[plt-scheme] in need for a hint to debug a crash

I am  using PLT 372 on a  i686-pc-linux-gnu, Slackware Linux
12.0.0, GCC 4.1.2, built and installed from source with:

| configure \
|   --enable-shared --enable-cgcdefault \
|   CFLAGS="-O3 -march=i686 -mtune=i686 \
|           -I/opt/gnome-2.20/include -L/opt/gnome-2.20/lib"

and I get the same behaviour with PLT 371 (I was not able to
install PLT 3.99).  I am  coding a module implemented by a C
shared library built with:

| configure CFLAGS="-O3 -g -march=i686 -mtune=i686"

In it I  define my own MzScheme primitive  types as wrappers
of "Scheme_Object".  One of the types I am allocating, has a
block of memory of less than  128 bytes and I get crashes in
the process when allocating with:

| scheme_malloc_fail_ok(scheme_malloc, block_size);

the crash always happens when  I run my test suite, but when
I change something in the code the point of crash changes.

The  crash happens  in the  MzScheme code,  and it  seems to
reliably go away  if I arbitrarily change the  block size to
more than 1024 bytes; that is I get the crash with:

| scheme_malloc_fail_ok(scheme_malloc, 1024);

but I do not get it with:

| scheme_malloc_fail_ok(scheme_malloc, 1025);

What  the hell?   When I  alloc  1025 bytes  the test  suite
completes with no errors, and to the best of my knowledge so
far that means that the structures are not corrupted because
the purpose of the suite  is exactly to test manipulation of
their  fields,   including  validation  of   SCHEME_TYPE  of
"Scheme_Object".

Program received signal SIGSEGV, Segmentation fault.
do_clear_symbols (t=0x8aefe10, start=0, offset=8,
addr=145686528, clearing=0) at ./codetab.inc:227
227	      if (!*(Scheme_Type *)val) {
#0  do_clear_symbols (t=0x8aefe10, start=0, offset=8,
addr=145686528, clearing=0) at ./codetab.inc:227
#1  0x400892f9 in do_clear_symbols (t=0x8aefe60, start=0,
offset=12, addr=145686528, clearing=0) at ./codetab.inc:229
#2  0x400892f9 in do_clear_symbols (t=0x8aadf50, start=0,
offset=16, addr=144703488, clearing=0) at ./codetab.inc:229
#3  0x400892f9 in do_clear_symbols (t=0x811b2d0, start=0,
offset=20, addr=134217728, clearing=0) at ./codetab.inc:229
#4  0x400892f9 in do_clear_symbols (t=0x811b320, start=0,
offset=24, addr=0, clearing=0) at ./codetab.inc:229
#5  0x400892f9 in do_clear_symbols (t=0x811b370, start=0,
offset=28, addr=0, clearing=0) at ./codetab.inc:229
#6  0x40089425 in scheme_clean_native_symtab () at
./codetab.inc:262
#7  0x4012c948 in clean_symbol_table () at ./symbol.c:242
#8  0x401ce4f6 in GC_finalize () at ./finalize.c:882
#9  0x401c4420 in GC_finish_collection () at ./alloc.c:681
#10 0x401c4f85 in GC_try_to_collect_inner
(stop_func=0x401c3f50 <GC_never_stop_func>) at ./alloc.c:395
#11 0x401c552b in GC_collect_or_expand (needed_blocks=1,
ignore_off_page=0) at ./alloc.c:1051
#12 0x401c569c in GC_allocobj (sz=4, kind=1) at ./alloc.c:1106
#13 0x401d0de7 in GC_generic_malloc_inner (lb=12, k=1) at
./malloc.c:138
#14 0x401d0ea5 in GC_generic_malloc (lb=12, k=1) at
./malloc.c:194
#15 0x401d1056 in GC_malloc (lb=12) at ./malloc.c:319
#16 0x40098b3e in scheme_make_pair (car=0x8b38b70,
cdr=0x8b3fbb0) at ./list.c:561
#17 0x401244d3 in scheme_add_rename (o=0x8b3e000,
rename=0x8b38b70) at ./stxobj.c:1375
#18 0x40124909 in propagate_wraps (o=0x8b3e000, len=4,
_ml=0xbfc6ffec, owner_wraps=0x8b41170) at ./stxobj.c:1801
#19 0x40124a8f in scheme_stx_content (o=0x8b43fe0) at
./stxobj.c:2182
#20 0x400533a0 in scheme_compile_expand_expr (form=<value
optimized out>, env=<value optimized out>, rec=0xbfc70108, 
    drec=0, app_position=0) at ./eval.c:4247
#21 0x40053be8 in scheme_expand_list (form=0x8b42160,
env=0x8a7b5b0, erec=0xbfc70398, drec=0) at ./eval.c:5390
#22 0x40057830 in compile_expand_app (forms=0x8b43ee0,
env=0x8a7b5b0, rec=0xbfc70398, drec=0) at ./eval.c:4685
#23 0x400537fa in scheme_compile_expand_expr (form=<value
optimized out>, env=<value optimized out>, rec=0xbfc70398, 
    drec=0, app_position=0) at ./eval.c:4426
#24 0x401321f3 in do_let_expand (form=0x8b42380,
origenv=0x8a7b620, erec=0xbfc704f8, drec=0, 
    formname=0x40156699 "letrec-values", letrec=1, multi=1,
letstar=0, env_already=0x0) at ./syntax.c:4086
#25 0x401327ba in letrec_values_expand (form=0x8b42380,
env=0x8a7b620, erec=0xbfc704f8, drec=0) at ./syntax.c:4141
#26 0x400538ae in scheme_compile_expand_expr (form=<value
optimized out>, env=<value optimized out>, rec=0xbfc704f8, 
    drec=0, app_position=0) at ./eval.c:4308
#27 0x40053be8 in scheme_expand_list (form=0x8b41360,
env=0x8a7b620, erec=0xbfc706f8, drec=0) at ./eval.c:5390
#28 0x40055d65 in scheme_compile_expand_block (forms=<value
optimized out>, env=0x8a7b620, rec=0xbfc706f8, drec=0)
    at ./eval.c:5271
#29 0x4013250a in do_let_expand (form=0x8b3e4a0,
origenv=0x8a7b9a0, erec=0xbfc70858, drec=0, 
    formname=0x401566a7 "let-values", letrec=0, multi=1,
letstar=0, env_already=0x0) at ./syntax.c:4114

-- 
Marco Maggi

"Now feel the funk blast!"
Rage Against the Machine - "Calm like a bomb"