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Re: GMC release

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From:
Andy Dougherty
Date:
September 1, 2005 08:21
Subject:
Re: GMC release
Message ID:
Pine.SOC.4.62.0509011114110.21598@maxwell.phys.lafayette.edu
On Thu, 1 Sep 2005, Nattfodd wrote:

> today is the deadline for the google summer of code projects, and it's time
> anyway for a "release" of GMC.
> GMC is a generational garbage collector for parrot that allows copying of
> objects and thus copying GC schemes.

Thanks for submitting this.  I also appreciated the extensive comments in 
the source (even if I didn't actually read most of them :-).

> svn co https://svn.perl.org/parrot/branches/gmc

First, I needed the following simple patch to MANIFEST

--- gmc/MANIFEST	Thu Sep  1 09:12:48 2005
+++ parrot-andy/MANIFEST	Thu Sep  1 10:19:20 2005
@@ -1639,6 +1639,7 @@
 src/exec_start.c                                  []
 src/exit.c                                        []
 src/extend.c                                      []
+src/gc_gmc.c                                      []
 src/gc_gms.c                                      []
 src/gc_ims.c                                      []
 src/generic_register.c                            []


After that, with Sparc/Solaris 8, with Sun's CC, I got a core dump
even on a simple

	./miniparrot -h

I rebuilt with debugging, and it again core dumped (although somewhere 
else).  Here's the backtrace: 

(dbx) run -h
Running: miniparrot -h 
(process id 21433)
t@1 (l@1) signal SEGV (no mapping at the fault address) in gc_gmc_copy_gen at line 879 in file "gc_gmc.c"
  879           PMC_body(Gmc_PMC_hdr_get_PMC(ptr)) = Gmc_PMC_hdr_get_BODY(ptr);
(dbx) where
current thread: t@1
=>[1] gc_gmc_copy_gen(from = 0x32dbe8, dest = 0x4d31f8), line 879 in "gc_gmc.c"
  [2] gc_gmc_more_bodies(interpreter = 0x2b6ce8, pool = 0x31d860), line 933 in "gc_gmc.c"
  [3] gc_gmc_new_body(interpreter = 0x2b6ce8, pool = 0x31d860, size = 40U, aggreg = 4), line 705 in "gc_gmc.c"
  [4] gc_gmc_get_free_object_of_size(interpreter = 0x2b6ce8, pool = 0x31d860, size = 40U, aggreg = 4), line 741 in "gc_gmc.c"
  [5] gc_gmc_get_free_typed_object(interpreter = 0x2b6ce8, pool = 0x31d860, base_type = 62), line 796 in "gc_gmc.c"
  [6] new_pmc_alloc_header(interpreter = 0x2b6ce8, flags = 132096U, is_typed = 1, base_type = 62), line 270 in "headers.c"
  [7] new_pmc_typed_header(interpreter = 0x2b6ce8, flags = 132096U, base_type = 62), line 343 in "headers.c"
  [8] get_new_pmc_header(interpreter = 0x2b6ce8, base_type = 62, flags = 132096U), line 231 in "pmc.c"
  [9] constant_pmc_new(interpreter = 0x2b6ce8, base_type = 62), line 310 in "pmc.c"
  [10] mmd_create_builtin_multi_meth_2(interpreter = 0x2b6ce8, func_nr = 5, type = 33, right = -100, func_ptr = 0x1edce0 = &Parrot_Complex_i_multiply_int()), line 2116 in "mmd.c"
  [11] mmd_create_builtin_multi_meth(interpreter = 0x2b6ce8, type = 33, entry = 0xffbef444), line 2139 in "mmd.c"
  [12] Parrot_mmd_register_table(interpreter = 0x2b6ce8, type = 33, mmd_table = 0xffbef2e4, n = 35), line 2182 in "mmd.c"
  [13] Parrot_Complex_class_init(interp = 0x2b6ce8, entry = 33, pass = 1), line 1390 in "complex.c"
  [14] Parrot_initialize_core_pmcs(interp = 0x2b6ce8), line 126 in "core_pmcs.c"
  [15] init_world(interpreter = 0x2b6ce8), line 85 in "global_setup.c"
  [16] Parrot_init(interpreter = 0x2b6ce8), line 84 in "embed.c"
  [17] make_interpreter(parent = (nil), flags = PARROT_NO_FLAGS), line 165 in "inter_create.c"
  [18] Parrot_new(parent = (nil)), line 47 in "embed.c"
  [19] main(argc = 2, argv = 0xffbefa8c), line 452 in "main.c"

I #defined GMC_DEBUG and BIG_DUMP, and the last entries may be relevant:

Copying gen (32e730,32f760) to gen (4d3d40,4d4d70)
copy_gen: ptr 4c0904, old_body 32f554, new_body 4d4b64, struct_val: deadbeef
copy_gen: ptr 47e078, old_body 32f57c, new_body 4d4b8c, struct_val: deadbeef
copy_gen: ptr 46f7bc, old_body 32f5a4, new_body 4d4bb4, struct_val: deadbeef
copy_gen: ptr 4683d8, old_body 32f5cc, new_body 4d4bdc, struct_val: deadbeef
copy_gen: ptr 46845c, old_body 32f5f4, new_body 4d4c04, struct_val: deadbeef
copy_gen: ptr 4684d4, old_body 32f61c, new_body 4d4c2c, struct_val: deadbeef
copy_gen: ptr 3555a4, old_body 32f644, new_body 4d4c54, struct_val: deadbeef
copy_gen: ptr 3555b0, old_body 32f66c, new_body 4d4c7c, struct_val: deadbeef
copy_gen: ptr 355820, old_body 32f694, new_body 4d4ca4, struct_val: deadbeef

Overall, I wonder if it's an alignment issue, since SPARC tends to be
much more sensitve to that than x86.  I haven't looked deeply at the
code at all, but do you do anything special to ensure that the blocks
of memory you are moving around maintain their aligment?

-- 
    Andy Dougherty		doughera@lafayette.edu

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