If realloc fails we are to leave the old block untouched and