unbreak calloc memsetting extra memory in emergency malloc mode

2 files changed, 23 insertions, 2 deletions

diff --git a/src/tcmalloc.cc b/src/tcmalloc.cc
index c51a351..60f5e9b 100644
--- a/src/tcmalloc.cc
+++ b/src/tcmalloc.cc
@@ -1510,7 +1510,19 @@ ALWAYS_INLINE void* do_calloc(size_t n, size_t elem_size) {
 
   void* result = do_malloc_or_cpp_alloc(size);
   if (result != NULL) {
-    memset(result, 0, tc_nallocx(size, 0));
+    size_t total_size = size;
+    if (!tcmalloc::IsEmergencyPtr(result)) {
+      // On windows we support recalloc (which was apparently
+      // originally introduced in Irix). In order for recalloc to work
+      // we need to zero-out not just the size we were asked for, but
+      // entire usable size. See also
+      // https://github.com/gperftools/gperftools/pull/994.
+      //
+      // But we can do it only when not dealing with emergency
+      // malloc-ed memory.
+      total_size = tc_nallocx(size, 0);
+    }
+    memset(result, 0, total_size);
   }
   return result;
 }
diff --git a/src/tests/tcmalloc_unittest.cc b/src/tests/tcmalloc_unittest.cc
index 85fde79..c03315e 100644
--- a/src/tests/tcmalloc_unittest.cc
+++ b/src/tests/tcmalloc_unittest.cc
@@ -1604,19 +1604,26 @@ TEST(TCMallocTest, EmergencyMallocNoHook) {
   void* p1 = noopt(tc_malloc)(32);
   void* p2 = nullptr;
   void* p3 = nullptr;
+  void* p4 = nullptr;
 
   portal->WithEmergencyMallocEnabled([&] () {
     p2 = noopt(malloc)(32);
-    p3 = tc_calloc(4096, 1024);
+    for (int i = 11; i < 999; i++) {
+      free(p3);
+      p3 = tc_calloc(1, i);
+    }
+    p4 = tc_calloc(4096, 1024);
   });
 
   ASSERT_NE(p2, nullptr);
   ASSERT_NE(p3, nullptr);
+  ASSERT_NE(p4, nullptr);
 
   // Emergency malloc doesn't return pointers recognized by MallocExtension
   ASSERT_EQ(MallocExtension::instance()->GetOwnership(p1), MallocExtension::kOwned);
   ASSERT_EQ(MallocExtension::instance()->GetOwnership(p2), MallocExtension::kNotOwned);
   ASSERT_EQ(MallocExtension::instance()->GetOwnership(p3), MallocExtension::kNotOwned);
+  ASSERT_EQ(MallocExtension::instance()->GetOwnership(p4), MallocExtension::kNotOwned);
 
   SetNewHook();
   SetDeleteHook();
@@ -1627,6 +1634,8 @@ TEST(TCMallocTest, EmergencyMallocNoHook) {
 
   // Emergency malloc automagically does the right thing for free()
   // calls and doesn't invoke hooks.
+  tc_free(p4);
+  tc_free(p3);
   tc_free(p2);
   ASSERT_EQ(g_DeleteHook_calls, 0);