gcj on OpenBSD

[Andrew Haley]

Andrew Haley wrote:
> Kurt Miller wrote:
> 
>> I've been working on getting gcj up and running on OpenBSD/i386.
>> Currently I'm working on adding gcj to gcc 4.2 port. I'm pretty far
>> along with the work: enabled dwarf2 exceptions, thread model posix, etc.
>> The build completes but gcj-dbtool segfaults and gij too. The segfault
>> occurs when initializing the class loader because engine is null.
>>
>> Could anyone suggest some ideas for diagnosing the root cause of this?
> 
> This happens because class registration hasn't been done.  gcc generates
> a magic section called .jcr, and this is a list of pointers to classes.
> 
> On x86_64 a .jcr section in an .o file with two classes looks like this:
> 
> RELOCATION RECORDS FOR [.jcr]:
> OFFSET           TYPE              VALUE
> 0000000000000000 R_X86_64_64       P::class$
> 0000000000000008 R_X86_64_64       Hello::class$
> 
> And the .init section:

Of an executable, I mean.  There is no init section in the .o file.

> 0000000000400bb0 <_init>:
>   400bb0:       48 83 ec 08             sub    $0x8,%rsp
>   400bb4:       e8 63 01 00 00          callq  400d1c <call_gmon_start>
>   400bb9:       e8 f2 01 00 00          callq  400db0 <frame_dummy>
>   400bbe:       e8 2d 04 00 00          callq  400ff0 <__do_global_ctors_aux>
>   400bc3:       48 83 c4 08             add    $0x8,%rsp
>   400bc7:       c3                      retq
> 
> which calls (*_Jv_RegisterClasses)
> 
> 0000000000400db0 <frame_dummy>:
>   400db0:       55                      push   %rbp
>   400db1:       48 83 3d 87 04 20 00    cmpq   $0x0,0x200487(%rip)        # 601240 <__JCR_LIST__>
>   400db8:       00
>   400db9:       48 89 e5                mov    %rsp,%rbp
>   400dbc:       74 1a                   je     400dd8 <frame_dummy+0x28>
>   400dbe:       41 bb 18 0c 40 00       mov    $0x400c18 <_Jv_RegisterClasses@plt>,%r11d
>   400dc4:       4d 85 db                test   %r11,%r11
>   400dc7:       74 0f                   je     400dd8 <frame_dummy+0x28>
>   400dc9:       bf 40 12 60 00          mov    $0x601240 <__JCR_LIST__>,%edi
>   400dce:       c9                      leaveq
>   400dcf:       41 ff e3                jmpq   *%r11
>   400dd2:       66 0f 1f 44 00 00       nopw   0x0(%rax,%rax,1)
>   400dd8:       c9                      leaveq
>   400dd9:       c3                      retq
> 
> I suspect that this mechanism is not working on BSD.
> 
> Andrew.