Re: strings referred to by Vsjis_coding_system, Vbig5_coding_system

[Dan Nicolaescu <dann@ics.uci.edu>]

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Kenichi Handa <handa@m17n.org> writes:

  > In article <200911112142.nABLgZwS024554@godzilla.ics.uci.edu>, Dan Nicolaescu <dann@ics.uci.edu> writes:
  > 
  > > Handa-san,
  > > Strings like this:
  > 
  > > ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ
  > 
  > > are found in the GC memory in emacs, they are referred to by
  > > Vsjis_coding_system, Vbig5_coding_system, and maybe other variables.
  > 
  > > Is there any chance that such strings can be put in pure memory?
  > > Not sure where they are created, and what they do...
  > 
  > I have no idea.  Are you sure that those variables refer
  > that string?  According to the following gdb session, at
  > least Vbig5_coding_system doesn't refer such a string
  > directly.
  > 

I can't find one at the moment, and unfortunately I did not save a
debugging session.
All the ones that I find at the moment are referred to from Vcoding_system_hash_table.
Can you please figure out this one?

[Note that I have some instrumentation code in alloc.c, so the line
number will not match, but none of the semantics are changed]


Breakpoint 3, mark_object (arg=0x84d8e99) at alloc.c:5538
5538		MARK_STRING (ptr);
Missing separate debuginfos, use: debuginfo-install alsa-lib-1.0.21-3.fc11.i586 atk-1.25.2-2.fc11.i586 bzip2-libs-1.0.5-5.fc11.i586 cairo-1.8.8-1.fc11.i586 dbus-libs-1.2.12-2.fc11.i586 e2fsprogs-libs-1.41.4-12.fc11.i586 expat-2.0.1-6.fc11.1.i586 fontconfig-2.7.1-1.fc11.i586 freetype-2.3.9-5.fc11.i586 giflib-4.1.6-2.fc11.i586 glib2-2.20.5-1.fc11.i586 glibc-2.10.1-5.i686 gpm-libs-1.20.6-3.fc11.i586 gtk-nodoka-engine-0.7.2-5.fc11.i586 gtk2-2.16.6-2.fc11.i586 libICE-1.0.4-7.fc11.i586 libSM-1.1.0-4.fc11.i586 libX11-1.2.2-1.fc11.i586 libXau-1.0.4-5.fc11.i586 libXcomposite-0.4.0-7.fc11.i586 libXcursor-1.1.9-4.fc11.i586 libXdamage-1.1.1-6.fc11.i586 libXext-1.0.99.1-3.fc11.i586 libXfixes-4.0.3-5.fc11.i586 libXft-2.1.13-2.fc11.i586 libXi-1.2.1-1.fc11.i586 libXinerama-1.0.3-4.fc11.i586 libXpm-3.5.7-5.fc11.i586 libXrandr-1.2.99.4-3.fc11.i586 libXrender-0.9.4-5.fc11.i586 libattr-2.4.43-3.fc11.i586 libcap-2.16-4.fc11.1.i586 libcroco-0.6.2-2.fc11.i586 libgsf-1.14.11-3.fc11.i586 libjpeg-6b-45.fc11.i586 libpng-1.2.37-1.fc11.i586 librsvg2-2.26.0-1.fc11.i586 libselinux-2.0.80-1.fc11.i586 libtiff-3.8.2-14.fc11.i586 libxcb-1.2-4.fc11.i586 libxml2-2.7.6-1.fc11.i586 ncurses-libs-5.7-2.20090207.fc11.i586 pango-1.24.5-1.fc11.i586 pixman-0.14.0-2.fc11.i586 zlib-1.2.3-22.fc11.i586
(gdb) pp arg
"ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ\0"
(gdb) up
#1  0x0817c5af in mark_vectorlike (ptr=0x862bf10) at alloc.c:5419
5419	    mark_object (ptr->contents[i]);
(gdb) up
#2  0x0817c974 in mark_object (arg=0x862bf15) at alloc.c:5640
5640		mark_vectorlike (XVECTOR (obj));
(gdb) pp arg
[]
(gdb) up
#3  0x0817c5af in mark_vectorlike (ptr=0x8552298) at alloc.c:5419
5419	    mark_object (ptr->contents[i]);
(gdb) pp arg
#4  0x0817c974 in mark_object (arg=0x855229d) at alloc.c:5640
5640		mark_vectorlike (XVECTOR (obj));
(gdb) pp arg
[]
(gdb) up
#5  0x0817c5af in mark_vectorlike (ptr=0x864ab48) at alloc.c:5419
5419	    mark_object (ptr->contents[i]);
(gdb) pp arg
No symbol "arg" in current context.
(gdb) up
#6  0x0817c974 in mark_object (arg=0x864ab4d) at alloc.c:5640
5640		mark_vectorlike (XVECTOR (obj));
(gdb) pp arg
[]
(gdb) up
#7  0x0817c910 in mark_object (arg=0x8429f2d) at alloc.c:5629
5629			MAYBE_MARK_OBJECT (h->key_and_value);
(gdb) pp arg
#s(hash-table size -2147482553 test eq rehash-size 1.5 rehash-threshold 0.8 data ())
(gdb) up
#8  0x0817be26 in Fgarbage_collect () at alloc.c:5108
5108	    mark_object (*staticvec[i]);
(gdb) p i
$1 = 0x1a4

0x1a4 in staticvec corresponds to Vcoding_system_hash_table.

  > By the way, I've just found that "pr" command doesn't work
  > with the latest code:
  > 
  > (gdb) p Vbig5_coding_system
  > $1 = 139728474
  > (gdb) pr
  > Cannot access memory at address 0x842e030

I've found many instances where "pr" crashes the debugger...