backports: Add g_steal_fd, from GLib >= 2.70

This is essentially the same as glnx_steal_fd, so make glnx_steal_fd an
alias for it.

The unit test is taken from GLib, slightly modified to avoid g_close()
and also test the old name glnx_steal_fd().

Signed-off-by: Simon McVittie <smcv@collabora.com>

6 files changed, 62 insertions, 15 deletions

diff --git a/glnx-backports.h b/glnx-backports.h
index f99f08f..ad70ed9 100644
--- a/glnx-backports.h
+++ b/glnx-backports.h
@@ -118,6 +118,17 @@ _glnx_memdup2 (gconstpointer mem,
   (((a) > (b) ? (a) - (b) : (b) - (a)) < (epsilon))
 #endif
 
+#if !GLIB_CHECK_VERSION(2, 70, 0)
+#define g_steal_fd _glnx_steal_fd
+static inline int
+_glnx_steal_fd (int *fdp)
+{
+  int fd = *fdp;
+  *fdp = -1;
+  return fd;
+}
+#endif
+
 #if !GLIB_CHECK_VERSION(2, 74, 0)
 #define G_APPLICATION_DEFAULT_FLAGS ((GApplicationFlags) 0)
 #define G_CONNECT_DEFAULT ((GConnectFlags) 0)
diff --git a/glnx-dirfd.c b/glnx-dirfd.c
index b039c41..b78e2df 100644
--- a/glnx-dirfd.c
+++ b/glnx-dirfd.c
@@ -129,7 +129,7 @@ glnx_dirfd_iterator_init_take_fd (int               *dfd,
   if (!d)
     return glnx_throw_errno_prefix (error, "fdopendir");
 
-  real_dfd_iter->fd = glnx_steal_fd (dfd);
+  real_dfd_iter->fd = g_steal_fd (dfd);
   real_dfd_iter->d = d;
   real_dfd_iter->initialized = TRUE;
 
@@ -349,7 +349,7 @@ glnx_mkdtempat (int dfd, const char *tmpl, int mode,
       /* Return the initialized directory struct */
       out_tmpdir->initialized = TRUE;
       out_tmpdir->src_dfd = dfd; /* referenced; see above docs */
-      out_tmpdir->fd = glnx_steal_fd (&ret_dfd);
+      out_tmpdir->fd = g_steal_fd (&ret_dfd);
       out_tmpdir->path = g_steal_pointer (&path);
       return TRUE;
     }
diff --git a/glnx-fdio.c b/glnx-fdio.c
index b1af679..9873205 100644
--- a/glnx-fdio.c
+++ b/glnx-fdio.c
@@ -218,7 +218,7 @@ open_tmpfile_core (int dfd, const char *subpath,
           return glnx_throw_errno_prefix (error, "fchmod");
         out_tmpf->initialized = TRUE;
         out_tmpf->src_dfd = dfd; /* Copied; caller must keep open */
-        out_tmpf->fd = glnx_steal_fd (&fd);
+        out_tmpf->fd = g_steal_fd (&fd);
         out_tmpf->path = NULL;
         return TRUE;
       }
@@ -245,7 +245,7 @@ open_tmpfile_core (int dfd, const char *subpath,
           {
             out_tmpf->initialized = TRUE;
             out_tmpf->src_dfd = dfd;  /* Copied; caller must keep open */
-            out_tmpf->fd = glnx_steal_fd (&fd);
+            out_tmpf->fd = g_steal_fd (&fd);
             out_tmpf->path = g_steal_pointer (&tmp);
             return TRUE;
           }
@@ -463,7 +463,7 @@ glnx_tmpfile_reopen_rdonly (GLnxTmpfile *tmpf,
     }
 
   glnx_close_fd (&tmpf->fd);
-  tmpf->fd = glnx_steal_fd (&rdonly_fd);
+  tmpf->fd = g_steal_fd (&rdonly_fd);
   return TRUE;
 }
 
diff --git a/glnx-local-alloc.h b/glnx-local-alloc.h
index 615b954..65ae747 100644
--- a/glnx-local-alloc.h
+++ b/glnx-local-alloc.h
@@ -24,6 +24,8 @@
 #include <gio/gio.h>
 #include <errno.h>
 
