lei: use RENAME_NOREPLACE on Linux 3.15+

One syscall is better than two for atomicity in Maildirs.  This
means there's no window where another process can see both the
old and new file at the same time (link && unlink), nor a window
where we might inadvertantly clobber an existing file if we were
to do `stat && rename'.

1 files changed, 7 insertions, 1 deletions

diff --git a/devel/syscall-list b/devel/syscall-list
index b33401d9..3d55df1f 100755
--- a/devel/syscall-list
+++ b/devel/syscall-list
@@ -1,4 +1,4 @@
-# Copyright 2021 all contributors <meta@public-inbox.org>
+# Copyright all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <http://www.gnu.org/licenses/agpl-3.0.txt>
 # Dump syscall numbers under Linux and any other kernel which
 # promises stable syscall numbers.  This is to maintain
@@ -9,7 +9,10 @@
 eval 'exec perl -S $0 ${1+"$@"}' # no shebang
         if 0; # running under some shell
 use strict;
+use v5.10.1;
 use File::Temp 0.19;
+use POSIX qw(uname);
+say '$machine='.(POSIX::uname())[-1];
 my $cc = $ENV{CC} // 'cc';
 my @cflags = split(/\s+/, $ENV{CFLAGS} // '-Wall');
 my $str = do { local $/; <DATA> };
@@ -43,6 +46,9 @@ int main(void)
         D(SYS_inotify_add_watch);
         D(SYS_inotify_rm_watch);
         D(SYS_prctl);
+#ifdef SYS_renameat2
+        D(SYS_renameat2);
+#endif
 #endif /* Linux, any other OSes with stable syscalls? */
         printf("size_t=%zu off_t=%zu\n", sizeof(size_t), sizeof(off_t));
         return 0;