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authorKenneth Graunke <kenneth@whitecape.org>2014-01-03 15:08:33 -0800
committerAlan Coopersmith <alan.coopersmith@oracle.com>2014-01-03 15:31:19 -0800
commit3b72a2c9d1d656c74c691a45689e1d637f669e3a (patch)
tree85f45fe0c247fc7d331c8fdf306688b00d2c62ea
parent010872f611a044ced4e96b18a7514796b2a443df (diff)
Force XCB event structures with 64-bit extended fields to be packed.
With the advent of the Present extension, some events (such as PresentCompleteNotify) now use native 64-bit types on the wire. For XGE events, we insert an extra "uint32_t full_sequence" field immediately after the first 32 bytes of data. Normally, this causes the subsequent fields to be shifted over by 4 bytes, and the structure to grow in size by 4 bytes. Everything works fine. However, if event contains 64-bit extended fields, this may result in the compiler adding an extra 4 bytes of padding so that those fields remain aligned on 64-bit boundaries. This causes the structure to grow by 8 bytes, not 4. Unfortunately, XCB doesn't realize this, and always believes that the length only increased by 4. read_packet() then fails to malloc enough memory to hold the event, and the event processing code uses the wrong offsets. To fix this, mark any event structures containing 64-bit extended fields with __attribute__((__packed__)). v2: Use any(...) instead of True in (...), as suggested by Daniel Martin. v3 (Alan Coopersmith): Fix build with Solaris Studio 12.3 by moving the attribute to after the structure definition. Signed-off-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Keith Packard <keithp@keithp.com> [v1] Reviewed-by: Josh Triplett <josh@joshtriplett.org> [v1] Reviewed-by: Daniel Martin <consume.noise@gmail.com> Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
-rw-r--r--src/c_client.py12
-rw-r--r--src/xcb.h2
2 files changed, 11 insertions, 3 deletions
diff --git a/src/c_client.py b/src/c_client.py
index 99fd307..45de544 100644
--- a/src/c_client.py
+++ b/src/c_client.py
@@ -1762,7 +1762,7 @@ def c_simple(self, name):
# Iterator
_c_iterator(self, name)
-def _c_complex(self):
+def _c_complex(self, force_packed = False):
'''
Helper function for handling all structure types.
Called for all structs, requests, replies, events, errors.
@@ -1817,7 +1817,7 @@ def _c_complex(self):
if b.type.has_name:
_h(' } %s;', b.c_field_name)
- _h('} %s;', self.c_type)
+ _h('} %s%s;', 'XCB_PACKED ' if force_packed else '', self.c_type)
def c_struct(self, name):
'''
@@ -2902,6 +2902,7 @@ def c_event(self, name):
# events while generating the structure for them. Otherwise we would read
# garbage (the internal full_sequence) when accessing normal event fields
# there.
+ force_packed = False
if hasattr(self, 'is_ge_event') and self.is_ge_event and self.name == name:
event_size = 0
for field in self.fields:
@@ -2911,6 +2912,11 @@ def c_event(self, name):
full_sequence = Field(tcard32, tcard32.name, 'full_sequence', False, True, True)
idx = self.fields.index(field)
self.fields.insert(idx + 1, full_sequence)
+
+ # If the event contains any 64-bit extended fields, they need
+ # to remain aligned on a 64-bit boundary. Adding full_sequence
+ # would normally break that; force the struct to be packed.
+ force_packed = any(f.type.size == 8 and f.type.is_simple for f in self.fields[(idx+1):])
break
_c_type_setup(self, name, ('event',))
@@ -2920,7 +2926,7 @@ def c_event(self, name):
if self.name == name:
# Structure definition
- _c_complex(self)
+ _c_complex(self, force_packed)
else:
# Typedef
_h('')
diff --git a/src/xcb.h b/src/xcb.h
index e62c985..73c77a3 100644
--- a/src/xcb.h
+++ b/src/xcb.h
@@ -51,6 +51,8 @@ extern "C" {
* @file xcb.h
*/
+#define XCB_PACKED __attribute__((__packed__))
+
/**
* @defgroup XCB_Core_API XCB Core API
* @brief Core API of the XCB library.