pkmem: handle accessing uninitialized debug blocks

1 files changed, 23 insertions, 3 deletions

diff --git a/pkmem.h b/pkmem.h
index 50e251d..2339d22 100644
--- a/pkmem.h
+++ b/pkmem.h
@@ -251,6 +251,8 @@ pk_mem_bucket_create(const char* description, int64_t sz, enum PK_MEMBUCKET_FLAG
 	bkt->debug_head_r = 0;
 	bkt->debug_block_capacity = 128;
 	bkt->debug_blocks = (struct pk_memblock*)aligned_alloc(alignof(struct pk_memblock), sizeof(struct pk_memblock) * 128);
+	bkt->debug_blocks[0].ptr = NULL;
+	bkt->debug_blocks[0].size = 0;
 #endif
 
 	return bkt;
@@ -269,7 +271,7 @@ pk_mem_bucket_destroy(struct pk_membucket* bkt)
 void
 pk_mem_bucket_reset(struct pk_membucket* bkt)
 {
-	if (PK_HAS_FLAG(bkt->flags, PK_MEMBUCKET_FLAG_TRANSIENT) == true) {
+	if (PK_HAS_FLAG(bkt->flags, PK_MEMBUCKET_FLAG_TRANSIENT) == false) {
 		PK_LOG_ERR("WARNING: pk_bucket_reset called on non-transient pk_membucket\n");
 	}
 	bkt->head = 0;
@@ -288,6 +290,8 @@ pk_mem_bucket_reset(struct pk_membucket* bkt)
 #ifdef PK_MEMORY_DEBUGGER
 	bkt->debug_head_l = 0;
 	bkt->debug_head_r = 0;
+	bkt->debug_blocks[0].ptr = NULL;
+	bkt->debug_blocks[0].size = 0;
 #endif
 }
 
@@ -330,6 +334,7 @@ pk_bucket_insert_block(struct pk_membucket* bkt, const struct pk_memblock* block
 			break;
 		}
 	}
+	assert(old_block != NULL);
 	if (i == 0 && old_block != NULL) {
 		*old_block = *block;
 	} else {
@@ -414,20 +419,32 @@ pk_new_bkt(size_t sz, size_t alignment, struct pk_membucket* bkt)
 
 			if (bkt->debug_head_r == bkt->debug_block_capacity) {
 				struct pk_memblock *debug_blocks;
-				debug_blocks = (struct pk_memblock*)aligned_alloc(alignof(struct pk_memblock), sizeof(struct pk_memblock) * bkt->debug_block_capacity + 128);
+				debug_blocks = (struct pk_memblock*)aligned_alloc(alignof(struct pk_memblock), sizeof(struct pk_memblock) * (bkt->debug_block_capacity + 128));
 				assert(debug_blocks != NULL);
 				memcpy(debug_blocks, bkt->debug_blocks, sizeof(struct pk_memblock) * bkt->debug_block_capacity);
 				free(bkt->debug_blocks);
 				bkt->debug_blocks = debug_blocks;
+				bkt->debug_block_capacity += 128;
 			}
 
+			bkt->debug_blocks[bkt->debug_head_r].ptr = NULL;
+			bkt->debug_blocks[bkt->debug_head_r].size = 0;
+
 		} else {
+			// 2025-06-05 JCB
+			// This intentionally looks at debug_head_r, which could potentially
+			//  be uninitialized. I added some logic elsewhere to ensure that
+			//  whenever debug_head_r is incremented, we set the related block
+			//  to NULL/0 so that this will catch size==0.
+			// I was experiencing an issue where in testing it was initialized to
+			//  NULL/0, but then in a client application it was garbage data.
 			for (ii = bkt->debug_head_l+1; ii <= bkt->debug_head_r; ++ii) {
 				if (bkt->debug_blocks[ii].size == 0) {
 					bkt->debug_head_l = ii;
 					break;
 				}
 			}
+			assert(ii != bkt->debug_head_r+1);
 		}
 		assert(bkt->debug_head_l <= bkt->debug_head_r);
 		bkt->debug_blocks[i].data = (char*)data;
@@ -516,7 +533,10 @@ pk_delete_bkt(const void* ptr, size_t sz, struct pk_membucket* bkt)
 				if (i <= bkt->debug_head_l) {
 					bkt->debug_head_l = i-1;
 				}
-				if (i == bkt->debug_head_r) {
+				if (i == bkt->debug_head_r+1) {
+					if (bkt->debug_head_l == bkt->debug_head_r) {
+						bkt->debug_head_l--;
+					}
 					bkt->debug_head_r--;
 				}
 				assert(bkt->debug_head_l <= bkt->debug_head_r);