Merge branch 'mr/issue-1575' into 'master'

Enable compile time check of g_date_time_format() format

See merge request GNOME/glib!412

docs/reference/glib/glib-sections.txt

@@ -442,6 +442,7 @@ G_GNUC_FALLTHROUGH
 G_GNUC_UNUSED
 G_GNUC_PRINTF
 G_GNUC_SCANF
+G_GNUC_STRFTIME
 G_GNUC_FORMAT
 G_GNUC_NULL_TERMINATED
 G_GNUC_WARN_UNUSED_RESULT

glib/docs.c

@@ -2359,6 +2359,23 @@
  * for details.
  */
 
+/**
+ * G_GNUC_STRFTIME:
+ * @format_idx: the index of the argument corresponding to
+ *     the format string (the arguments are numbered from 1)
+ *
+ * Expands to the GNU C strftime format function attribute if the compiler
+ * is gcc. This is used for declaring functions which take a format argument
+ * which is passed to strftime() or an API implementing its formats. It allows
+ * the compiler check the format passed to the function.
+ *
+ * See the
+ * [GNU C documentation](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-Wformat-3288)
+ * for details.
+ *
+ * Since: 2.60
+ */
+
 /**
  * G_GNUC_FORMAT:
  * @arg_idx: the index of the argument

glib/gdatetime.h

@@ -261,7 +261,7 @@ GDateTime *             g_date_time_to_utc                              (GDateTi
 
 GLIB_AVAILABLE_IN_ALL
 gchar *                 g_date_time_format                              (GDateTime      *datetime,
-                                                                         const gchar    *format) G_GNUC_MALLOC;
+                                                                         const gchar    *format) G_GNUC_MALLOC G_GNUC_STRFTIME (2);
 
 G_END_DECLS
 

glib/gmacros.h

@@ -165,11 +165,15 @@
   __attribute__((__format__ (gnu_printf, format_idx, arg_idx)))
 #define G_GNUC_SCANF( format_idx, arg_idx )     \
   __attribute__((__format__ (gnu_scanf, format_idx, arg_idx)))
+#define G_GNUC_STRFTIME( format_idx )    \
+  __attribute__((__format__ (gnu_strftime, format_idx, 0)))
 #else
 #define G_GNUC_PRINTF( format_idx, arg_idx )    \
   __attribute__((__format__ (__printf__, format_idx, arg_idx)))
 #define G_GNUC_SCANF( format_idx, arg_idx )     \
   __attribute__((__format__ (__scanf__, format_idx, arg_idx)))
+#define G_GNUC_STRFTIME( format_idx )    \
+  __attribute__((__format__ (__strftime__, format_idx, 0)))
 #endif
 #define G_GNUC_FORMAT( arg_idx )                \
   __attribute__((__format_arg__ (arg_idx)))
@@ -184,6 +188,7 @@
 #else   /* !__GNUC__ */
 #define G_GNUC_PRINTF( format_idx, arg_idx )
 #define G_GNUC_SCANF( format_idx, arg_idx )
+#define G_GNUC_STRFTIME( format_idx )
 #define G_GNUC_FORMAT( arg_idx )
 #define G_GNUC_NORETURN
 #define G_GNUC_CONST

glib/tests/gdatetime.c

@@ -25,6 +25,14 @@
 #include <glib/gstdio.h>
 #include <locale.h>
 
+/* The tests below exercise invalid formats and y2k-unsafe formats,
+ * so we need to silence the warnings here to pass.
+ */
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-Wformat"
+#pragma GCC diagnostic ignored "-Wformat-y2k"
+#endif
+
 #define ASSERT_DATE(dt,y,m,d) G_STMT_START { \
   g_assert_nonnull ((dt)); \
   g_assert_cmpint ((y), ==, g_date_time_get_year ((dt))); \

tests/datetime.c

@@ -18,6 +18,14 @@
 #include <locale.h>
 #include <glib/glib.h>
 
+/* The whole purpose of this test is to pass the command line argument
+ * to g_date_time_format(), so the format argument cannot be compile-
+ * time checked. Disable the inevitable compiler warning.
+ */
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+#endif
+
 int
 main (int argc, char *argv[])
 {