Somehow I got the idea that compound literals had function-scoped
lifetime. Instead, like all other objects with automatic storage
duration, compound literals are block-scoped, so they become invalid
after exiting the block they were declared in. It seems like a recent
change to GCC actually reuses the memory that the compound literals
used to occupy, which was causing a few bugs.
The pattern of conditionally assigning a pointer to a compound literal
was used in a few places in ra_d3d11 where the Direct3D API expects
either a pointer to an initialised struct or NULL. Change these to
ensure the lifetime of the struct includes the API call.
Should fix#6775.
80552ab28e