The previous implementation was dereferencing the sample pointer in
order to get the offset to subtract from the member pointer. The
resulting value is then only used to get a pointer to the member in
order to calculate the offset so it doesn't actually read from the
memory location and shouldn't cause any problems. However this is
probably technically invalid and could have undefined behaviour. It
looks like clang takes advantage of this undefined behaviour and
doesn't actually offset the pointer. It also generates a warning when
it does this.
This patch splits the _cogl_container_of macro into two
implementations. Previously the macro was always used in the list
iterator macros like this:
SomeType *sample = _cogl_container_of(list_node, sample, link)
Instead of doing that there is now a new macro called
_cogl_list_set_iterator which explicitly assigns to the sample pointer
with an initial value before assigning to it again with the real
offset. This redundant initialisation gets optimised out by compiler.
The second macro is still called _cogl_container_of but instead of
taking a sample pointer it just directly takes the type name. That way
it can use the standard offsetof macro.
https://bugzilla.gnome.org/show_bug.cgi?id=723530
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 1efed1e0a2bce706eb4901979ed4e717bb13e4e2)
This removes cogl-queue.h and adds a copy of Wayland's embedded list
implementation. The advantage of the Wayland model is that it is much
simpler and so it is easier to follow. It also doesn't require
defining a typedef for every list type.
The downside is that there is only one list type which is a
doubly-linked list where the head has a pointer to both the beginning
and the end. The BSD implementation has many more combinations some of
which we were taking advantage of to reduce the size of critical
structs where we didn't need a pointer to the end of the list.
The corresponding changes to uses of cogl-queue.h are:
• COGL_STAILQ_* was used for onscreen the list of events and dirty
notifications. This makes the size of the CoglContext grow by one
pointer.
• COGL_TAILQ_* was used for fences.
• COGL_LIST_* for CoglClosures. In this case the list head now has an
extra pointer which means CoglOnscreen will grow by the size of
three pointers, but this doesn't seem like a particularly important
struct to optimise for size anyway.
• COGL_LIST_* was used for the list of foreign GLES2 offscreens.
• COGL_TAILQ_* was used for the list of sub stacks in a
CoglMemoryStack.
• COGL_LIST_* was used to track the list of layers that haven't had
code generated yet while generating a fragment shader for a
pipeline.
• COGL_LIST_* was used to track the pipeline hierarchy in CoglNode.
The last part is a bit more controversial because it increases the
size of CoglPipeline and CoglPipelineLayer by one pointer in order to
have the redundant tail pointer for the list head. Normally we try to
be very careful about the size of the CoglPipeline struct. Because
CoglPipeline is slice-allocated, this effectively ends up adding two
pointers to the size because GSlice rounds up to the size of two
pointers.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 13abf613b15f571ba1fcf6d2eb831ffc6fa31324)
Conflicts:
cogl/cogl-context-private.h
cogl/cogl-context.c
cogl/driver/gl/cogl-pipeline-fragend-glsl.c
doc/reference/cogl-2.0-experimental/Makefile.am
