This patch fixes PR libobjc/49883. To fix it, I installed clang and tried out
what
happens if you compile Objective-C code using clang and targetting the GCC
runtime.
Unfortunately, the report was correct in that clang is producing incorrect code
and
abusing the higher bits of the class->info field to store some other
information. On
the good side, the fix I proposed in the discussion of PR libobjc/49883
actually works.
:-)
So, I applied that fix.
I also found that clang still emits calls to the objc_lookup_class() function,
so this
patch also adds that function back into the runtime to get code compiled with
clang
work.
Committed to trunk.
Thanks
PS: In case anyone wonders, I do want the GNU Objective-C Runtime to be usable
with
free, non-GCC Objective-C compilers. It should obviously work perfectly with
GCC, the
GNU compiler, which is its natural partner, but some people would like to use
it with
other free compilers and that seems a reasonable request. Refusing that
request just
provides an incentive to write and support other Objective-C runtimes, which is
a
waste of time and resources. ;-)
Index: init.c
===================================================================
--- init.c (revision 179711)
+++ init.c (working copy)
@@ -643,6 +643,15 @@
assert (CLS_ISMETA (class->class_pointer));
DEBUG_PRINTF (" installing class '%s'\n", class->name);
+ /* Workaround for a bug in clang: Clang may set flags other than
+ _CLS_CLASS and _CLS_META even when compiling for the
+ traditional ABI (version 8), confusing our runtime. Try to
+ wipe these flags out. */
+ if (CLS_ISCLASS (class))
+ __CLS_INFO (class) = _CLS_CLASS;
+ else
+ __CLS_INFO (class) = _CLS_META;
+
/* Initialize the subclass list to be NULL. In some cases it
isn't and this crashes the program. */
class->subclass_list = NULL;
Index: class.c
===================================================================
--- class.c (revision 179711)
+++ class.c (working copy)
@@ -764,6 +764,15 @@
return objc_get_class (name)->class_pointer;
}
+/* This is not used by GCC, but the clang compiler seems to use it
+ when targetting the GNU runtime. That's wrong, but we have it to
+ be compatible. */
+Class
+objc_lookup_class (const char *name)
+{
+ return objc_getClass (name);
+}
+
/* This is used when the implementation of a method changes. It goes
through all classes, looking for the ones that have these methods
(either method_a or method_b; method_b can be NULL), and reloads
Index: ChangeLog
===================================================================
--- ChangeLog (revision 179711)
+++ ChangeLog (working copy)
@@ -1,3 +1,18 @@
+2011-10-09 Nicola Pero <nicola.p...@meta-innovation.com>
+
+ PR libobjc/49883
+ * init.c (__objc_exec_class): Work around a bug in clang's code
+ generation. Clang sets the class->info field to values different
+ from 0x1 or 0x2 (the only allowed values in the traditional GNU
+ Objective-C runtime ABI) to store some additional information, but
+ this breaks backwards compatibility. Wipe out all the bits in the
+ fields other than the first two upon loading a class.
+
+2011-10-09 Nicola Pero <nicola.p...@meta-innovation.com>
+
+ * class.c (objc_lookup_class): Added back for compatibility with
+ clang which seems to emit calls to it.
+
2011-10-08 Richard Frith-Macdonald <r...@gnu.org>
Nicola Pero <nicola.p...@meta-innovation.com>
