Re: Reducing the chunk header sizes on all memory context types

[David Rowley]

On Wed, 31 Aug 2022 at 03:31, David Rowley <dgrowle...@gmail.com> wrote:
> I've no objections to adding a comment to the enum to
> explain to future devs. My vote would be for that and add the (int)
> cast as proposed by Robert.

Here's a patch which adds a comment to MemoryContextMethodID to Robert's patch.

David

diff --git a/src/include/utils/memutils_internal.h 
b/src/include/utils/memutils_internal.h
index 9a9f52ef16..f348282a07 100644
--- a/src/include/utils/memutils_internal.h
+++ b/src/include/utils/memutils_internal.h
@@ -74,6 +74,9 @@ extern void SlabCheck(MemoryContext context);
  * MemoryContextMethodID
  *             A unique identifier for each MemoryContext implementation which
  *             indicates the index into the mcxt_methods[] array. See mcxt.c.
+ *             The maximum value for this enum is constrained by
+ *             MEMORY_CONTEXT_METHODID_MASK.  If an enum value higher than 
that is
+ *             required then MEMORY_CONTEXT_METHODID_BITS will need to be 
increased.
  */
 typedef enum MemoryContextMethodID
 {
diff --git a/src/include/utils/memutils_memorychunk.h 
b/src/include/utils/memutils_memorychunk.h
index 685c177b68..2eefc138e3 100644
--- a/src/include/utils/memutils_memorychunk.h
+++ b/src/include/utils/memutils_memorychunk.h
@@ -159,7 +159,7 @@ MemoryChunkSetHdrMask(MemoryChunk *chunk, void *block,
        Assert((char *) chunk > (char *) block);
        Assert(blockoffset <= MEMORYCHUNK_MAX_BLOCKOFFSET);
        Assert(value <= MEMORYCHUNK_MAX_VALUE);
-       Assert(methodid <= MEMORY_CONTEXT_METHODID_MASK);
+       Assert((int) methodid <= MEMORY_CONTEXT_METHODID_MASK);
 
        chunk->hdrmask = (((uint64) blockoffset) << 
MEMORYCHUNK_BLOCKOFFSET_BASEBIT) |
                (((uint64) value) << MEMORYCHUNK_VALUE_BASEBIT) |
@@ -175,7 +175,7 @@ static inline void
 MemoryChunkSetHdrMaskExternal(MemoryChunk *chunk,
                                                          MemoryContextMethodID 
methodid)
 {
-       Assert(methodid <= MEMORY_CONTEXT_METHODID_MASK);
+       Assert((int) methodid <= MEMORY_CONTEXT_METHODID_MASK);
 
        chunk->hdrmask = MEMORYCHUNK_MAGIC | (((uint64) 1) << 
MEMORYCHUNK_EXTERNAL_BASEBIT) |
                methodid;