https://lists.gnu.org/archive/html/bug-bash/2026-03/msg00069.html
From 7309ee9f263dfcaf11eeca679cfec5cf5c8f9455 Mon Sep 17 00:00:00 2001
Message-ID: <7309ee9f263dfcaf11eeca679cfec5cf5c8f9455.1774896688.git.sam@gentoo.org>
From: Sam James
Date: Mon, 30 Mar 2026 19:19:33 +0100
Subject: [PATCH] general: workaround aliasing violation in REVERSE_LIST macro
In jobs.c, say, we have:
```
p->next = (PROCESS *)NULL;
newjob->pipe = REVERSE_LIST (the_pipeline, PROCESS *);
for (p = newjob->pipe; p->next; p = p->next)
```
REVERSE_LIST (-> list_reverse) reverses the linked list `the_pipeline`
while doing accesses as GENERIC_LIST*, but the original elements are PROCESS*.
I think GCC has an exemption for doing this with void* but even that isn't
required to work by the standard. I think it either needs to be done with char*
or with GENERIC_LIST marked with __attribute__((may_alias))
(though that isn't portable).
For Gentoo, the alias approach is fine until this gets fixed upstream,
so do that.
This fixes bash being miscompiled by GCC 16 with -O2 -flto and USE=-plugins
(for -rdynamic to be dropped).
Bug: https://bugs.gentoo.org/971782
Signed-off-by: Sam James
---
general.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/general.h b/general.h
index 5b1eac08..883939a7 100644
--- general.h
+++ general.h
@@ -122,7 +122,7 @@ extern char *strcpy (char *, const char *);
can be written to handle the general case for linked lists. */
typedef struct g_list {
struct g_list *next;
-} GENERIC_LIST;
+} __attribute__((may_alias)) GENERIC_LIST;
/* Here is a generic structure for associating character strings
with integers. It is used in the parser for shell tokenization. */
base-commit: 637f5c8696a6adc9b4519f1cd74aa78492266b7f
--
2.53.0