This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: info frame ADDR internal error
On Sunday 25 January 2009 19:44:32, Pedro Alves wrote:
> :-(
>
> Was going to commit the patch, but then I tried it on x86 (I was on x86-64 before) ...
I actually went ahead, and committed the patch. It fixes some bogosity,
and uncovers the next problem. This should help everyone else who
wants to look at the issue.
>
> (top-gdb) bt
> #0 main (argc=1, argv=0xffffd524) at ../../src/gdb/gdb.c:28
>
> (top-gdb) info frame 1
> Stack frame at 0x1:
> eip = 0x0; saved eip 0xf7f26f59
>
> Breakpoint 1, internal_error (file=0x8314a4f "../../src/gdb/valops.c", line=662,
> string=0x8314a19 "%s: Assertion `%s' failed.") at ../../src/gdb/utils.c:972
> 972 va_start (ap, string);
>
> (top-gdb) bt
> #0 internal_error (file=0x8314a4f "../../src/gdb/valops.c", line=662, string=0x8314a19 "%s: Assertion `%s' failed.")
> at ../../src/gdb/utils.c:972
> #1 0x08116c44 in value_fetch_lazy (val=0x883f960) at ../../src/gdb/valops.c:662
> #2 0x0810b766 in value_contents_all (value=0x883f960) at ../../src/gdb/value.c:375
> #3 0x081efd43 in frame_register_unwind (frame=0x8421250, regnum=5, optimizedp=0xffc759f4, lvalp=0xffc759e8,
> addrp=0xffc759f0, realnump=0xffc759ec, bufferp=0xffc75a40 "...") at ../../src/gdb/frame.c:603
> #4 0x081eff19 in frame_unwind_register (frame=0x8421250, regnum=5, buf="...") at ../../src/gdb/frame.c:639
> #5 0x081eff3d in get_frame_register (frame=0x84212e4, regnum=5, buf="...") at ../../src/gdb/frame.c:647
> #6 0x0809c2b7 in i386_frame_cache (this_frame=0x84212e4, this_cache=0x84212e8) at ../../src/gdb/i386-tdep.c:1306
> #7 0x0809c47e in i386_frame_this_id (this_frame=0x84212e4, this_cache=0x84212e8, this_id=0x8421304)
> at ../../src/gdb/i386-tdep.c:1369
> #8 0x081ef2cb in get_frame_id (fi=0x84212e4) at ../../src/gdb/frame.c:261
> #9 0x081f194d in get_frame_base (fi=0x84212e4) at ../../src/gdb/frame.c:1666
> #10 0x0814cd44 in frame_info (addr_exp=0x83f5133 "1", from_tty=1) at ../../src/gdb/stack.c:995
> #11 0x080d51b7 in do_cfunc (c=0x84187c0, args=0x83f5133 "1", from_tty=1) at ../../src/gdb/cli/cli-decode.c:67
>
> Here's the offender:
>
> int
> value_fetch_lazy (struct value *val)
> {
> gdb_assert (value_lazy (val));
> allocate_value_contents (val);
> if (VALUE_LVAL (val) == lval_memory)
> {
> CORE_ADDR addr = VALUE_ADDRESS (val) + value_offset (val);
> int length = TYPE_LENGTH (check_typedef (value_enclosing_type (val)));
>
> if (length)
> read_memory (addr, value_contents_all_raw (val), length);
> }
> else if (VALUE_LVAL (val) == lval_register)
> {
> struct frame_info *frame;
> int regnum;
> struct type *type = check_typedef (value_type (val));
> struct value *new_val = val, *mark = value_mark ();
>
> /* Offsets are not supported here; lazy register values must
> refer to the entire register. */
> gdb_assert (value_offset (val) == 0);
>
> while (VALUE_LVAL (new_val) == lval_register && value_lazy (new_val))
> {
> frame = frame_find_by_id (VALUE_FRAME_ID (new_val));
> ^^^^^^^^^^^^^^^^
> regnum = VALUE_REGNUM (new_val);
>
> gdb_assert (frame != NULL);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> (top-gdb) p VALUE_FRAME_ID (new_val)
> $1 = {stack_addr = 1, code_addr = 0, special_addr = 0, stack_addr_p = 1, code_addr_p = 1, special_addr_p = 0}
>
> The new frame that create_new_frame created, isn't linked in the
> regular ( current_frame->... ) frame chain, it lives in its own chain,
> so this frame_find_by_id call isn't going to find it, unless you
> get lucky.
>
> This reinforces the bad things I was saying about create_new_frame.
>
> Any suggestions on how this could be fixed?
>
> Before we go farther, is this a valid use case at all? Could
> we rip this piece of parse_frame_specification_1 out instead? It's been
> broken for years now --- I can reproduce the original internal error
> on gdb-6.0:
>
> >./gdb ./gdb
> GNU gdb 6.0
> Copyright 2003 Free Software Foundation, Inc.
> ...
> (top-gdb) b main
> Breakpoint 3 at 0x8077aa4: file ../../gdb-6.0/gdb/gdb.c, line 30.
> (top-gdb) r
> Starting program: /home/pedro/gdb/ancient/build-6.0/gdb/gdb
> Breakpoint 3, main (argc=1, argv=0xffd15254) at ../../gdb-6.0/gdb/gdb.c:30
> 30 memset (&args, 0, sizeof args);
> (top-gdb) info frame 1
> Stack frame at 0x1:
> eip = 0x0; saved eip
> ../../gdb-6.0/gdb/dwarf2-frame.c:518: internal-error: dwarf2_frame_cache: Assertion `fde != NULL' failed.
>
> Note that "info frame ADDR" and "frame ADDR" do look for a frame in
> the regular chain that matches ADDR, before resorting to hacking up
> a new one with create_new_frame.
>
--
Pedro Alves