Expand palloc/pg_malloc API for more type safety

This adds additional variants of palloc, pg_malloc, etc. that
encapsulate common usage patterns and provide more type safety.

Specifically, this adds palloc_object(), palloc_array(), and
repalloc_array(), which take the type name of the object to be
allocated as its first argument and cast the return as a pointer to
that type.  There are also palloc0_object() and palloc0_array()
variants for initializing with zero, and pg_malloc_*() variants of all
of the above.

Inspired by the talloc library.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/bb755632-2a43-d523-36f8-a1e7a389a907@enterprisedb.com

1 files changed, 22 insertions, 0 deletions

diff --git a/src/include/utils/palloc.h b/src/include/utils/palloc.h
index 332575f518a..a0b62aa7b0c 100644
--- a/src/include/utils/palloc.h
+++ b/src/include/utils/palloc.h
@@ -81,6 +81,28 @@ extern pg_nodiscard void *repalloc(void *pointer, Size size);
 extern void pfree(void *pointer);
 
 /*
+ * Variants with easier notation and more type safety
+ */
+
+/*
+ * Allocate space for one object of type "type"
+ */
+#define palloc_object(type) ((type *) palloc(sizeof(type)))
+#define palloc0_object(type) ((type *) palloc0(sizeof(type)))
+
+/*
+ * Allocate space for "count" objects of type "type"
+ */
+#define palloc_array(type, count) ((type *) palloc(sizeof(type) * (count)))
+#define palloc0_array(type, count) ((type *) palloc0(sizeof(type) * (count)))
+
+/*
+ * Change size of allocation pointed to by "pointer" to have space for "count"
+ * objects of type "type"
+ */
+#define repalloc_array(pointer, type, count) ((type *) repalloc(pointer, sizeof(type) * (count)))
+
+/*
  * The result of palloc() is always word-aligned, so we can skip testing
  * alignment of the pointer when deciding which MemSet variant to use.
  * Note that this variant does not offer any advantage, and should not be