3 files changed, 12 insertions, 4 deletions
diff --git a/ChangeLog b/ChangeLog
index daa1bbde..744443f0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2017-04-10         Andrew J. Schorr     <aschorr@telemetry-investments.com>
+
+	* awk.h (enum opcodeval): For the avoidance of doubt, specify that
+	Op_illegal must equal zero.
+	* symbol.c (bcfree): Improve clarity by setting opcode to Op_illegal
+	instead of 0.
+	(free_bc_mempool): Improve clarity by comparing opcode to Op_illegal
+	instead of to 0.
+
 2017-04-10         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* symbol.c (free_bc_mempool): Change `first' from int to bool.
diff --git a/awk.h b/awk.h
index c7bfec2b..5cad2044 100644
--- a/awk.h
+++ b/awk.h
@@ -597,8 +597,7 @@ typedef enum lintvals {
 /* --------------------------------Instruction ---------------------------------- */
 
 typedef enum opcodeval {
-	/* illegal entry == 0 */
-	Op_illegal,
+	Op_illegal = 0,		/* illegal entry */
 
 	/* binary operators */
 	Op_times,
diff --git a/symbol.c b/symbol.c
index 51e3cf23..ea5ee0af 100644
--- a/symbol.c
+++ b/symbol.c
@@ -714,7 +714,7 @@ bcfree(INSTRUCTION *cp)
 {
 	assert(cp->pool_size >= 1 && cp->pool_size <= MAX_INSTRUCTION_ALLOC);
 
-	cp->opcode = 0;
+	cp->opcode = Op_illegal;
 	cp->nexti = pools->pool[cp->pool_size - 1].free_list;
 	pools->pool[cp->pool_size - 1].free_list = cp;
 }
@@ -924,7 +924,7 @@ free_bc_mempool(struct instruction_mem_pool *pool, int size)
 
 		end = (first ? pool->free_space : & block->i[INSTR_CHUNK]);
 		for (cp = & block->i[0]; cp + size <= end; cp += size) {
-			if (cp->opcode != 0)
+			if (cp->opcode != Op_illegal)
 				free_bc_internal(cp);
 		}
 		next = block->next;