Made checks on client have own macro.

src/mem/alloc.h

@@ -469,7 +469,7 @@ namespace snmalloc
         return;
       }
 
-#  ifndef NDEBUG
+#  ifdef CHECK_CLIENT
       if (size > 64 || address_cast(super) != address_cast(p))
       {
         error("Not deallocating start of an object");
@@ -817,7 +817,7 @@ namespace snmalloc
       {
         Superslab* super = Superslab::get(p);
 
-#ifndef NDEBUG
+#ifdef CHECK_CLIENT
         if (p->target_id() != super->get_allocator()->id())
           error("Detected memory corruption.  Potential use-after-free");
 #endif
@@ -1013,7 +1013,7 @@ namespace snmalloc
 
     void small_dealloc(Superslab* super, void* p, uint8_t sizeclass)
     {
-#ifndef NDEBUG
+#ifdef CHECK_CLIENT
       Slab* slab = Slab::get(p);
       if (!slab->is_start_of_object(super, p))
       {
@@ -1150,7 +1150,7 @@ namespace snmalloc
       stats().sizeclass_dealloc(sizeclass);
       bool was_full = slab->dealloc(p, large_allocator.memory_provider);
 
-#ifndef NDEBUG
+#ifdef CHECK_CLIENT
       if (!is_multiple_of_sizeclass(
             sizeclass_to_size(sizeclass),
             address_cast(slab) + SUPERSLAB_SIZE - address_cast(p)))

src/mem/allocconfig.h

@@ -4,6 +4,12 @@
 
 namespace snmalloc
 {
+// The CHECK_CLIENT macro is used to turn on minimal checking of the client
+// calling the API correctly.
+#if !defined(NDEBUG) && !defined(CHECK_CLIENT)
+#  define CHECK_CLIENT
+#endif
+
   // 0 intermediate bits results in power of 2 small allocs. 1 intermediate
   // bit gives additional sizeclasses at the midpoint between each power of 2.
   // 2 intermediate bits gives 3 intermediate sizeclasses, etc.

src/mem/metaslab.h

@@ -99,7 +99,7 @@ namespace snmalloc
     /// simple corruptions.
     static void store_next(void* p, uint16_t head)
     {
-#ifdef NDEBUG
+#ifndef CHECK_CLIENT
       *static_cast<size_t*>(p) = head;
 #else
       *static_cast<size_t*>(p) =
@@ -112,7 +112,7 @@ namespace snmalloc
     static uint16_t follow_next(void* node)
     {
       size_t next = *static_cast<size_t*>(node);
-#ifndef NDEBUG
+#ifdef CHECK_CLIENT
       if (((next ^ POISON) ^ (next << (bits::BITS - 16))) > 0xFFFF)
         error("Detected memory corruption.  Use-after-free.");
 #endif

src/mem/slab.h

@@ -101,7 +101,7 @@ namespace snmalloc
 
       bool was_full = meta.is_full();
 
-#ifndef NDEBUG
+#ifdef CHECK_CLIENT
       if (meta.is_unused())
         error("Detected potential double free.");
 #endif