Add offsetof macro for those without it.

diff --git a/include/missing.h b/include/missing.h
index 658f399da04f40941203d45c3070d9e3ac656be9..6f00a5760624b93c9d143f0b9988638e2e8be2eb 100644 (file)
--- a/include/missing.h
+++ b/include/missing.h
@@ -122,6 +122,17 @@
 # define MAX(a,b) (((a)>(b))?(a):(b))
 #endif
 
+/*
+ * Older systems may be missing stddef.h and/or offsetof macro
+ */
+#ifndef offsetof
+# ifdef __offsetof
+#  define offsetof(type, field) __offsetof(type, field)
+# else
+#  define offsetof(type, field) ((size_t)(&((type *)0)->field))
+# endif
+#endif
+
 /*
  * Simple isblank() macro and function for systems without it.
  */