[Bug tui/14880] In split register layouts, `up` results in assertion failure in value.c

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14880

--- Comment #5 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
CVSROOT:    /cvs/src
Module name:    src
Branch:     gdb_7_6-branch
Changes by:    palves@sourceware.org    2013-06-28 12:39:00

Modified files:
    gdb            : ChangeLog value.c value.h 
    gdb/tui        : tui-regs.c 

Log message:
    [PR tui/14880] Fetch values before comparing their contents.

    PR tui/14880 shows a reproducer that triggers this assertion:

    int
    value_available_contents_eq (const struct value *val1, int offset1,
    const struct value *val2, int offset2,
    int length)
    {
    int idx1 = 0, idx2 = 0;

    /* This routine is used by printing routines, where we should
    already have read the value.  Note that we only know whether a
    value chunk is available if we've tried to read it.  */
    gdb_assert (!val1->lazy && !val2->lazy);

    (top-gdb) bt
    #0  internal_error (file=0x88a26c "../../src/gdb/value.c", line=549,
string=0x88a220 "%s: Assertion `%s' failed.") at ../../src/gdb/utils.c:844
    #1  0x000000000057b9cd in value_available_contents_eq (val1=0x10fa900,
offset1=0, val2=0x10f9e10, offset2=0, length=8) at ../../src/gdb/value.c:549
    #2  0x00000000004fd756 in tui_get_register (frame=0xd5c430, data=0x109a548,
regnum=0, changedp=0x109a560) at ../../src/gdb/tui/tui-regs.c:736
    #3  0x00000000004fd111 in tui_check_register_values (frame=0xd5c430) at
../../src/gdb/tui/tui-regs.c:521
    #4  0x0000000000501884 in tui_check_data_values (frame=0xd5c430) at
../../src/gdb/tui/tui-windata.c:234
    #5  0x00000000004f976f in tui_selected_frame_level_changed_hook (level=1)
at ../../src/gdb/tui/tui-hooks.c:222
    #6  0x00000000006f0681 in select_frame (fi=0xd5c430) at
../../src/gdb/frame.c:1490
    #7  0x00000000005dd94b in up_silently_base (count_exp=0x0) at
../../src/gdb/stack.c:2268
    #8  0x00000000005dd985 in up_command (count_exp=0x0, from_tty=1) at
../../src/gdb/stack.c:2280
    #9  0x00000000004dc5cf in do_cfunc (c=0xd3f720, args=0x0, from_tty=1) at
../../src/gdb/cli/cli-decode.c:113
    #10 0x00000000004df664 in cmd_func (cmd=0xd3f720, args=0x0, from_tty=1) at
../../src/gdb/cli/cli-decode.c:1888
    #11 0x00000000006e43e1 in execute_command (p=0xc7e6c2 "", from_tty=1) at
../../src/gdb/top.c:489

    The fix is to fetch the value before comparing the contents.  The
    comment additions to value.h explain why it can't be
    value_available_contents_eq itself that fetches the contents.

    Tested on x86_64 Fedora 17.

    gdb/
    2013-06-28  Pedro Alves  <palves@redhat.com>

    PR tui/14880
    * tui/tui-regs.c (tui_get_register): Fetch register value contents
    before checking whether they're available.
    * value.c (value_available_contents_eq): Change comment.
    * value.h (value_available_contents_eq): Expand comment.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/ChangeLog.diff?cvsroot=src&only_with_tag=gdb_7_6-branch&r1=1.15260.2.56&r2=1.15260.2.57
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/value.c.diff?cvsroot=src&only_with_tag=gdb_7_6-branch&r1=1.167&r2=1.167.2.1
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/value.h.diff?cvsroot=src&only_with_tag=gdb_7_6-branch&r1=1.218&r2=1.218.2.1
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/tui/tui-regs.c.diff?cvsroot=src&only_with_tag=gdb_7_6-branch&r1=1.48&r2=1.48.2.1

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