+#include "glnx-backports.h"
+
 G_BEGIN_DECLS
 
 /**
@@ -43,19 +45,14 @@ glnx_local_obj_unref (void *v)
 }
 #define glnx_unref_object __attribute__ ((cleanup(glnx_local_obj_unref)))
 
-static inline int
-glnx_steal_fd (int *fdp)
-{
-  int fd = *fdp;
-  *fdp = -1;
-  return fd;
-}
+/* Backwards-compat with older libglnx */
+#define glnx_steal_fd g_steal_fd
 
 /**
  * glnx_close_fd:
  * @fdp: Pointer to fd
  *
- * Effectively `close (glnx_steal_fd (&fd))`.  Also
+ * Effectively `close (g_steal_fd (&fd))`.  Also
  * asserts that `close()` did not raise `EBADF` - encountering
  * that error is usually a critical bug in the program.
  */
@@ -66,7 +63,7 @@ glnx_close_fd (int *fdp)
 
   g_assert (fdp);
 
-  int fd = glnx_steal_fd (fdp);
+  int fd = g_steal_fd (fdp);
   if (fd >= 0)
     {
       errsv = errno;
diff --git a/glnx-lockfile.c b/glnx-lockfile.c
index 65a1558..fcda84c 100644
--- a/glnx-lockfile.c
+++ b/glnx-lockfile.c
@@ -129,7 +129,7 @@ glnx_make_lock_file(int dfd, const char *p, int operation, GLnxLockFile *out_loc
         out_lock->initialized = TRUE;
         out_lock->dfd = dfd;
         out_lock->path = g_steal_pointer (&t);
-        out_lock->fd = glnx_steal_fd (&fd);
+        out_lock->fd = g_steal_fd (&fd);
         out_lock->operation = operation;
         return TRUE;
 }
diff --git a/tests/test-libglnx-backports.c b/tests/test-libglnx-backports.c
index c475cd4..0fa374e 100644
--- a/tests/test-libglnx-backports.c
+++ b/tests/test-libglnx-backports.c
@@ -2,12 +2,15 @@
  *
  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
  * Copyright 2019 Emmanuel Fleury
+ * Copyright 2021 Collabora Ltd.
  * SPDX-License-Identifier: LGPL-2.1-or-later AND LicenseRef-old-glib-tests
  */
 
 #include "libglnx-config.h"
 #include "libglnx.h"
 
+#include <glib/gstdio.h>
+
 /* Testing g_memdup2() function with various positive and negative cases */
 static void
 test_memdup2 (void)
@@ -28,9 +31,45 @@ test_memdup2 (void)
   g_free (str_dup);
 }
 
+static void
+test_steal_fd (void)
+{
+  GError *error = NULL;
+  gchar *tmpfile = NULL;
+  int fd = -42;
+  int borrowed;
+  int stolen;
+
+  g_assert_cmpint (g_steal_fd (&fd), ==, -42);
+  g_assert_cmpint (fd, ==, -1);
+  g_assert_cmpint (g_steal_fd (&fd), ==, -1);
+  g_assert_cmpint (fd, ==, -1);
+
+  fd = g_file_open_tmp (NULL, &tmpfile, &error);
+  g_assert_cmpint (fd, >=, 0);
+  g_assert_no_error (error);
+  borrowed = fd;
+  stolen = g_steal_fd (&fd);
+  g_assert_cmpint (fd, ==, -1);
+  g_assert_cmpint (borrowed, ==, stolen);
+
+  g_assert_no_errno (close (g_steal_fd (&stolen)));
+  g_assert_cmpint (stolen, ==, -1);
+
+  g_assert_no_errno (remove (tmpfile));
+  g_free (tmpfile);
+
+  /* Backwards compatibility with older libglnx: glnx_steal_fd is the same
+   * as g_steal_fd */
+  fd = -23;
+  g_assert_cmpint (glnx_steal_fd (&fd), ==, -23);
+  g_assert_cmpint (fd, ==, -1);
+}
+
 int main (int argc, char **argv)
 {
   g_test_init (&argc, &argv, NULL);
+  g_test_add_func ("/mainloop/steal-fd", test_steal_fd);
   g_test_add_func ("/strfuncs/memdup2", test_memdup2);
   return g_test_run();
 }