This produces a new sync file with the given name which has the union of the
two original sync file's fences; redundant fences may be removed.
If one of the input sync files is signaled or invalid, then this function
may behave like dup(): the new file descriptor refers to the valid/unsignaled
sync file with its original name, rather than a new sync file.
The original fences remain valid, and the caller is responsible for closing
them.
Merge two sync files.
This produces a new sync file with the given name which has the union of the two original sync file's fences; redundant fences may be removed.
If one of the input sync files is signaled or invalid, then this function may behave like dup(): the new file descriptor refers to the valid/unsignaled sync file with its original name, rather than a new sync file.
The original fences remain valid, and the caller is responsible for closing them.
Available since API level 26.