Merge pull request #23 from Microsoft/comment

Fix comment to represent current PAL API.

src/mem/alloc.h

@@ -943,7 +943,7 @@ namespace snmalloc
         {
           super_available.remove(super);
 
-          if (decommit_strategy == DecommitSuper)
+          if constexpr (decommit_strategy == DecommitSuper)
           {
             large_allocator.memory_provider.notify_not_using(
               (void*)((size_t)super + OS_PAGE_SIZE),
@@ -1027,7 +1027,7 @@ namespace snmalloc
           sc->remove(slab);
         }
 
-        if (decommit_strategy == DecommitSuper)
+        if constexpr (decommit_strategy == DecommitSuper)
         {
           large_allocator.memory_provider.notify_not_using(
             (void*)((size_t)slab + OS_PAGE_SIZE),

src/mem/largealloc.h

@@ -138,7 +138,7 @@ namespace snmalloc
     {
       if (((size_t)reserved_start + need) > (size_t)reserved_end)
       {
-        if (allow_reserve == YesReserve)
+        if constexpr (allow_reserve == YesReserve)
         {
           stats.segment_create();
           reserved_start =
@@ -191,10 +191,13 @@ namespace snmalloc
       {
         if ((decommit_strategy != DecommitNone) || (large_class > 0))
         {
-          // Only the first page needs to be zeroed, as this was decommitted.
-          if (zero_mem == YesZero)
+          // The first page is already in "use" for the stack element,
+          // this will need zeroing for a YesZero call.
+          if constexpr (zero_mem == YesZero)
             memory_provider.template zero<true>(p, OS_PAGE_SIZE);
 
+          // Notify we are using the rest of the allocation.
+          // Passing zero_mem ensures the PAL provides zeroed pages if required.
           memory_provider.template notify_using<zero_mem>(
             (void*)((size_t)p + OS_PAGE_SIZE),
             bits::align_up(size, OS_PAGE_SIZE) - OS_PAGE_SIZE);
@@ -202,7 +205,7 @@ namespace snmalloc
         else
         {
           // This is a superslab that has not been decommitted.
-          if (zero_mem == YesZero)
+          if constexpr (zero_mem == YesZero)
             memory_provider.template zero<true>(
               p, bits::align_up(size, OS_PAGE_SIZE));
         }

src/mem/mediumslab.h

@@ -86,9 +86,9 @@ namespace snmalloc
       assert(bits::is_aligned_block<OS_PAGE_SIZE>(p, OS_PAGE_SIZE));
       size = bits::align_up(size, OS_PAGE_SIZE);
 
-      if (decommit_strategy == DecommitAll)
+      if constexpr (decommit_strategy == DecommitAll)
         memory_provider.template notify_using<zero_mem>(p, size);
-      else if (zero_mem == YesZero)
+      else if constexpr (zero_mem == YesZero)
         memory_provider.template zero<true>(p, size);
 
       return p;
@@ -104,7 +104,7 @@ namespace snmalloc
       free++;
       stack[--head] = pointer_to_index(p);
 
-      if (decommit_strategy == DecommitAll)
+      if constexpr (decommit_strategy == DecommitAll)
         memory_provider.notify_not_using(p, sizeclass_to_size(sizeclass));
 
       return was_full;

src/mem/superslab.h

@@ -169,7 +169,7 @@ namespace snmalloc
       meta[0].sizeclass = sizeclass;
       meta[0].link = SLABLINK_INDEX;
 
-      if (decommit_strategy == DecommitAll)
+      if constexpr (decommit_strategy == DecommitAll)
       {
         memory_provider.template notify_using<NoZero>(
           (void*)((size_t)this + OS_PAGE_SIZE), SLAB_SIZE - OS_PAGE_SIZE);
@@ -194,7 +194,7 @@ namespace snmalloc
       head = h + n + 1;
       used += 2;
 
-      if (decommit_strategy == DecommitAll)
+      if constexpr (decommit_strategy == DecommitAll)
       {
         memory_provider.template notify_using<NoZero>(slab, SLAB_SIZE);
       }
@@ -216,7 +216,7 @@ namespace snmalloc
       bool was_almost_full = is_almost_full();
       used -= 2;
 
-      if (decommit_strategy == DecommitAll)
+      if constexpr (decommit_strategy == DecommitAll)
         memory_provider.notify_not_using(slab, SLAB_SIZE);
 
       assert(meta[index].is_unused());
@@ -231,7 +231,7 @@ namespace snmalloc
     Action dealloc_short_slab(MemoryProvider& memory_provider)
     {
       // This is the short slab.
-      if (decommit_strategy == DecommitAll)
+      if constexpr (decommit_strategy == DecommitAll)
       {
         memory_provider.notify_not_using(
           (void*)((size_t)this + OS_PAGE_SIZE), SLAB_SIZE - OS_PAGE_SIZE);

src/pal/pal_freebsd.h

@@ -33,7 +33,7 @@ namespace snmalloc
     {
       assert(
         bits::is_aligned_block<OS_PAGE_SIZE>(p, size) || (zero_mem == NoZero));
-      if (zero_mem == YesZero)
+      if constexpr (zero_mem == YesZero)
         zero(p, size);
     }
 

src/pal/pal_linux.h

@@ -36,7 +36,7 @@ namespace snmalloc
       assert(
         bits::is_aligned_block<OS_PAGE_SIZE>(p, size) || (zero_mem == NoZero));
 
-      if (zero_mem == YesZero)
+      if constexpr (zero_mem == YesZero)
         zero<true>(p, size);
     }