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gmem.h: Use __typeof__() in the g_clear_pointer() macro

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Type punning is used on the existing implementation, which hides errors
such as:

  GSList *list = NULL;
  g_clear_pointer (&list, g_error_free);

Let's use __typeof__ to cast the passed-in pointer before it's passed to
the free function so it trips -Wincompatible-pointer-types if it's wrong.

Fixes #1425
This commit is contained in:
Iain Lane 2018-07-10 15:48:58 +01:00
parent 2aacef39b1
commit f9a9902aac
2 changed files with 28 additions and 0 deletions
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11
glib/gmem.h
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@ -110,6 +110,16 @@ gpointer g_try_realloc_n (gpointer mem,
gsize n_blocks,
gsize n_block_bytes) G_GNUC_WARN_UNUSED_RESULT;
#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)) && !defined(__cplusplus) && GLIB_VERSION_MAX_ALLOWED >= GLIB_VERSION_2_58
#define g_clear_pointer(pp, destroy) \
G_STMT_START { \
G_STATIC_ASSERT (sizeof *(pp) == sizeof (gpointer)); \
__typeof__(*(pp)) _ptr = *(pp); \
*(pp) = NULL; \
if (_ptr) \
(destroy) (_ptr); \
} G_STMT_END
#else /* __GNUC__ */
#define g_clear_pointer(pp, destroy) \
G_STMT_START { \
G_STATIC_ASSERT (sizeof *(pp) == sizeof (gpointer)); \
@ -127,6 +137,7 @@ gpointer g_try_realloc_n (gpointer mem,
_destroy (_p); \
} \
} G_STMT_END
#endif /* __GNUC__ */
/**
* g_steal_pointer:

17
glib/tests/utils.c
View File

@ -517,6 +517,22 @@ test_clear_pointer (void)
g_assert (a == NULL);
}
/* Test that g_clear_pointer() works with a GDestroyNotify which contains a cast.
* See https://gitlab.gnome.org/GNOME/glib/issues/1425 */
static void
test_clear_pointer_cast (void)
{
GHashTable *hash_table = NULL;
hash_table = g_hash_table_new (g_str_hash, g_str_equal);
g_assert_nonnull (hash_table);
g_clear_pointer (&hash_table, (void (*) (GHashTable *)) g_hash_table_destroy);
g_assert_null (hash_table);
}
static int obj_count;
static void
@ -656,6 +672,7 @@ main (int argc,
g_test_add_func ("/utils/specialdir", test_special_dir);
g_test_add_func ("/utils/specialdir/desktop", test_desktop_special_dir);
g_test_add_func ("/utils/clear-pointer", test_clear_pointer);
g_test_add_func ("/utils/clear-pointer-cast", test_clear_pointer_cast);
g_test_add_func ("/utils/take-pointer", test_take_pointer);
g_test_add_func ("/utils/clear-source", test_clear_source);
g_test_add_func ("/utils/misc-mem", test_misc_mem);