Weak-import more symbols in closure_blocks_leopard_compat

chrome/browser/mac/closure_blocks_leopard_compat.h

Index: chrome/browser/mac/closure_blocks_leopard_compat.h
===================================================================
--- chrome/browser/mac/closure_blocks_leopard_compat.h	(revision 96949)
+++ chrome/browser/mac/closure_blocks_leopard_compat.h	(working copy)
@@ -61,6 +61,13 @@
 
 #include <AvailabilityMacros.h>
 
+#if defined(MAC_OS_X_VERSION_10_6) && \
+    MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_6  // SDK >= 10.6
+// Get the system's own declarations of these things if using an SDK where
+// they are present.
+#include <Block.h>
+#endif  // SDK >= 10.6
+
 extern "C" {
 
 #if MAC_OS_X_VERSION_MIN_REQUIRED <= MAC_OS_X_VERSION_10_5  // DT <= 10.5
@@ -69,6 +76,13 @@
 #define MAYBE_WEAK_IMPORT
 #endif  // DT <= 10.5
 
+MAYBE_WEAK_IMPORT extern void* _Block_copy(const void*);
+MAYBE_WEAK_IMPORT extern void _Block_release(const void*);
+MAYBE_WEAK_IMPORT extern void _Block_object_assign(void*,
+                                                   const void*,
+                                                   const int);
+MAYBE_WEAK_IMPORT extern void _Block_object_dispose(const void*, const int);

[Nico, 2011/08/16 17:18:14]

since you declare these here, why do you need the delcaration in the .S as well?

[Mark Mentovai, 2011/08/16 17:54:07]

Nico wrote:
These are declarations. The .S file has definitions.

The .h and .S files do two different, but related, things.

The declarations are necessary to tell anything that references these symbols
that they’re supposed to be weakly imported. Weak-import is a property of the
thing that references the symbol, not a property of the thing that defines the
symbol. The .h is needed when targeting 10.5, even if a newer SDK is in use, to
get the references to the symbols marked as weak imports.

The .S file exists to provide definitions so that the linker is able to resolve
the symbols. There’s some added magic to make it appear that the definitions
came from libSystem, so that dyld will look in libSystem for them at load time.
The .S is only needed when using the 10.5 SDK. Otherwise, the SDK’s libSystem
already has definitions.

+
 MAYBE_WEAK_IMPORT extern void* _NSConcreteGlobalBlock[32];
 MAYBE_WEAK_IMPORT extern void* _NSConcreteStackBlock[32];
 
@@ -76,4 +90,15 @@
 
 }  // extern "C"
 
+// Macros from <Block.h>, in case <Block.h> is not present.
+
+#ifndef Block_copy
+#define Block_copy(...) \
+    ((__typeof(__VA_ARGS__))_Block_copy((const void *)(__VA_ARGS__)))
+#endif
+
+#ifndef Block_release
+#define Block_release(...) _Block_release((const void *)(__VA_ARGS__))
+#endif
+
 #endif  // CHROME_BROWSER_MAC_CLOSURE_BLOCKS_LEOPARD_COMPAT_H_