[Linux-ia64] Fwd: Bug#129641: mozilla illegal instruction fault on IA64 (with a fix)

[Linux-ia64] Fwd: Bug#129641: mozilla illegal instruction fault on IA64 (with a fix)

[Matt Chapman]

It was suggested that I forward this here, for the benefit of others
porting mozilla and any other software that relies on the C++ ABI.

Matt


----- Forwarded message from Matt Chapman <matthewc@cse.unsw.edu.au> -----

Package: mozilla-browser
Version: 0.9.7-4
Severity: important

Symptoms: Installation of package fails with "Illegal instruction" fault from
regxpcom; mozilla dies similarly when executing JavaScript.

This seems to be because in recent versions of g++ - since 3.0.2 according to
the ChangeLog - class vtables are arrays of function descriptors (which are
(code address, gp value) pairs) rather than arrays of function pointers (which
are pointers to function descriptors).

The following fix does the trick for me (it's a little evil, but then this kind
of code is necessarily evil :)).

Cheers,
Matt


--- mozilla/xpcom/reflect/xptcall/src/md/unix/xptcinvoke_ffi.old	Sun Jan  6 11:03:05 2002
+++ mozilla/xpcom/reflect/xptcall/src/md/unix/xptcinvoke_ffi.cpp	Thu Jan 17 15:34:56 2002
@@ -83,8 +83,9 @@
         long offset;		/* offset to beginning of object */
         unsigned long rtti;	/* address of run-time type info */
 #endif
-        void (*methods[1]) ();	/* method table (variable length) */
+        unsigned long methods[1];	/* method table (variable length) */
     } *vtable = *(struct vtable **) that;
+    void (*method)();
     ffi_type **arg_types;
     void **args;
     ffi_status status;
@@ -102,6 +103,13 @@
     if (status != FFI_OK)
         return NS_ERROR_INVALID_ARG;
 
-    ffi_call (&cif, vtable->methods[methodIndex], &result, args);
+/* As of g++ 3.0.2, IA64 vtables contain function descriptors - matthewc@cse.unsw.edu.au */
+#if defined(__ia64) && __GNUC__ >= 3 && !(__GNUC__ = 3 && __GNUC_MINOR__ = 0 && __GNUC_PATCHLEVEL__ < 2)
+    method = (void (*)())&vtable->methods[2*methodIndex];
+#else
+    method = (void (*)())vtable->methods[methodIndex];
+#endif
+
+    ffi_call (&cif, method, &result, args);
     return result;
 }

----- End forwarded message -----

Re: [Linux-ia64] Fwd: Bug#129641: mozilla illegal instruction fault on IA64 (with a fix)

[Jim Wilson]

>This seems to be because in recent versions of g++ - since 3.0.2 according to
>the ChangeLog - class vtables are arrays of function descriptors (which are
>(code address, gp value) pairs) rather than arrays of function pointers (which
>are pointers to function descriptors).

This change was required by the C++ ABI.  If was always the intent to do
things this way, it just took a while to get around to it because there was
more compiler work than people available to do it.

Jim