[NOT TO COMMIT!] Merge Chromium-specific changes in tcmalloc thru. the original gperftools r136.

third_party/tcmalloc/chromium/src/system-alloc.cc

Index: third_party/tcmalloc/chromium/src/system-alloc.cc
diff --git a/third_party/tcmalloc/chromium/src/system-alloc.cc b/third_party/tcmalloc/chromium/src/system-alloc.cc
index ea718b3990f60531b267410d1b075aad4f3a190c..d11a6021335454421484c2533be3286e77ea612a 100644
--- a/third_party/tcmalloc/chromium/src/system-alloc.cc
+++ b/third_party/tcmalloc/chromium/src/system-alloc.cc
@@ -114,8 +114,7 @@ union MemoryAligner {
 
 static SpinLock spinlock(SpinLock::LINKER_INITIALIZED);
 
-#if defined(HAVE_MMAP) || defined(MADV_FREE)
-// Page size is initialized on demand (only needed for mmap-based allocators)
+#ifdef HAVE_GETPAGESIZE
 static size_t pagesize = 0;
 #endif
 
@@ -195,7 +194,6 @@ static const char mmap_name[] = "MmapSysAllocator";
 void* SbrkSysAllocator::Alloc(size_t size, size_t *actual_size,
                               size_t alignment) {
 #ifndef HAVE_SBRK
-  failed_ = true;
   return NULL;
 #else
   // Check if we should use sbrk allocation.
@@ -210,7 +208,7 @@ void* SbrkSysAllocator::Alloc(size_t size, size_t *actual_size,
 
   // sbrk will release memory if passed a negative number, so we do
   // a strict check here
-  if (static_cast<ptrdiff_t>(size + alignment) < 0) return NULL;
+  if (static_cast<std::ptrdiff_t>(size + alignment) < 0) return NULL;
 
   // This doesn't overflow because TCMalloc_SystemAlloc has already
   // tested for overflow at the alignment boundary.
@@ -267,7 +265,6 @@ void* SbrkSysAllocator::Alloc(size_t size, size_t *actual_size,
 void* MmapSysAllocator::Alloc(size_t size, size_t *actual_size,
                               size_t alignment) {
 #ifndef HAVE_MMAP
-  failed_ = true;
   return NULL;
 #else
   // Check if we should use mmap allocation.
@@ -336,7 +333,6 @@ void* MmapSysAllocator::Alloc(size_t size, size_t *actual_size,
 void* DevMemSysAllocator::Alloc(size_t size, size_t *actual_size,
                                 size_t alignment) {
 #ifndef HAVE_MMAP
-  failed_ = true;
   return NULL;
 #else
   static bool initialized = false;
@@ -493,6 +489,21 @@ void* TCMalloc_SystemAlloc(size_t size, size_t *actual_size,
   return result;
 }
 
+size_t TCMalloc_SystemAddGuard(void* start, size_t size) {
+#ifdef HAVE_GETPAGESIZE
+  if (pagesize == 0)
+    pagesize = getpagesize();
+
+  if (size < pagesize || (reinterpret_cast<size_t>(start) % pagesize) != 0)
+    return 0;
+
+  if (!mprotect(start, pagesize, PROT_NONE))
+    return pagesize;
+#endif
+
+  return 0;
+}
+
 void TCMalloc_SystemRelease(void* start, size_t length) {
 #ifdef MADV_FREE
   if (FLAGS_malloc_devmem_start) {
@@ -528,3 +539,9 @@ void TCMalloc_SystemRelease(void* start, size_t length) {
   }
 #endif
 }
+
+void TCMalloc_SystemCommit(void* start, size_t length) {
+  // Nothing to do here.  TCMalloc_SystemRelease does not alter pages
+  // such that they need to be re-committed before they can be used by the
+  // application.
+}