Merge remote-tracking branch 'jeremyhu/master'

4 files changed, 23 insertions, 6 deletions

diff --git a/configure.ac b/configure.ac
index abfe72766..ab890273f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -137,6 +137,7 @@ AC_CHECK_HEADERS([fcntl.h stdlib.h string.h unistd.h dlfcn.h stropts.h fnmatch.h
 
 dnl Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST
+AC_C_TYPEOF
 AC_C_BIGENDIAN([ENDIAN="X_BIG_ENDIAN"], [ENDIAN="X_LITTLE_ENDIAN"])
 
 AC_CHECK_SIZEOF([unsigned long])
diff --git a/include/dix-config.h.in b/include/dix-config.h.in
index 77681a953..578f249b3 100644
--- a/include/dix-config.h.in
+++ b/include/dix-config.h.in
@@ -423,6 +423,9 @@
 /* Define to 64-bit byteswap macro */
 #undef bswap_64
 
+/* Define to 1 if typeof works with your compiler. */
+#undef HAVE_TYPEOF
+
 /* The compiler supported TLS storage class, prefering initial-exec if tls_model is supported */
 #undef TLS
 
diff --git a/include/list.h b/include/list.h
index d54a207b1..2d48a8646 100644
--- a/include/list.h
+++ b/include/list.h
@@ -26,6 +26,8 @@
 #ifndef _XORG_LIST_H_
 #define _XORG_LIST_H_
 
+#include <stddef.h> /* offsetof() */
+
 /**
  * @file Classic doubly-link circular list implementation.
  * For real usage examples of the linked list, see the file test/list.c
@@ -232,7 +234,7 @@ xorg_list_is_empty(struct xorg_list *head)
  */
 #ifndef container_of
 #define container_of(ptr, type, member) \
-    (type *)((char *)(ptr) - (char *) &((type *)0)->member)
+    (type *)((char *)(ptr) - offsetof(type, member))
 #endif
 
 /**
@@ -271,9 +273,20 @@ xorg_list_is_empty(struct xorg_list *head)
 #define xorg_list_last_entry(ptr, type, member) \
     xorg_list_entry((ptr)->prev, type, member)
 
-#define __container_of(ptr, sample, member)				\
-    (void *)((char *)(ptr)						\
-	     - ((char *)&(sample)->member - (char *)(sample)))
+#ifdef HAVE_TYPEOF
+#define __container_of(ptr, sample, member)			\
+    container_of(ptr, typeof(*sample), member)
+#else
+/* This implementation of __container_of has undefined behavior according
+ * to the C standard, but it works in many cases.  If your compiler doesn't
+ * support typeof() and fails with this implementation, please try a newer
+ * compiler.
+ */
+#define __container_of(ptr, sample, member)                            \
+    (void *)((char *)(ptr)                                             \
+            - ((char *)&(sample)->member - (char *)(sample)))
+#endif
+
 /**
  * Loop through the list given by head and set pos to struct in the list.
  *
diff --git a/test/list.c b/test/list.c
index 82d232706..f9f54ee4e 100644
--- a/test/list.c
+++ b/test/list.c
@@ -137,7 +137,7 @@ static void
 test_xorg_list_del(void)
 {
     struct parent parent = { 0 };
-    struct child child[3];
+    struct child child[2];
     struct child *c;
 
     xorg_list_init(&parent.children);
@@ -178,8 +178,8 @@ test_xorg_list_del(void)
     xorg_list_add(&child[0].node, &parent.children);
     xorg_list_del(&parent.children);
     assert(xorg_list_is_empty(&parent.children));
+    assert(!xorg_list_is_empty(&child[0].node));
     assert(!xorg_list_is_empty(&child[1].node));
-    assert(!xorg_list_is_empty(&child[2].node));
 }
 
 static void