gcj on OpenBSD

Wed Mar 11 16:53:00 GMT 2009

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:
0000000000400bb0 <_init>:
 400bb0: 48 83 ec 08 sub 0ドルx8,%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 0ドルx8,%rsp
 400bc7: c3 retq
which calls (*_Jv_RegisterClasses)
0000000000400db0 <frame_dummy>:
 400db0: 55 push %rbp
 400db1: 48 83 3d 87 04 20 00 cmpq 0ドルx0,0x200487(%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 0ドルx400c18 <_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 0ドルx601240 <__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.