[2.32] struct _Unwind_Exception alignment should not depend on compiler flags
Matheus Castanho
msc@linux.ibm.com
Mon Nov 16 20:46:59 GMT 2020
From: Florian Weimer <fweimer@redhat.com>
Hi Florian and Tulio,
Could we backport this patch to the 2.32 branch? It would be helpful to fix the
issue downstream.
Thanks,
Matheus Castanho
---8<---
__attribute__((__aligned__)) selects an alignment that depends on
the micro-architecture selected by GCC flags. Enabling vector
extensions may increase the allignment. This is a problem when
building glibc as a collection of ELF multilibs with different
GCC flags because ld.so and libc.so/libpthread.so/&c may end up
with a different layout of struct pthread because of the
changing offset of its struct _Unwind_Exception field.
Tested-By: Matheus Castanho <msc@linux.ibm.com>
(cherry picked from commit 30af7c7fa13e17d82c3f1f91536384715844f432)
---
sysdeps/generic/unwind.h | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/sysdeps/generic/unwind.h b/sysdeps/generic/unwind.h
index b667a5b652..c229603af3 100644
--- a/sysdeps/generic/unwind.h
+++ b/sysdeps/generic/unwind.h
@@ -75,15 +75,21 @@ typedef void (*_Unwind_Exception_Cleanup_Fn) (_Unwind_Reason_Code,
struct _Unwind_Exception
{
- _Unwind_Exception_Class exception_class;
- _Unwind_Exception_Cleanup_Fn exception_cleanup;
- _Unwind_Word private_1;
- _Unwind_Word private_2;
-
- /* @@@ The IA-64 ABI says that this structure must be double-word aligned.
- Taking that literally does not make much sense generically. Instead we
- provide the maximum alignment required by any type for the machine. */
-} __attribute__((__aligned__));
+ union
+ {
+ struct
+ {
+ _Unwind_Exception_Class exception_class;
+ _Unwind_Exception_Cleanup_Fn exception_cleanup;
+ _Unwind_Word private_1;
+ _Unwind_Word private_2;
+ };
+
+ /* The IA-64 ABI says that this structure must be double-word aligned. */
+ _Unwind_Word unwind_exception_align[2]
+ __attribute__ ((__aligned__ (2 * sizeof (_Unwind_Word))));
+ };
+};
/* The ACTIONS argument to the personality routine is a bitwise OR of one
--
2.26.2
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