Expose reserve_at_least in all Pals

docs/PORTING.md

@@ -49,9 +49,10 @@ template<bool committed>
 static void* reserve_aligned(size_t size) noexcept;
 static std::pair<void*, size_t> reserve_at_least(size_t size) noexcept;
 ```
-Only one of these needs to be implemented, depending on whether the underlying
+All platforms should provide `reserve_at_least` and can optionally provide
-system can provide strongly aligned memory regions.
+`reserve_aligned` if the underlying system can provide strongly aligned 
-If the system guarantees only page alignment, implement the second. The Pal is 
+memory regions.
+If the system guarantees only page alignment, implement only the second. The Pal is 
 free to overallocate based on the platform's desire and snmalloc
 will find suitably aligned blocks inside the region.  `reserve_at_least` should 
 not commit memory as snmalloc will commit the range of memory it requires of what 

src/pal/pal_bsd_aligned.h

@@ -50,17 +50,5 @@ namespace snmalloc
 
       return p;
     }
-
-    /**
-     * Explicitly deleted method for returning non-aligned memory.  This causes
-     * incorrect use of `constexpr if` to fail on platforms with aligned
-     * allocation.  Without this, this PAL and its subclasses exported both
-     * allocation functions and so callers would type-check if they called
-     * either in `constexpr if` branches and then fail on platforms such as
-     * Linux or Windows, which expose only unaligned or aligned allocations,
-     * respectively.
-     */
-    static std::pair<void*, size_t>
-    reserve_at_least(size_t size) noexcept = delete;
   };
 } // namespace snmalloc

src/pal/pal_windows.h

@@ -152,38 +152,7 @@ namespace snmalloc
         ::memset(p, 0, size);
     }
 
-#  ifdef USE_SYSTEMATIC_TESTING
+#  ifdef PLATFORM_HAS_VIRTUALALLOC2
-    static size_t& systematic_bump_ptr()
-    {
-      static size_t bump_ptr = (size_t)0x4000'0000'0000;
-      return bump_ptr;
-    }
-
-    static std::pair<void*, size_t> reserve_at_least(size_t size) noexcept
-    {
-      // Magic number for over-allocating chosen by the Pal
-      // These should be further refined based on experiments.
-      constexpr size_t min_size =
-        bits::is64() ? bits::one_at_bit(32) : bits::one_at_bit(28);
-      auto size_request = bits::max(size, min_size);
-
-      DWORD flags = MEM_RESERVE;
-
-      size_t retries = 1000;
-      void* p;
-
-      do
-      {
-        p = VirtualAlloc(
-          (void*)systematic_bump_ptr(), size_request, flags, PAGE_READWRITE);
-
-        systematic_bump_ptr() += size_request;
-        retries--;
-      } while (p == nullptr && retries > 0);
-
-      return {p, size_request};
-    }
-#  elif defined(PLATFORM_HAS_VIRTUALALLOC2)
     template<bool committed>
     static void* reserve_aligned(size_t size) noexcept
     {
@@ -214,7 +183,8 @@ namespace snmalloc
       }
       return ret;
     }
-#  else
+#  endif
+
     static std::pair<void*, size_t> reserve_at_least(size_t size) noexcept
     {
       SNMALLOC_ASSERT(bits::is_pow2(size));
@@ -236,7 +206,6 @@ namespace snmalloc
       }
       error("Failed to allocate memory\n");
     }
-#  endif
 
     /**
      * Source of Entropy