1 files changed, 44 insertions, 3 deletions

diff --git a/src/google/malloc_extension.h b/src/google/malloc_extension.h
index a2e956e..0e15c04 100644
--- a/src/google/malloc_extension.h
+++ b/src/google/malloc_extension.h
@@ -70,6 +70,22 @@ namespace base {
 struct MallocRange;
 }
 
+// Interface to a pluggable system allocator.
+class SysAllocator {
+ public:
+  SysAllocator() {
+  }
+  virtual ~SysAllocator();
+
+  // Allocates "size"-byte of memory from system aligned with "alignment".
+  // Returns NULL if failed. Otherwise, the returned pointer p up to and
+  // including (p + actual_size -1) have been allocated.
+  virtual void* Alloc(size_t size, size_t *actual_size, size_t alignment) = 0;
+
+  // Notification that command-line flags have been initialized.
+  virtual void FlagsInitialized() = 0;
+};
+
 // The default implementations of the following routines do nothing.
 // All implementations should be thread-safe; the current one
 // (TCMallocImplementation) is.
@@ -102,7 +118,9 @@ class PERFTOOLS_DLL_DECL MallocExtension {
   // Outputs to "writer" a sample of live objects and the stack traces
   // that allocated these objects.  The format of the returned output
   // is equivalent to the output of the heap profiler and can
-  // therefore be passed to "pprof".
+  // therefore be passed to "pprof". This function is equivalent to
+  // ReadStackTraces. The main difference is that this function returns
+  // serialized data appropriately formatted for use by the pprof tool.
   // NOTE: by default, tcmalloc does not do any heap sampling, and this
   //       function will always return an empty sample.  To get useful
   //       data from GetHeapSample, you must also set the environment
@@ -112,7 +130,10 @@ class PERFTOOLS_DLL_DECL MallocExtension {
   // Outputs to "writer" the stack traces that caused growth in the
   // address space size.  The format of the returned output is
   // equivalent to the output of the heap profiler and can therefore
-  // be passed to "pprof".  (This does not depend on, or require,
+  // be passed to "pprof". This function is equivalent to
+  // ReadHeapGrowthStackTraces. The main difference is that this function
+  // returns serialized data appropriately formatted for use by the
+  // pprof tool.  (This does not depend on, or require,
   // TCMALLOC_SAMPLE_PARAMETER.)
   virtual void GetHeapGrowthStacks(MallocExtensionWriter* writer);
 
@@ -201,6 +222,27 @@ class PERFTOOLS_DLL_DECL MallocExtension {
   // Most malloc implementations ignore this routine.
   virtual void MarkThreadBusy();
 
+  // Gets the system allocator used by the malloc extension instance. Returns
+  // NULL for malloc implementations that do not support pluggable system
+  // allocators.
+  virtual SysAllocator* GetSystemAllocator();
+
+  // Sets the system allocator to the specified.
+  //
+  // Users could register their own system allocators for malloc implementation
+  // that supports pluggable system allocators, such as TCMalloc, by doing:
+  //   alloc = new MyOwnSysAllocator();
+  //   MallocExtension::instance()->SetSystemAllocator(alloc);
+  // It's up to users whether to fall back (recommended) to the default
+  // system allocator (use GetSystemAllocator() above) or not. The caller is
+  // responsible to any necessary locking.
+  // See tcmalloc/system-alloc.h for the interface and
+  //     tcmalloc/memfs_malloc.cc for the examples.
+  //
+  // It's a no-op for malloc implementations that do not support pluggable
+  // system allocators.
+  virtual void SetSystemAllocator(SysAllocator *a);
+
   // Try to release num_bytes of free memory back to the operating
   // system for reuse.  Use this extension with caution -- to get this
   // memory back may require faulting pages back in by the OS, and
@@ -289,7 +331,6 @@ class PERFTOOLS_DLL_DECL MallocExtension {
   // "tcmalloc.thread" - tcmalloc's per-thread caches. Never unmapped.
   virtual void GetFreeListSizes(std::vector<FreeListInfo>* v);
 
- protected:
   // Get a list of stack traces of sampled allocation points.  Returns
   // a pointer to a "new[]-ed" result array, and stores the sample
   // period in "sample_period".