Re: libobjc2 relocation issue in aarch64

[Jordan Schidlowsky]

So after moving a few things to shared libraries, I started experiencing some 
strange things with the new runtime...  I'm running under asan and compiling 
and running latest libobjc2 master branch for arm-v7a android.  Compiler is 
Frederik's latest here: https://github.com/gnustep/tools-android 

So I'm ending up hitting an assert in the runtime on the second __objc_load 
when loading libs-base shared lib.  (first __objc_load on libobjc2 completes 
fine).

When __objc_load is called the second time when loading libs-base, I end up 
hitting this assert below (loader.c line 225):

assert((((uintptr_t)init->cat_end-(uintptr_t)init->cat_begin) % 
sizeof(*init->cat_begin)) == 0);

The category end minus start size ends up being 8992, and the size of the cat 
struct is 28.   

Any thoughts?
-Jordan


> On Jul 17, 2019, at 2:42 PM, Jordan Schidlowsky <address@hidden> wrote:
> 
> Yep.  Shared library removes the relocation problem.   There's no real reason 
> why I'm static linking libobjc in, I'm fine to move to a shared lib.  Thanks!
> 
> 
>> On Jul 17, 2019, at 1:56 PM, David Chisnall <address@hidden> wrote:
>> 
>> I think the main hint is to use a dynamic library.  Static linking is not 
>> well tested on any platform and the assembly code expects a PIC model.  I’m 
>> happy to accept patches that improve the static linking experience, but it’s 
>> not something that I have any plans to work on personally.
>> 
>> David
>> 
>>> On 17 Jul 2019, at 20:43, Jordan Schidlowsky <address@hidden> wrote:
>>> 
>>> I can't seem to get libobjc2 to link in properly to my android app on 
>>> arm64-v8a.  I'm using the latest clang prebuilt by Frederik here: 
>>> https://github.com/gnustep/tools-android    
>>> 
>>> I've tried 3 different linkers, and all report the same 
>>> R_AARCH64_ADR_PREL_LO21 issue.  bfd was the only linker to provide any 
>>> insight, but it seems like it's related to the SmallObjectClasses symbol.   
>>> Output from each linker is below:
>>> 
>>> gold:
>>> libs/libobjc2/objc_msgSend.aarch64.S:97: error: relocation overflow in 
>>> R_AARCH64_ADR_PREL_LO21
>>> 
>>> lld:
>>> ld.lld: error: 
>>> ../../../../libs/libobjc2/objc_msgSend.aarch64.S:97:(.text+0xD0): 
>>> relocation R_AARCH64_ADR_PREL_LO21 out of range: 16077624 is not in 
>>> [-1048576, 1048575]
>>> 
>>> bfd:
>>> libs/libobjc2/libobjc.a(objc_msgSend.S.o): In function 
>>> `objc_msgSend_stret': libs/libobjc2/objc_msgSend.aarch64.S:97:(.text+0xd0): 
>>> relocation truncated to fit: R_AARCH64_ADR_PREL_LO21 against symbol 
>>> `SmallObjectClasses' defined in COMMON section in 
>>> libs/libobjc2/libobjc.a(class_table.c.o)
>>> 
>>> 
>>> Any thoughts?
>>> -Jordan
>> 
>