Make snmalloc build on Windows with Clang

Fixes a few places where Clang complains about Windows specific code,
and also uses macros supported by Clang on Windows.  A few places
separating platform and compiler specific code, as MSVC and WIN32 were
used interchangably previously.

src/ds/aba.h

@@ -97,7 +97,7 @@ namespace snmalloc
 #  if defined(_MSC_VER) && defined(SNMALLOC_VA_BITS_64)
       return _InterlockedCompareExchange128(
         (volatile __int64*)&linked,
-        expect.aba + 1,
+        (__int64)(expect.aba + (uintptr_t)1),
         (__int64)value,
         (__int64*)&expect);
 #  else

src/ds/bits.h

@@ -138,13 +138,16 @@ namespace snmalloc
 
     inline size_t ctz(size_t x)
     {
-#if defined(_MSC_VER)
+#if __has_builtin(__builtin_ctzl)
+      return static_cast<size_t>(__builtin_ctzl(x));
+#elif defined(_MSC_VER)
 #  ifdef SNMALLOC_VA_BITS_64
       return _tzcnt_u64(x);
 #  else
       return _tzcnt_u32((uint32_t)x);
 #  endif
 #else
+      // Probably GCC at this point.
       return static_cast<size_t>(__builtin_ctzl(x));
 #endif
     }

src/ds/defines.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) && !defined(__clang__)
 #  define ALWAYSINLINE __forceinline
 #  define NOINLINE __declspec(noinline)
 #  define likely(x) !!(x)

src/mem/remoteallocator.h

@@ -18,8 +18,8 @@ namespace snmalloc
     using alloc_id_t = size_t;
     union
     {
-      std::atomic<Remote*> next;
       Remote* non_atomic_next;
+      std::atomic<Remote*> next = nullptr;
     };
 
     alloc_id_t allocator_id;

src/pal/pal_windows.h

@@ -200,11 +200,14 @@ namespace snmalloc
       // If we're on Windows 10 or newer, we can use the VirtualAlloc2
       // function.  The FromApp variant is useable by UWP applications and
       // cannot allocate executable memory.
-      MEM_ADDRESS_REQUIREMENTS addressReqs = {0};
-      MEM_EXTENDED_PARAMETER param = {0};
-      addressReqs.Alignment = align;
-      param.Type = MemExtendedParameterAddressRequirements;
+      MEM_ADDRESS_REQUIREMENTS addressReqs = {NULL, NULL, align};
+
+      MEM_EXTENDED_PARAMETER param = {
+        {MemExtendedParameterAddressRequirements, 0}, {0}};
+      // Separate assignment as MSVC doesn't support .Pointer in the
+      // initialisation list.
       param.Pointer = &addressReqs;
+
       void* ret = VirtualAlloc2FromApp(
         nullptr, nullptr, *size, flags, PAGE_READWRITE, &param, 1);
       if (ret == nullptr)

src/test/setup.h

@@ -25,7 +25,7 @@ void print_stack_trace()
   {
     // SymInitialize failed
     error = GetLastError();
-    printf("SymInitialize returned error : %d\n", error);
+    printf("SymInitialize returned error : %lu\n", error);
     return;
   }