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Merge branch 'wip/smcv/autofd' into 'main'
gstdio: Add g_clear_fd() and g_autofd See merge request GNOME/glib!3007
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commit
2ae9c405df
@ -1454,6 +1454,8 @@ g_creat
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g_chdir
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g_utime
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g_close
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g_clear_fd
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g_autofd
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<SUBSECTION Private>
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g_file_error_quark
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@ -1276,7 +1276,7 @@
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#if g_macro__has_attribute(cleanup)
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/* these macros are private */
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/* these macros are private; note that gstdio.h also uses _GLIB_CLEANUP */
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#define _GLIB_AUTOPTR_FUNC_NAME(TypeName) glib_autoptr_cleanup_##TypeName
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#define _GLIB_AUTOPTR_CLEAR_FUNC_NAME(TypeName) glib_autoptr_clear_##TypeName
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#define _GLIB_AUTOPTR_TYPENAME(TypeName) TypeName##_autoptr
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100
glib/gstdio.c
100
glib/gstdio.c
@ -1837,3 +1837,103 @@ g_close (gint fd,
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return TRUE;
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}
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/**
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* g_clear_fd: (skip)
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* @fd_ptr: (not nullable): a pointer to a file descriptor
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* @error: Used to return an error on failure
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*
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* If @fd_ptr points to a file descriptor, close it and return
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* whether closing it was successful, like g_close().
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* If @fd_ptr points to a negative number, return %TRUE without closing
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* anything.
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* In both cases, set @fd_ptr to `-1` before returning.
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*
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* It is a programming error for @fd_ptr to point to a non-negative
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* number that is not a valid file descriptor.
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*
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* A typical use of this function is to clean up a file descriptor at
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* the end of its scope, whether it has been set successfully or not:
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*
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* |[
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* gboolean
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* operate_on_fd (GError **error)
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* {
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* gboolean ret = FALSE;
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* int fd = -1;
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*
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* fd = open_a_fd (error);
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*
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* if (fd < 0)
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* goto out;
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*
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* if (!do_something (fd, error))
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* goto out;
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*
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* if (!g_clear_fd (&fd, error))
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* goto out;
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*
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* ret = TRUE;
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*
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* out:
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* // OK to call even if fd was never opened or was already closed
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* g_clear_fd (&fd, NULL);
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* return ret;
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* }
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* ]|
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*
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* This function is also useful in conjunction with #g_autofd.
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*
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* Returns: %TRUE on success
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* Since: 2.76
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*/
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/**
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* g_autofd: (skip)
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*
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* Macro to add an attribute to a file descriptor variable to ensure
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* automatic cleanup using g_clear_fd().
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*
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* This macro behaves like #g_autofree rather than g_autoptr(): it is
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* an attribute supplied before the type name, rather than wrapping the
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* type definition.
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*
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* Otherwise, this macro has similar constraints as g_autoptr(): it is
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* only supported on GCC and clang, and the variable must be initialized
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* (to either a valid file descriptor or a negative number).
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*
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* Any error from closing the file descriptor when it goes out of scope
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* is ignored. Use g_clear_fd() if error-checking is required.
