Always evaluate to NULL when the source Picture is not located in the
MpegEncContext.picture array. That will only happen for
next/last_picture_ptr when updating the thread context during h264 frame
threaded decoding, where they will point to elements of ref_list. Since
ref_list is not copied during updating the context and is invalid until
it is constructed for the current slice, there is no point in doing
anything complicated with next/last_picture_ptr, as they will get
updated when the ref_list is filled.
On Cygwin systems MinGW headers can be present if the corresponding
packages have been installed. Since the MinGW libc is checked for
first, this results in newlib getting misdetected as MinGW libc.
REBASE_PICTURE (more specifically, this half of it) takes a Picture
pointer that points into one larger struct, finds the offset of
that Picture within the struct and finds the corresponding field
within another instance of a similar struct.
The pointer difference "pic - (Picture*)old_ctx" is a value given
in sizeof(Picture) units, and when applied back on
(Picture*)new_ctx gets multiplied back with sizeof(Picture). Many
compilers seem to optimize out this division/multiplication, but
not all do.
GCC 4.2 on OS X doesn't seem to remove the division/multiplication,
therefore the new pointer didn't turn out to point to exactly
the right place in the new struct since it only had sizeof(Picture)
granularity (and the Picture is not aligned on a sizeof(Picture)
boundary within the encompassing struct). This bug has been present
before 47318953d as well - with H264, pointers to h->ref_list[0][0]
pointed to 88 bytes before h->ref_list[0][0] after the rebase. After
shrinking Picture, the difference ended up even larger, making
writes via such a Picture pointer overwrite other fields at random
in H264Context, ending up in crashes later.
This fixes H264 multithreaded decoding on OS X with GCC 4.2.
Signed-off-by: Martin Storsjö <martin@martin.st>
This makes the plain-armv6 version use the same registers as the
armv6t2 version above.
This fixes fate-vp8 on plain-armv6 devices.
Signed-off-by: Martin Storsjö <martin@martin.st>
