Re: loading bundles stopped working

[David Chisnall]

On 28/11/2018 11:35, Sebastian Reitenbach wrote:
> (gdb) info break
> Num     Type           Disp Enb Address            What
> 1       breakpoint     keep y   0x0000093f1dcad9a2 in 
> initialize_gnustep_backend at NSApplication.m:309
>          breakpoint already hit 1 time
> 2       breakpoint     keep y   0x0000093ec291a170 in -[NSBundle load] at 
> NSBundle.m:1989
> 3       breakpoint     keep y   0x0000093ec2b2a750 in __objc_dynamic_link at 
> ././dynamic-load.h:63
> 5       breakpoint     keep y   0x0000093e64843ae0 in __objc_exec_class at 
> /home/ports/pobj/amd64/gnustep-libobjc2-1.9.0/libobjc2-1.9.0/loader.c:46
> (gdb) c
> Continuing.
>
> Breakpoint 2, -[NSBundle load] (self=0x93e9baac588, _cmd=0x93e69deea88) at 
> NSBundle.m:1989
> 1989    - (BOOL) load
> (gdb)
> Continuing.
>
> Breakpoint 3, __objc_dynamic_link (module=0x93f0c45f248 "8\212\273\302>\t", mode=2366, 
> debug_file=0x93f3d9fa8e0 <__sF+304> "") at ././dynamic-load.h:64
> warning: Source file is more recent than executable.
> 64      {
> (gdb)
> Continuing.
>
> Program received signal SIGFPE, Arithmetic exception.
> 0x0000093e70b4124c in _dl_find_symbol_obj (obj=0x93ecb3bbc00, 
> sl=0x7f7ffffd33f8) at /usr/src/libexec/ld.so/resolve.c:584
> 584             for (si = obj->buckets[sl->sl_elf_hash % obj->nbuckets];
>
> So I stopped at NSApplication.m:309, and then added the breakpoints in 
> dynamic-load.h and in libobjc loader.c where the __objc_exec_class resides, and 
> then continued to execute, but it doesn't hit the breakpoint 5 before throwing 
> the FPE.


Okay, it looks as if libraries that are linked with lld are not getting 
their global constructors called on OpenBSD.  Can you try this test?

=$ cat lib.c
#include <stdio.h>

__attribute__((constructor))
void load(void)
{
        puts("Library loaded");
}
[theraven@FBSDVM /tmp]$ cat loadlib.c
#include <dlfcn.h>
#include <stdio.h>

int main(void)
{
        puts("Program started");
        dlopen("./lib.so", RTLD_LAZY | RTLD_GLOBAL);
        return 0;
}
$ clang60 lib.c -shared -o lib.so -fPIC -fuse-ld=lld
$ clang loadlib.c
$ ./a.out
Program started
Library loaded


If it prints both of the lines above, the library was correctly loaded 
and the global constructors were run.  If it works with -fuse-ld=lld but 
not -fuse-ld=bfd, then that tells us that this really is the problem. 
Objdump of the bfd and lld versions of lib.so should help us identify 
the differences.

David