Address Matt's review comments.

src/mem/alloc.h

@@ -101,7 +101,7 @@ namespace snmalloc
 
   public:
     /**
-     * Construtor.  Accesses the pagemap via the C ABI accessor and casts it to
+     * Constructor.  Accesses the pagemap via the C ABI accessor and casts it to
      * the expected type, failing in cases of ABI mismatch.
      */
     ExternalGlobalPagemap()

src/mem/pagemap.h

@@ -30,6 +30,10 @@ namespace snmalloc
      * hierarchical structure.
      */
     bool is_flat_pagemap;
+    /**
+     * Number of bytes in a pointer.
+     */
+    uint8_t sizeof_pointer;
     /**
      * The number of bits of the address used to index into the pagemap.
      */
@@ -202,7 +206,7 @@ namespace snmalloc
      * The pagemap configuration describing this instantiation of the template.
      */
     static constexpr PagemapConfig config = {
-      1, false, GRANULARITY_BITS, sizeof(T)};
+      1, false, sizeof(void*), GRANULARITY_BITS, sizeof(T)};
 
     /**
      * Cast a `void*` to a pointer to this template instantiation, given a
@@ -216,6 +220,7 @@ namespace snmalloc
     {
       if (
         (c->version != 1) || (c->is_flat_pagemap) ||
+        (c->sizeof_pointer == sizeof(void*)) ||
         (c->pagemap_bits != GRANULARITY_BITS) ||
         (c->size_of_entry != sizeof(T)) || (!std::is_integral_v<T>))
       {
@@ -306,7 +311,7 @@ namespace snmalloc
      * The pagemap configuration describing this instantiation of the template.
      */
     static constexpr PagemapConfig config = {
-      1, true, GRANULARITY_BITS, sizeof(T)};
+      1, true, sizeof(void*), GRANULARITY_BITS, sizeof(T)};
 
     /**
      * Cast a `void*` to a pointer to this template instantiation, given a
@@ -320,6 +325,7 @@ namespace snmalloc
     {
       if (
         (c->version != 1) || (!c->is_flat_pagemap) ||
+        (c->sizeof_pointer == sizeof(void*)) ||
         (c->pagemap_bits != GRANULARITY_BITS) ||
         (c->size_of_entry != sizeof(T)) || (!std::is_integral_v<T>))
       {

src/test/func/two_alloc_types/main.cc

@@ -48,8 +48,9 @@ int main()
   std::cout << "Allocated region " << oe_base << " - " << oe_end << std::endl;
 
   // Call these functions to trigger asserts if the cast-to-self doesn't work.
-  enclave_snmalloc_pagemap_global_get(nullptr);
-  host_snmalloc_pagemap_global_get(nullptr);
+  PagemapConfig *c;
+  enclave_snmalloc_pagemap_global_get(&c);
+  host_snmalloc_pagemap_global_get(&c);
 
   auto a = host_malloc(128);
   auto b = enclave_malloc(128);