Attachment 121770 Details for Bug 94136 – [3/4] DBusMessageIter: eliminate padding on 64-bit platforms

[patch] [3/4] DBusMessageIter: eliminate padding on 64-bit platforms

0003-DBusMessageIter-eliminate-padding-on-64-bit-platform.patch (text/plain), 2.82 KB, created by Simon McVittie on 2016-02-15 15:10:45 UTC

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Creator: Simon McVittie

Created: 2016-02-15 15:10:45 UTC

Size: 2.82 KB

patch

obsolete

>From 2b192b406ce0121c7e771b8f52cd0b6361bde2d6 Mon Sep 17 00:00:00 2001
>From: Simon McVittie <simon.mcvittie@collabora.co.uk>
>Date: Mon, 15 Feb 2016 15:00:22 +0000
>Subject: [PATCH 3/4] DBusMessageIter: eliminate padding on 64-bit platforms
>
>Previously, 64-bit (LP64 or LLP64) platforms would have had 32 bits
>of padding between pad2 and pad3. We want to guarantee that an ISO C
>compiler will copy the entire struct when assigning between structs,
>but padding is not guaranteed to be copied, so we want to ensure that
>the struct is "packed".
>
>Statically assert that the old ABI is compatible with the new ABI.
>
>Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
>Bug: https://bugs.freedesktop.org/show_bug.cgi?id=94136
>---
> dbus/dbus-message.c | 29 +++++++++++++++++++++++++++++
> dbus/dbus-message.h |  2 +-
> 2 files changed, 30 insertions(+), 1 deletion(-)
>
>diff --git a/dbus/dbus-message.c b/dbus/dbus-message.c
>index 50e87ca..4c34e96 100644
>--- a/dbus/dbus-message.c
>+++ b/dbus/dbus-message.c
>@@ -136,6 +136,29 @@ struct DBusMessageRealIter
>   } u; /**< the type writer or reader that does all the work */
> };
> 
>+/**
>+ * Layout of a DBusMessageIter on the stack in dbus 1.10.0. This is no
>+ * longer used, but for ABI compatibility we need to assert that the
>+ * new layout is the same size.
>+ */
>+typedef struct
>+{
>+  void *dummy1;
>+  void *dummy2;
>+  dbus_uint32_t dummy3;
>+  int dummy4;
>+  int dummy5;
>+  int dummy6;
>+  int dummy7;
>+  int dummy8;
>+  int dummy9;
>+  int dummy10;
>+  int dummy11;
>+  int pad1;
>+  int pad2;
>+  void *pad3;
>+} DBusMessageIter_1_10_0;
>+
> static void
> get_const_signature (DBusHeader        *header,
>                      const DBusString **type_str_p,
>@@ -2029,6 +2052,12 @@ _dbus_message_iter_init_common (DBusMessage         *message,
>   _DBUS_STATIC_ASSERT (sizeof (DBusMessageRealIter) <= sizeof (DBusMessageIter));
>   _DBUS_STATIC_ASSERT (_DBUS_ALIGNOF (DBusMessageRealIter) <=
>       _DBUS_ALIGNOF (DBusMessageIter));
>+  /* A failure of these two assertions would indicate that we've broken
>+   * ABI on this platform since 1.10.0. */
>+  _DBUS_STATIC_ASSERT (sizeof (DBusMessageIter_1_10_0) >=
>+      sizeof (DBusMessageIter));
>+  _DBUS_STATIC_ASSERT (_DBUS_ALIGNOF (DBusMessageIter_1_10_0) >=
>+      _DBUS_ALIGNOF (DBusMessageIter));
> 
>   /* Since the iterator will read or write who-knows-what from the
>    * message, we need to get in the right byte order
>diff --git a/dbus/dbus-message.h b/dbus/dbus-message.h
>index 3e33eb7..ac3e408 100644
>--- a/dbus/dbus-message.h
>+++ b/dbus/dbus-message.h
>@@ -62,7 +62,7 @@ struct DBusMessageIter
>   int dummy10;          /**< Don't use this */
>   int dummy11;          /**< Don't use this */
>   int pad1;             /**< Don't use this */
>-  int pad2;             /**< Don't use this */
>+  void *pad2;           /**< Don't use this */
>   void *pad3;           /**< Don't use this */
> };
> 
>-- 
>2.7.0
>

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Attachments on bug 94136: 121762 | 121768 | 121769 | 121770 | 121771

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