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*
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* |[
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* gboolean
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* operate_on_fds (GError **error)
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* {
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* g_autofd int fd1 = open_a_fd (..., error);
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* g_autofd int fd2 = -1;
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*
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* // it is safe to return early here, nothing will be closed
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* if (fd1 < 0)
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* return FALSE;
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*
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* fd2 = open_a_fd (..., error);
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*
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* // fd1 will be closed automatically if we return here
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* if (fd2 < 0)
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* return FALSE;
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*
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* // fd1 and fd2 will be closed automatically if we return here
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* if (!do_something_useful (fd1, fd2, error))
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* return FALSE;
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*
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* // fd2 will be closed automatically if we return here
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* if (!g_clear_fd (&fd1, error))
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* return FALSE;
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*
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* // fd2 will be automatically closed here if still open
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* return TRUE;
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* }
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* ]|
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*
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* Since: 2.76
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*/
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@ -178,6 +178,38 @@ GLIB_AVAILABLE_IN_2_36
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gboolean g_close (gint fd,
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GError **error);
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GLIB_AVAILABLE_STATIC_INLINE_IN_2_76
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static inline gboolean
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g_clear_fd (int *fd_ptr,
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GError **error)
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{
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int fd = *fd_ptr;
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*fd_ptr = -1;
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if (fd < 0)
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return TRUE;
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return g_close (fd, error);
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}
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/* g_autofd should be defined on the same compilers where g_autofree is
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* This avoids duplicating the feature-detection here. */
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#ifdef g_autofree
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/* Not public API */
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static inline void
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_g_clear_fd_ignore_error (int *fd_ptr)
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{
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if (!g_clear_fd (fd_ptr, NULL))
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{
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/* Do nothing: we ignore all errors, except for EBADF which
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* is a programming error, checked for by g_close(). */
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}
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}
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#define g_autofd _GLIB_CLEANUP(_g_clear_fd_ignore_error)
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#endif
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G_END_DECLS
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#endif /* __G_STDIO_H__ */
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@ -2453,6 +2453,81 @@ test_win32_zero_terminate_symlink (void)
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#endif
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static void
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assert_fd_was_closed (int fd)
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{
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/* We can't tell a fd was really closed without behaving as though it
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* was still valid */
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if (g_test_undefined ())
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{
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int result = g_fsync (fd);
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int errsv = errno;
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g_assert_cmpint (result, !=, 0);
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g_assert_cmpint (errsv, ==, EBADF);
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}
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}
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static void
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test_clear_fd (void)
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{
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char *name = NULL;
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GError *error = NULL;
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int fd;
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int copy_of_fd;
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#ifdef g_autofree
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g_test_summary ("Test g_clear_fd() and g_autofd");
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#else
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g_test_summary ("Test g_clear_fd() (g_autofd unsupported by this compiler)");
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#endif
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/* g_clear_fd() normalizes any negative number to -1 */
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fd = -23;
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g_clear_fd (&fd, &error);
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g_assert_cmpint (fd, ==, -1);
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g_assert_no_error (error);
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/* Nothing special about g_file_open_tmp, it's just a convenient way
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* to get an open fd */
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fd = g_file_open_tmp (NULL, &name, &error);
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g_assert_cmpint (fd, !=, -1);
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g_assert_no_error (error);
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g_assert_nonnull (name);
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copy_of_fd = fd;
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g_clear_fd (&fd, &error);
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g_assert_cmpint (fd, ==, -1);
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g_assert_no_error (error);
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assert_fd_was_closed (copy_of_fd);
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g_unlink (name);
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g_free (name);
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/* g_clear_fd() is idempotent */
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g_clear_fd (&fd, &error);
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g_assert_cmpint (fd, ==, -1);
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g_assert_no_error (error);
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#ifdef g_autofree
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fd = g_file_open_tmp (NULL, &name, &error);
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g_assert_cmpint (fd, !=, -1);
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g_assert_no_error (error);
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g_assert_nonnull (name);
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{
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g_autofd int close_me = fd;
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g_autofd int was_never_set = -42;
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/* This avoids clang warnings about the variables being unused */
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g_test_message ("Will be closed by autocleanup: %d, %d",
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close_me, was_never_set);
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}
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assert_fd_was_closed (fd);
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g_unlink (name);
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g_free (name);
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#endif
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}
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int
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main (int argc,
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char *argv[])
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@ -2489,6 +2564,7 @@ main (int argc,
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g_test_add_func ("/fileutils/read-link", test_read_link);
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g_test_add_func ("/fileutils/stdio-wrappers", test_stdio_wrappers);
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g_test_add_func ("/fileutils/fopen-modes", test_fopen_modes);
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g_test_add_func ("/fileutils/clear-fd", test_clear_fd);
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return g_test_run ();
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}
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