After compiling and linking with '-fsanitize=undefined' the following
error pops up in many tests:
vkd3d_shader_main.c:2024:12: runtime error: member access within null pointer of type 'struct vkd3d_shader_param_node'
This happens in the scenario where shader_param_allocator_get() gets
called with 'count = 0' but no allocation has been made yet, so
allocator->current is NULL.
In this case the result of the function, given by:
params = &allocator->current->param[allocator->index * allocator->stride];
is an invalid non-NULL pointer.
Functions like shader_sm4_read_instruction() may call
vsir_program_get_src_params() or vsir_program_get_dst_params() with 0
counts for various DCL_ instructions, as well as things like NOP,
ELSE, and SYNC.
We could avoid calling the functions in question with 0 counts, but it
doesn't seem worth the effort.
Alternatively, we could just return NULL on 'count == 0', but this is
also complicated because NULL is interpreted as a memory allocation
failure on the callers.
So we force allocation of the next node even if 'count = 0' when
allocator->current is NULL.
The other cases are similar and common code can be refactored.
Ideally the HLSL parser will eventually fit the same model, but that
will require more extensive work.
