srctree

Alex Kladov parent 1e5075f8 ff18103e
std: improve std.once tests

  • * fix UB when Thread.spawn fails, and we try to join uninitialized
  • threads (through new thread_count variable).
  • * make sure that the tests pins down synchronization guarantees: in the
  • main thread, we can observe 1 due to synchronization from
  • Thread.join(). To make sure that once uses Acq/Rel, and not just
  • relaxed, we should also additionally check that each thread observes
  • 1, regardless of whether it was the one to call once.
inlinesplit
lib/std/once.zig added: 6, removed: 2, total 4
@@ -7,6 +7,7 @@ pub fn once(comptime f: fn () void) Once(f) {
}
 
/// An object that executes the function `f` just once.
/// It is undefined behavior if `f` re-enters the same Once instance.
pub fn Once(comptime f: fn () void) type {
return struct {
done: bool = false,
@@ -51,15 +52,18 @@ test "Once executes its function just once" {
global_once.call();
} else {
var threads: [10]std.Thread = undefined;
defer for (threads) |handle| handle.join();
var thread_count: usize = 0;
defer for (threads[0..thread_count]) |handle| handle.join();
 
for (&threads) |*handle| {
handle.* = try std.Thread.spawn(.{}, struct {
fn thread_fn(x: u8) void {
_ = x;
global_once.call();
if (global_number != 1) @panic("memory ordering bug");
}
}.thread_fn, .{0});
thread_count += 1;
}
}