pulsecore/shm: Remove shm_marker struct packing for pa_atomic_t fields

Taking addresses of fields in a packed struct are not guaranteed to be
aligned, resulting in warnings such as:

    ../src/pulsecore/shm.c: In function 'sharedmem_create':
    ../src/pulsecore/shm.c:198:25: error: taking address of packed member of 'struct shm_marker' may result in an unaligned pointer value [-Werror=address-of-packed-member]
      198 |         pa_atomic_store(&marker->pid, (int) getpid());
          |                         ^~~~~~~~~~~~

The struct already has its fields and types laid out in such a way that
the desired packing (without padding) is guaranteed - enforce this with
a `static_assert` to get rid of the unaligned pointer warning.

Change-Id: I012f97f2df3248c0285a3b4f594ae218bc81385e
Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/653>

diff --git a/src/pulsecore/shm.c b/src/pulsecore/shm.c
index 0742cb8..e464f6b 100644 (file)
--- a/src/pulsecore/shm.c
+++ b/src/pulsecore/shm.c
@@ -91,7 +91,10 @@ struct shm_marker {
     uint64_t _reserved2;
     uint64_t _reserved3;
     uint64_t _reserved4;
-} PA_GCC_PACKED;
+};
+
+// Ensure struct is appropriately packed
+static_assert(sizeof(struct shm_marker) == 8 * 5, "`struct shm_marker` is not tightly packed");
 
 static inline size_t shm_marker_size(pa_mem_type_t type) {
     if (type == PA_MEM_TYPE_SHARED_POSIX)