diff --git a/lib/std/child_process.zig b/lib/std/child_process.zig index a7ca89c6a5..a76dfd3528 100644 --- a/lib/std/child_process.zig +++ b/lib/std/child_process.zig @@ -282,17 +282,36 @@ pub const ChildProcess = struct { fn cleanupAfterWait(self: *ChildProcess, status: u32) !Term { defer destroyPipe(self.err_pipe); - // Write maxInt(ErrInt) to the write end of the err_pipe. This is after - // waitpid, so this write is guaranteed to be after the child - // pid potentially wrote an error. This way we can do a blocking - // read on the error pipe and either get maxInt(ErrInt) (no error) or - // an error code. - try writeIntFd(self.err_pipe[1], maxInt(ErrInt)); - const err_int = try readIntFd(self.err_pipe[0]); - // Here we potentially return the fork child's error - // from the parent pid. - if (err_int != maxInt(ErrInt)) { - return @errSetCast(SpawnError, @intToError(err_int)); + if (builtin.os == .linux) { + var fd = [1]std.os.pollfd{std.os.pollfd{ + .fd = self.err_pipe[0], + .events = std.os.POLLIN, + .revents = undefined, + }}; + + // Check if the eventfd buffer stores a non-zero value by polling + // it, that's the error code returned by the child process. + _ = std.os.poll(&fd, 0) catch unreachable; + + // According to eventfd(2) the descriptro is readable if the counter + // has a value greater than 0 + if ((fd[0].revents & std.os.POLLIN) != 0) { + const err_int = try readIntFd(self.err_pipe[0]); + return @errSetCast(SpawnError, @intToError(err_int)); + } + } else { + // Write maxInt(ErrInt) to the write end of the err_pipe. This is after + // waitpid, so this write is guaranteed to be after the child + // pid potentially wrote an error. This way we can do a blocking + // read on the error pipe and either get maxInt(ErrInt) (no error) or + // an error code. + try writeIntFd(self.err_pipe[1], maxInt(ErrInt)); + const err_int = try readIntFd(self.err_pipe[0]); + // Here we potentially return the fork child's error from the parent + // pid. + if (err_int != maxInt(ErrInt)) { + return @errSetCast(SpawnError, @intToError(err_int)); + } } return statusToTerm(status);