From 85cf5dd097226465334821274596b7c7b7ed80a4 Mon Sep 17 00:00:00 2001
From: theodus <theodusbutler@gmail.com>
Date: Sat, 2 Feb 2019 14:47:06 -0500
Subject: [PATCH] Avoid unnecessary allocation from realloc

---
 src/mem/slab.h         | 2 +-
 src/override/malloc.cc | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/mem/slab.h b/src/mem/slab.h
index 6387dc6..67f9712 100644
--- a/src/mem/slab.h
+++ b/src/mem/slab.h
@@ -71,7 +71,7 @@ namespace snmalloc
 
       meta.debug_slab_invariant(is_short(), this);
 
-      if (zero_mem == YesZero)
+      if constexpr (zero_mem == YesZero)
       {
         if (rsize < PAGE_ALIGNED_SIZE)
           memory_provider.zero(p, rsize);
diff --git a/src/override/malloc.cc b/src/override/malloc.cc
index 5e3bf1f..7190f99 100644
--- a/src/override/malloc.cc
+++ b/src/override/malloc.cc
@@ -80,13 +80,14 @@ extern "C"
         "Calling realloc on pointer that is not to the start of an allocation");
     }
 #endif
+    if (size <= SNMALLOC_NAME_MANGLE(malloc_usable_size)(ptr))
+      return ptr;
+
     void* p = SNMALLOC_NAME_MANGLE(malloc)(size);
-    if (p)
+    if (p != nullptr)
     {
       assert(p == Alloc::external_pointer<Start>(p));
-      size_t sz =
-        (std::min)(size, SNMALLOC_NAME_MANGLE(malloc_usable_size)(ptr));
-      memcpy(p, ptr, sz);
+      memcpy(p, ptr, size);
       SNMALLOC_NAME_MANGLE(free)(ptr);
     }
     return p;