diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2bfc4ecc7..61359b76c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -76,11 +76,18 @@ subdirlist(TEST_CATEGORIES ${TESTDIR})
 foreach(SUPER_SLAB_SIZE 1;16)
   foreach(TEST_CATEGORY ${TEST_CATEGORIES})
     subdirlist(TESTS ${TESTDIR}/${TEST_CATEGORY})
+    if(MSVC)
+      list(REMOVE_ITEM TESTS "malloc")
+    endif()
     foreach(TEST ${TESTS})
       unset(SRC)
       aux_source_directory(${TESTDIR}/${TEST_CATEGORY}/${TEST} SRC)
       set(TESTNAME "${TEST_CATEGORY}-${TEST}-${SUPER_SLAB_SIZE}")
-      add_executable(${TESTNAME} ${SRC} src/override/new.cc)
+      if(${TEST} STREQUAL "malloc")
+        add_executable(${TESTNAME} ${SRC} src/override/malloc.cc)
+      else()
+        add_executable(${TESTNAME} ${SRC} src/override/new.cc)
+      endif()
       if (${SUPER_SLAB_SIZE} EQUAL 1)
         target_compile_definitions(${TESTNAME} PRIVATE IS_ADDRESS_SPACE_CONSTRAINED)
       endif()
diff --git a/src/override/malloc.cc b/src/override/malloc.cc
index 218191e58..7c704d46c 100644
--- a/src/override/malloc.cc
+++ b/src/override/malloc.cc
@@ -43,7 +43,7 @@ extern "C"
     if (overflow)
     {
       errno = ENOMEM;
-      return 0;
+      return nullptr;
     }
     // Include size 0 in the first sizeclass.
     sz = ((sz - 1) >> (bits::BITS - 1)) + sz;
@@ -135,7 +135,8 @@ extern "C"
       return nullptr;
     }
 
-    uint8_t sc = size_to_sizeclass((std::max)(size, alignment));
+    size = (std::max)(size, alignment);
+    uint8_t sc = size_to_sizeclass(size);
     if (sc >= NUM_SIZECLASSES)
     {
       // large allocs are 16M aligned.
@@ -149,8 +150,7 @@ extern "C"
         return SNMALLOC_NAME_MANGLE(aligned_alloc)(alignment, size);
       }
     }
-    assert(false);
-    return nullptr;
+    return SNMALLOC_NAME_MANGLE(malloc)(SUPERSLAB_SIZE);
   }
 
   SNMALLOC_EXPORT int SNMALLOC_NAME_MANGLE(posix_memalign)(
diff --git a/src/pal/pal_free_bsd_kernel.h b/src/pal/pal_free_bsd_kernel.h
index 1ae5d2c5d..184e854ee 100644
--- a/src/pal/pal_free_bsd_kernel.h
+++ b/src/pal/pal_free_bsd_kernel.h
@@ -36,7 +36,7 @@ namespace snmalloc
       kmem_unback(kernel_object, addr, size);
     }
 
-    /// Notify platform that we will not be using these pages
+    /// Notify platform that we will be using these pages
     template<ZeroMem zero_mem>
     void notify_using(void* p, size_t size)
     {
diff --git a/src/pal/pal_freebsd.h b/src/pal/pal_freebsd.h
index 90a2f5b7a..4b1e856fe 100644
--- a/src/pal/pal_freebsd.h
+++ b/src/pal/pal_freebsd.h
@@ -27,7 +27,7 @@ namespace snmalloc
       madvise(p, size, MADV_FREE);
     }
 
-    /// Notify platform that we will not be using these pages
+    /// Notify platform that we will be using these pages
     template<ZeroMem zero_mem>
     void notify_using(void* p, size_t size) noexcept
     {
diff --git a/src/pal/pal_linux.h b/src/pal/pal_linux.h
index 711d77428..fb0605807 100644
--- a/src/pal/pal_linux.h
+++ b/src/pal/pal_linux.h
@@ -29,7 +29,7 @@ namespace snmalloc
       UNUSED(size);
     }
 
-    /// Notify platform that we will not be using these pages
+    /// Notify platform that we will be using these pages
     template<ZeroMem zero_mem>
     void notify_using(void* p, size_t size) noexcept
     {
diff --git a/src/pal/pal_windows.h b/src/pal/pal_windows.h
index 7fcd00ec1..82b6b6cf1 100644
--- a/src/pal/pal_windows.h
+++ b/src/pal/pal_windows.h
@@ -30,7 +30,7 @@ namespace snmalloc
         error("VirtualFree failed");
     }
 
