X-Git-Url: https://git.distorted.org.uk/~mdw/sod/blobdiff_plain/7d21069e791a4d164c1eb1fc4f1ae661fe08ffbe..2b2252cc8d730004a1c95f227a0024a28b65087c:/lib/sod.h

diff --git a/lib/sod.h b/lib/sod.h
index 594e343..360afa8 100644
--- a/lib/sod.h
+++ b/lib/sod.h
@@ -7,7 +7,7 @@
 
 /*----- Licensing notice --------------------------------------------------*
  *
- * This file is part of the Sensble Object Design, an object system for C.
+ * This file is part of the Sensible Object Design, an object system for C.
  *
  * The SOD Runtime Library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public License as
@@ -32,6 +32,63 @@
   extern "C" {
 #endif
 
+/*----- Preliminary utilities ---------------------------------------------*/
+
+/* --- @SOD__HAVE_VARARGS_MACROS@ --- *
+ *
+ * Use:		Defined if the compiler supports C99-style variadic macros.
+ *
+ *		This is more complicated than just checking the value of
+ *		@__STDC_VERSION__@ because GCC has traditionally claimed C89
+ *		by default, but provides the functionality anyway unless it's
+ *		been explicitly turned off.
+ */
+
+#if __STDC_VERSION__ >= 199901
+   /* The feature exists.  All is well with the world. */
+
+#  define SOD__HAVE_VARARGS_MACROS
+
+#elif __GNUC__ >= 3
+   /* We're using GCC, which is trying to deny it but we don't believe it.
+    * Unfortunately there's a fly in the ointment: if `-pedantic' -- or,
+    * worse, `-pedantic-errors' -- is set, then GCC will warn about these
+    * macros being defined, and there isn't a way to detect pedantry from the
+    * preprocessor.
+    *
+    * We must deploy bodges.  There doesn't seem to be a good way to suppress
+    * particular warnings from the preprocessor: in particular, messing about
+    * with `pragma GCC diagnostic' doesn't help.  So we're left with this
+    * hack: just declare all Sod-generated header files which try to do
+    * varargs macro things to be `system headers', which means that GCC's
+    * preprocessor will let them get away with all manner of nefarious stuff.
+    */
+
+#  define SOD__HAVE_VARARGS_MACROS
+#  define SOD__VARARGS_MACROS_PREAMBLE _Pragma("GCC system_header")
+
+#endif
+
+/* Make sure this gratuitous hack is understood, at least vacuously. */
+#ifndef SOD__VARARGS_MACROS_PREAMBLE
+#  define SOD__VARARGS_MACROS_PREAMBLE
+#endif
+
+/* We're going to want to make use of this ourselves. */
+SOD__VARARGS_MACROS_PREAMBLE
+
+/* --- @SOD__CAR@ --- *
+ *
+ * Arguments:	@...@ = a nonempty list of arguments
+ *
+ * Returns:	The first argument only.
+ */
+
+#ifdef SOD__HAVE_VARARGS_MACROS
+#  define SOD__CAR(...) SOD__CARx(__VA_LIST__, _)
+#  define SOD__CARx(a, ...) a
+#endif
+
 /*----- Header files ------------------------------------------------------*/
 
 #include <stdarg.h>
@@ -53,7 +110,7 @@ struct sod_vtable {
  * these.
  */
 struct sod_instance {
-  struct sod_vtable *_vt;		/* Pointer to (chain's) vtable */
+  const struct sod_vtable *_vt;		/* Pointer to (chain's) vtable */
 };
 
 /* Information about a particular chain of superclasses.  In each class,
@@ -76,14 +133,15 @@ struct sod_chain {
  * Arguments:	@chead@ = nickname of target chain's head
  *		@obj@ = pointer to an instance chain
  *
- * Returns:	Pointer to target chain, as a @char *@.
+ * Returns:	Pointer to target chain, as a @void *@.
  *
  * Use:		Utility for implementing cross-chain upcasts.  It's probably
  *		not that clever to use this macro directly; it's used to make
  *		the automatically-generated upcast macros more palatable.
  */
 
-#define SOD_XCHAIN(chead, obj) ((char *)(obj) + (obj)->_vt->_off_##chead)
+#define SOD_XCHAIN(chead, obj)						\
+  ((void *)((char *)(obj) + (obj)->_vt->_off_##chead))
 
 /* --- @SOD_OFFSETDIFF@ --- *
  *
@@ -130,7 +188,7 @@ struct sod_chain {
  *
  * Arguments:	@p@ = pointer to an instance chain
  *
- * Returns:	A pointer to the instance's class, as a const SodClass.
+ * Returns:	A pointer to the instance's class, as a @const SodClass *@.
  */
 
 #define SOD_CLASSOF(obj) ((const SodClass *)(obj)->_vt->_class)
@@ -168,6 +226,19 @@ struct sod_chain {
 
 #define SOD_CONVERT(cls, obj) ((cls *)sod_convert(cls##__class, (obj)))
 
+/* --- @SOD_DECL@ --- *
+ *
+ * Arguments:	@cls_@ = a class type name
+ *		@var_@ = a variable name
+ *
+ * Use:		Declare @var_@ as a pointer to an initialized instance of
+ *		@cls_@ with automatic lifetime.
+ */
+
+#define SOD_DECL(cls_, var_)						\
+  struct cls_##__ilayout var_##__layout;				\
+  cls_ *var_ = cls_##__class->cls.init(&var_##__layout)
+
 /*----- Functions provided ------------------------------------------------*/
 
 /* --- @sod_subclassp@ --- *