object-file: move `git_open_cloexec()` to "compat/open.c"

The `git_open_cloexec()` wrapper function provides the ability to open a
file with `O_CLOEXEC` in a platform-agnostic way. This function is
provided by "object-file.c" even though it is not specific to the object
subsystem at all.

Move the file into "compat/open.c". This file already exists before this
commit, but has only been compiled conditionally depending on whether or
not open(3p) may return EINTR. With this change we now unconditionally
compile the object, but wrap `git_open_with_retry()` in an ifdef.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/compat/open.c b/compat/open.c
index eb3754a23b..37ae2b1aeb 100644
--- a/compat/open.c
+++ b/compat/open.c
@@ -1,5 +1,6 @@
 #include "git-compat-util.h"
 
+#ifdef OPEN_RETURNS_EINTR
 #undef open
 int git_open_with_retry(const char *path, int flags, ...)
 {
@@ -23,3 +24,31 @@ int git_open_with_retry(const char *path, int flags, ...)
 
 	return ret;
 }
+#endif
+
+int git_open_cloexec(const char *name, int flags)
+{
+	int fd;
+	static int o_cloexec = O_CLOEXEC;
+
+	fd = open(name, flags | o_cloexec);
+	if ((o_cloexec & O_CLOEXEC) && fd < 0 && errno == EINVAL) {
+		/* Try again w/o O_CLOEXEC: the kernel might not support it */
+		o_cloexec &= ~O_CLOEXEC;
+		fd = open(name, flags | o_cloexec);
+	}
+
+#if defined(F_GETFD) && defined(F_SETFD) && defined(FD_CLOEXEC)
+	{
+		static int fd_cloexec = FD_CLOEXEC;
+
+		if (!o_cloexec && 0 <= fd && fd_cloexec) {
+			/* Opened w/o O_CLOEXEC?  try with fcntl(2) to add it */
+			int flags = fcntl(fd, F_GETFD);
+			if (fcntl(fd, F_SETFD, flags | fd_cloexec))
+				fd_cloexec = 0;
+		}
+	}
+#endif
+	return fd;
+}