-    /// Notify platform that we will not be using these pages
+    /// Notify platform that we will be using these pages
     template<ZeroMem zero_mem>
     void notify_using(void* p, size_t size) noexcept
     {
@@ -108,4 +108,4 @@ namespace snmalloc
     }
   };
 }
-#endif
\ No newline at end of file
+#endif
diff --git a/src/test/func/malloc/malloc.cc b/src/test/func/malloc/malloc.cc
new file mode 100644
index 000000000..7cb02a384
--- /dev/null
+++ b/src/test/func/malloc/malloc.cc
@@ -0,0 +1,118 @@
+#include <cerrno>
+#include <malloc.h>
+#include <snmalloc.h>
+
+using namespace snmalloc;
+
+void check_result(size_t size, size_t align, void* p, int err, bool null)
+{
+  if (errno != err)
+    abort();
+
+  if (null)
+  {
+    if (p != nullptr)
+      abort();
+  }
+  else
+  {
+    if (malloc_usable_size(p) < size)
+      abort();
+
+    if (((uintptr_t)p % align) != 0)
+      abort();
+
+    free(p);
+  }
+}
+
+void test_calloc(size_t nmemb, size_t size, int err, bool null)
+{
+  fprintf(stderr, "calloc(%d, %d)\n", (int)nmemb, (int)size);
+  errno = 0;
+  void* p = calloc(nmemb, size);
+
+  if ((p != nullptr) && (errno == 0))
+  {
+    for (size_t i = 0; i < (size * nmemb); i++)
+    {
+      if (((uint8_t*)p)[i] != 0)
+        abort();
+    }
+  }
+  check_result(nmemb * size, 1, p, err, null);
+}
+
+void test_realloc(void* p, size_t size, int err, bool null)
+{
+  fprintf(stderr, "realloc(%p(%d), %d)\n", p, int(size), (int)size);
+  errno = 0;
+  p = realloc(p, size);
+  check_result(size, 1, p, err, null);
+}
+
+void test_posix_memalign(size_t size, size_t align, int err, bool null)
+{
+  fprintf(stderr, "posix_memalign(&p, %d, %d)\n", (int)align, (int)size);
+  void* p = nullptr;
+  errno = posix_memalign(&p, align, size);
+  check_result(size, align, p, err, null);
+}
+
+void test_memalign(size_t size, size_t align, int err, bool null)
+{
+  fprintf(stderr, "memalign(%d, %d)\n", (int)align, (int)size);
+  errno = 0;
+  void* p = memalign(align, size);
+  check_result(size, align, p, err, null);
+}
+
+int main(int argc, char** argv)
+{
+  UNUSED(argc);
+  UNUSED(argv);
+
+  constexpr int SUCCESS = 0;
+
+  test_calloc(0, 0, SUCCESS, false);
+
+  for (uint8_t sc = 0; sc < NUM_SIZECLASSES; sc++)
+  {
+    const size_t size = sizeclass_to_size(sc);
+
+    bool overflow = false;
+    for (size_t n = 1; bits::umul(size, n, overflow) <= SUPERSLAB_SIZE; n *= 5)
+    {
+      if (overflow)
+        break;
+
+      test_calloc(n, size, SUCCESS, false);
+      test_calloc(n, 0, SUCCESS, false);
+    }
+    test_calloc(0, size, SUCCESS, false);
+
+    test_realloc(malloc(size), size, SUCCESS, false);
+    test_realloc(malloc(size), 0, SUCCESS, true);
+    test_realloc(nullptr, size, SUCCESS, false);
+    test_realloc(malloc(size), (size_t)-1, ENOMEM, true);
+  }
+
+  test_posix_memalign(0, 0, EINVAL, true);
+  test_posix_memalign((size_t)-1, 0, EINVAL, true);
+
+  for (size_t align = sizeof(size_t); align <= SUPERSLAB_SIZE; align <<= 1)
+  {
+    for (uint8_t sc = 0; sc < NUM_SIZECLASSES; sc++)
+    {
+      const size_t size = sizeclass_to_size(sc);
+      test_posix_memalign(size, align, SUCCESS, false);
+      test_posix_memalign(size, 0, EINVAL, true);
+      test_memalign(size, align, SUCCESS, false);
+    }
+    test_posix_memalign(0, align, SUCCESS, false);
+    test_posix_memalign((size_t)-1, align, ENOMEM, true);
+    test_posix_memalign(0, align + 1, EINVAL, true);
+  }
+
+  return 0;
+}
diff --git a/src/test/func/rounding/rounding.cc b/src/test/func/rounding/rounding.cc
index e15cfd6fe..8c3a9e8b7 100644
--- a/src/test/func/rounding/rounding.cc
+++ b/src/test/func/rounding/rounding.cc
@@ -1,7 +1,4 @@
 #include <snmalloc.h>
-#include <test/opt.h>
-#include <test/xoroshiro.h>
-#include <unordered_set>
 
 using namespace snmalloc;