exec: Avoid a warning when building with _FORTIFY_SOURCE

Also, don't pass the address of errno itself to write(), since write()
is allowed to modify it.

1 files changed, 6 insertions, 1 deletions

diff --git a/exec.c b/exec.c
index 489953e..3fa5789 100644
--- a/exec.c
+++ b/exec.c
@@ -382,8 +382,13 @@ static int bfs_exec_spawn(const struct bfs_exec *execbuf) {
 		}
 
 		execvp(execbuf->argv[0], execbuf->argv);
+
+		int error;
 	child_err:
-		write(pipefd[1], &errno, sizeof(errno));
+		error = errno;
+		if (write(pipefd[1], &error, sizeof(error)) != sizeof(error)) {
+			// Parent will still see that we exited unsuccessfully, but won't know why
+		}
 		close(pipefd[1]);
 		_Exit(EXIT_FAILURE);
 	}