http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48109
Summary: Objective-C class defs/refs are lost under LTO on
Darwin for ABI0/1
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: objc
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ia...@gcc.gnu.org
Host: *-apple-darwin*
Target: *-apple-darwin*
Build: *-apple-darwin*
This is a FE bug that manifests only on Darwin/NeXT (m32) under LTO.
(originally reported as part of PR48094)
e.g.
-L/sw/src/fink.build/gcc46-4.6.0-1000/darwin_objdir/x86_64-apple-darwin10.7.0/i386/libobjc/.libs
-lobjc -m32 -o objc-dg-lto-trivial-1-21 (timeout = 300)
ld: warning: section __OBJC/__image_info has unexpectedly large size 16 in
/var/tmp//ccMlEsXS.lto.o^M
Undefined symbols for architecture i386:^M
".objc_class_name_myRootObject", referenced from:^M
pointer-to-literal-objc-class-name in ccMlEsXS.lto.o^M
pointer-to-literal-objc-class-name in ccMlEsXS.lto.o^M
ld: symbol(s) not found for architecture i386^M
---
The reason is an anachronism in using target macros to emit efficient
representations of class presence and requirement
(ASM_DECLARE_CLASS_REFERENCE/ASM_DECLARE_UNRESOLVED_REFERENCE).
.. because of this, there are no real vars representing the
presence/requirement for the classes and, when LTO is engaged, the information
is lost.
The separate external defs/refs are required because the class metadata
structures are all local to a given TU. The refs meet the linkage
requirements.
For the m64 ABI-2 this is not longer an issue, since class metadata definitions
are now external and thus visible without additional action.
