Add feature test APIs to libobjc2.

GNUmakefile

@@ -17,6 +17,7 @@ libobjc_OBJC_FILES = \
 
 libobjc_C_FILES = \
 	abi_version.c\
+	caps.c\
 	category_loader.c\
 	class_table.c\
 	dtable.c\
@@ -43,6 +44,7 @@ ifneq ($(install_headers), no)
 libobjc_HEADER_FILES = \
 	Availability.h\
 	blocks_runtime.h\
+	capabilities.h\
 	hooks.h\
 	runtime.h\
 	slot.h\

caps.c

@@ -0,0 +1,28 @@
+#include "objc/capabilities.h"
+#include <stdint.h>
+
+/**
+ * Bitmask of all of the capabilities compiled into this version of the
+ * runtime.
+ */
+static const int32_t caps =
+	(1<<OBJC_CAP_EXCEPTIONS) |
+	(1<<OBJC_CAP_SYNCRONIZE) |
+	(1<<OBJC_CAP_PROPERTIES) |
+	(1<<OBJC_CAP_PROPERTY_INTROSPECTION) |
+	(1<<OBJC_CAP_OPTIONAL_PROTOCOLS) |
+	(1<<OBJC_CAP_NONFRAGILE_IVARS) |
+#ifdef TYPE_DEPENDENT_DISPATCH
+	(1<<OBJC_CAP_TYPE_DEPENDENT_DISPATCH) |
+#endif
+#ifdef __OBJC_LOW_MEMORY__
+	(1<<OBJC_CAP_LOW_MEMORY) |
+#endif
+	0;
+
+int objc_test_capability(int x)
+{
+	if (x >= 32) { return 0; }
+	if (caps & (1<<x)) { return 1; }
+	return 0;
+}

objc/capabilities.h

@@ -0,0 +1,71 @@
+/**
+ * capabilities.h - This file defines the list of capabilities.  Runtime
+ * capabilities can be checked.  You may use #ifdef to test at compile time
+ * whether the runtime on the current platform understands the capability.
+ * This does not mean that the runtime implements the capability, however.  
+ *
+ * A copy of this file exists for compatibility in GNUstep's Objective-C
+ * framework.  When using this framework in conjunction with the GNU
+ * Objective-C runtime, most of the features will not be supported at run time,
+ * even if the corresponding macros are available at compile time.
+ * Additionally, several are compile-time options in the GNUstep runtime, so
+ * although they are present in the header and understood by the runtime, they
+ * may not be supported by the installed runtime.  
+ */
+
+/**
+ * The runtime supports zero-cost exceptions.  
+ */
+#define OBJC_CAP_EXCEPTIONS              0
+/**
+ * The runtime supports the @synchronize directive.
+ */
+#define OBJC_CAP_SYNCRONIZE              1
+/**
+ * The runtime supports property accessors.
+ */
+#define OBJC_CAP_PROPERTIES              2
+/**
+ * The runtime supports introspection on declared properties.
+ */
+#define OBJC_CAP_PROPERTY_INTROSPECTION  3
+/**
+ * The runtime supports optional methods and declared properties in protocols.
+ */
+#define OBJC_CAP_OPTIONAL_PROTOCOLS      4
+/**
+ * The runtime supports non-fragile instance variables.  
+ */
+#define OBJC_CAP_NONFRAGILE_IVARS        5
+/**
+ * The runtime supports making method lookup dependent on the types, as well as
+ * the name, of the selector.  
+ */
+#define OBJC_CAP_TYPE_DEPENDENT_DISPATCH 6
+/**
+ * The runtime was compiled in the low-memory profile.  This trades some speed
+ * for reduced memory consumption.
+ */
+#define OBJC_CAP_LOW_MEMORY              7
+
+
+/**
+ * Macro used to require the existence of a specific capability.  This creates
+ * a function that is called by the loader and tests that the runtime supports
+ * the required capability, aborting if it does not.
+ */
+#define OBJC_REQUIRE_CAPABILITY(x) \
+	__attribute__((constructor)) static void objc_test ## x(void)\
+	{\
+		if (!objc_test_capability(x))\
+		{\
+			fprintf(stderr, "Runtime does not support required property: " #x "\n");\
+			exit(1);\
+		}\
+	}
+
+/**
+ * Run time feature test.  This function returns 1 if the runtime supports the
+ * specified feature or 0 if it does not.
+ */
+int objc_test_capability(int x);