Downgrade some casts

Do a quick sweep through the codebase to eliminate some reinterpret_cast<>s
where less fire power would do just fine.

src/backend/pagemap.h

@@ -130,7 +130,7 @@ namespace snmalloc
 
       // Put pagemap at start of range.
       // TODO CHERI capability bound here!
-      body = reinterpret_cast<T*>(b);
+      body = static_cast<T*>(b);
       body_opt = body;
       // Advance by size of pagemap.
       // Note that base needs to be aligned to GRANULARITY for the rest of the
@@ -176,8 +176,7 @@ namespace snmalloc
       // Begin pagemap at random offset within the additionally allocated space.
       static_assert(bits::is_pow2(sizeof(T)), "Next line assumes this.");
       size_t offset = get_entropy64<PAL>() & (additional_size - sizeof(T));
-      auto new_body =
-        reinterpret_cast<T*>(pointer_offset(new_body_untyped, offset));
+      auto new_body = pointer_offset<T>(new_body_untyped, offset);
 
       if constexpr (pal_supports<LazyCommit, PAL>)
       {
@@ -191,7 +190,7 @@ namespace snmalloc
           start_page, pointer_diff(start_page, end_page));
       }
 #else
-      auto new_body = reinterpret_cast<T*>(new_body_untyped);
+      auto new_body = static_cast<T*>(new_body_untyped);
 #endif
       // Ensure bottom page is committed
       // ASSUME: new memory is zeroed.

src/test/func/malloc/malloc.cc

@@ -88,16 +88,12 @@ void check_result(size_t size, size_t align, void* p, int err, bool null)
       expected_size);
     failed = true;
   }
-  if (
-    (static_cast<size_t>(reinterpret_cast<uintptr_t>(p) % align) != 0) &&
-    (size != 0))
+  if (((address_cast(p) % align) != 0) && (size != 0))
   {
     INFO("Address is {}, but required to be aligned to {}.\n", p, align);
     failed = true;
   }
-  if (
-    static_cast<size_t>(
-      reinterpret_cast<uintptr_t>(p) % natural_alignment(size)) != 0)
+  if ((address_cast(p) % natural_alignment(size)) != 0)
   {
     INFO(
       "Address is {}, but should have natural alignment to {}.\n",

src/test/func/memcpy/func-memcpy.cc

@@ -69,8 +69,8 @@ extern "C" void abort()
 void check_size(size_t size)
 {
   START_TEST("checking {}-byte memcpy", size);
-  auto* s = reinterpret_cast<unsigned char*>(my_malloc(size + 1));
-  auto* d = reinterpret_cast<unsigned char*>(my_malloc(size + 1));
+  auto* s = static_cast<unsigned char*>(my_malloc(size + 1));
+  auto* d = static_cast<unsigned char*>(my_malloc(size + 1));
   d[size] = 0;
   s[size] = 255;
   for (size_t start = 0; start < size; start++)
@@ -115,8 +115,8 @@ void check_bounds(size_t size, size_t out_of_bounds)
 {
   START_TEST(
     "memcpy bounds, size {}, {} bytes out of bounds", size, out_of_bounds);
-  auto* s = reinterpret_cast<unsigned char*>(my_malloc(size));
-  auto* d = reinterpret_cast<unsigned char*>(my_malloc(size));
+  auto* s = static_cast<unsigned char*>(my_malloc(size));
+  auto* d = static_cast<unsigned char*>(my_malloc(size));
   for (size_t i = 0; i < size; ++i)
   {
     s[i] = static_cast<unsigned char>(i);

src/test/perf/memcpy/memcpy.cc

@@ -30,7 +30,7 @@ void shape(size_t size)
     // size / alignment) * alignment;
     Shape s;
     s.object = ThreadAlloc::get().alloc(rsize);
-    s.dst = reinterpret_cast<unsigned char*>(s.object) + offset;
+    s.dst = static_cast<unsigned char*>(s.object) + offset;
     // Bring into cache the destination of the copy.
     memset(s.dst, 0xFF, size);
     allocs.push_back(s);
@@ -51,7 +51,7 @@ void test_memcpy(size_t size, void* src, Memcpy mc)
 {
   for (auto& s : allocs)
   {
-    auto* dst = reinterpret_cast<unsigned char*>(s.dst);
+    auto* dst = static_cast<unsigned char*>(s.dst);
     mc(dst, src, size);
   }
 }