3 files changed, 27 insertions, 5 deletions
diff --git a/src/include/c.h b/src/include/c.h
index b0f98d46a35..e8df5a23dd9 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -361,13 +361,29 @@ typedef unsigned long long int uint64;
 
 /*
  * 128-bit signed and unsigned integers
- *		There currently is only a limited support for the type. E.g. 128bit
- *		literals and snprintf are not supported; but math is.
+ *		There currently is only limited support for such types.
+ *		E.g. 128bit literals and snprintf are not supported; but math is.
+ *		Also, because we exclude such types when choosing MAXIMUM_ALIGNOF,
+ *		it must be possible to coerce the compiler to allocate them on no
+ *		more than MAXALIGN boundaries.
  */
 #if defined(PG_INT128_TYPE)
-#define HAVE_INT128
-typedef PG_INT128_TYPE int128;
-typedef unsigned PG_INT128_TYPE uint128;
+#if defined(pg_attribute_aligned) || ALIGNOF_PG_INT128_TYPE <= MAXIMUM_ALIGNOF
+#define HAVE_INT128 1
+
+typedef PG_INT128_TYPE int128
+#if defined(pg_attribute_aligned)
+pg_attribute_aligned(MAXIMUM_ALIGNOF)
+#endif
+;
+
+typedef unsigned PG_INT128_TYPE uint128
+#if defined(pg_attribute_aligned)
+pg_attribute_aligned(MAXIMUM_ALIGNOF)
+#endif
+;
+
+#endif
 #endif
 
 /*
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 95d30d16b68..4931f4cf80e 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -27,6 +27,9 @@
 /* The normal alignment of `long long int', in bytes. */
 #undef ALIGNOF_LONG_LONG_INT
 
+/* The normal alignment of `PG_INT128_TYPE', in bytes. */
+#undef ALIGNOF_PG_INT128_TYPE
+
 /* The normal alignment of `short', in bytes. */
 #undef ALIGNOF_SHORT
 
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index 13b35d0afa2..73636ea57ea 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -34,6 +34,9 @@
 /* The alignment requirement of a `long long int'. */
 #define ALIGNOF_LONG_LONG_INT 8
 
+/* The normal alignment of `PG_INT128_TYPE', in bytes. */
+#undef ALIGNOF_PG_INT128_TYPE
+
 /* The alignment requirement of a `short'. */
 #define ALIGNOF_SHORT 2