This saves a syscall on every source file open, &c.;
F_DUPFD_CLOEXEC is a mandatory part of POSIX since Issue 7
(Austin Group Interpretation 1003.1-2001 #171).
---
autoconf bits adapted almost-verbatim from the st_mtim check above
configure.ac | 13 +++++++++++++
src/redir.c | 7 +++++++
2 files changed, 20 insertions(+)
diff --git a/configure.ac b/configure.ac
index 52aa429..b870a59 100644
--- a/configure.ac
+++ b/configure.ac
@@ -177,6 +177,19 @@ if test "$have_st_mtim" = "yes"; then
[Define if your `struct stat' has `st_mtim'])
fi
+dnl F_DUPFD_CLOEXEC is a mandatory part of POSIX since Issue 7
+AC_MSG_CHECKING(for F_DUPFD_CLOEXEC)
+AC_COMPILE_IFELSE(
+[AC_LANG_PROGRAM([#include <unistd.h>
+#include <fcntl.h>],
+[return fcntl(0, F_DUPFD_CLOEXEC, 0)])],
+have_dupfd_cloexec=yes, have_dupfd_cloexec=no)
+AC_MSG_RESULT($have_dupfd_cloexec)
+if test "$have_dupfd_cloexec" = "yes"; then
+ AC_DEFINE([HAVE_F_DUPFD_CLOEXEC], [1],
+ [Define if your system supports F_DUPFD_CLOEXEC])
+fi
+
AC_ARG_WITH(libedit, AS_HELP_STRING(--with-libedit, [Compile with libedit support]))
use_libedit=
if test "$with_libedit" = "yes"; then
diff --git a/src/redir.c b/src/redir.c
index 5a5835c..c923bfa 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -446,14 +446,21 @@ savefd(int from, int ofd)
int newfd;
int err;
+#if HAVE_F_DUPFD_CLOEXEC
+ newfd = fcntl(from, F_DUPFD_CLOEXEC, 10);
+#else
newfd = fcntl(from, F_DUPFD, 10);
+#endif
+
err = newfd < 0 ? errno : 0;
if (err != EBADF) {
close(ofd);
if (err)
sh_error("%d: %s", from, strerror(err));
+#if !HAVE_F_DUPFD_CLOEXEC
else
fcntl(newfd, F_SETFD, FD_CLOEXEC);
+#endif
}
return newfd;
--
2.30.2
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