From 00365a7beb45d5c87823434d65004a5a84c197fe Mon Sep 17 00:00:00 2001
From: Maarten Boot <11140490+maarten-boot@users.noreply.github.com>
Date: Tue, 3 Nov 2026 09:24:02 +0100
Subject: [PATCH] ass: keep the areas of its allocator aligned for the host

getarea() rounds sizes to sizeof(int) and splits free blocks from the
end, so after a name (strlen + 1 bytes) the next area is at 4 (mod 8),
and the structs kept there (line_t, relc_t, locl_t, stat_t and the
allocator's own freeblock, all with pointers) are misaligned on a 64-bit
host: -fsanitize=alignment reports 919 accesses in em_ass when the em22
examples are linked.

Round all sizes to _Alignof(max_align_t), and to at least the size of a
free block's header, as led does since its alignment fix; align the
workspace in main()'s frame that is given to the allocator at start.
em_ass's output is unchanged (the seven em22 examples are identical).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 util/ass/ass00.c |  3 ++-
 util/ass/asscm.c | 23 ++++++++++++++++++++---
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/util/ass/ass00.c b/util/ass/ass00.c
index 3a0500748..faa0e2c7b 100644
--- a/util/ass/ass00.c
+++ b/util/ass/ass00.c
@@ -48,7 +48,8 @@ int main(int argc, char** argv)
 	 *   The d flag can be repeated several times, resulting in more
 	 *        debugging information.
 	 */
-	char workspace[6000];
+	/* Given to the allocator (asscm.c): aligned as its areas must be. */
+	_Alignas(max_align_t) char workspace[6000];
 	char* cp;
 	int argno;
 
diff --git a/util/ass/asscm.c b/util/ass/asscm.c
index c6886a3fd..42603961f 100644
--- a/util/ass/asscm.c
+++ b/util/ass/asscm.c
@@ -18,6 +18,7 @@
  The algorithm is first fit.
  */
 
+#include <stddef.h>
 #include <stdint.h>
 #include <stdbool.h>
 #include "ass00.h"
@@ -41,13 +42,29 @@ static struct freeblock freexx[2] = { { freexx, 0 }, { freexx + 1, 0 } };
 
 #define CHUNK 2048 /* Smallest chunk to be gotten from UNIX */
 
+/*
+ * Every area and every free block starts at a multiple of ALIGN, so that
+ * the structs kept in them (line_t, relc_t, locl_t, ... with pointers: 8
+ * bytes on a 64-bit host) are aligned: malloc() returns such addresses,
+ * and all sizes are rounded up to ALIGN. A free block must also have room
+ * for its own header.
+ */
+#define ALIGN _Alignof(max_align_t)
+
+static unsigned int roundsize(unsigned int size)
+{
+	if (size < sizeof(struct freeblock))
+		size = sizeof(struct freeblock);
+	return (size + (ALIGN - 1)) & ~(unsigned int)(ALIGN - 1);
+}
+
 area_t getarea(unsigned int size)
 {
 	struct freeblock *c_ptr, *l_ptr;
 	char* ptr;
 	unsigned rqsize;
 
-	size = ((size + (sizeof(int) - 1)) / sizeof(int)) * sizeof(int);
+	size = roundsize(size);
 #ifdef MEMUSE
 	m_used += size;
 	m_free -= size;
@@ -75,7 +92,7 @@ area_t getarea(unsigned int size)
 			if (ptr)
 				break; /* request succesfull */
 			rqsize /= 2;
-			rqsize -= rqsize % sizeof(int);
+			rqsize -= rqsize % ALIGN;
 			if (rqsize < sizeof freehead)
 			{
 				fatal("Out of memory");
@@ -93,7 +110,7 @@ void freearea(area_t ptr, unsigned int size)
 {
 	struct freeblock *c_ptr, *l_ptr;
 
-	size = ((size + (sizeof(int) - 1)) / sizeof(int)) * sizeof(int);
+	size = roundsize(size);
 #ifdef MEMUSE
 	m_free += size;
 	m_used -= size;