[Bug gdb/14100] internal-error: frame_cleanup_after_sniffer: Assertion `frame->prologue_cache == NULL' failed.

["tromey at redhat dot com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14100

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |tromey at redhat dot com

--- Comment #2 from Tom Tromey <tromey at redhat dot com> 2012-08-02 15:02:14 UTC ---
It was surprisingly hard to find out where the exception
is originally thrown.  I had to resort to some crazy hacks.

There are two possible problems.

One is that maybe this is just a bad assert.
Perhaps instead this cleanup should just clear the prologue_cache field.
This would make sense because it is hard to predict what code paths
might call QUIT.

Another is that dwarf2_frame_cache could assign to *this_cache
at the end of its processing, rather than at the beginning.

What is happening is that dwarf2_frame_cache sets *this_cache.
Then it does some more work; including eventually calling target_read,
which calls QUIT.  If the C-c arrives at exactly the right moment,
it triggers the failure.

#1  0x000000000074315e in target_read (ops=0x3b84890, 
    object=TARGET_OBJECT_STACK_MEMORY, annex=0x0, buf=0x3e89fc0 "", 
    offset=140737479962640, len=8) at ../../archer/gdb/target.c:2027
#2  0x0000000000742a9e in target_read_stack (memaddr=140737479962640, myaddr=
    0x3e89fc0 "", len=8) at ../../archer/gdb/target.c:1785
#3  0x000000000079e592 in read_stack (memaddr=140737479962640, myaddr=
    0x3e89fc0 "", len=8) at ../../archer/gdb/corefile.c:233
#4  0x00000000006bf20e in read_value_memory (val=0x3e42c00, 
    embedded_offset=0, stack=1, memaddr=140737479962640, buffer=0x3e89fc0 "", 
    length=8) at ../../archer/gdb/valops.c:1140
#5  0x00000000006bec15 in value_fetch_lazy (val=0x3e42c00)
    at ../../archer/gdb/valops.c:1022
#6  0x00000000006aed06 in value_entirely_available (value=0x3e42c00)
    at ../../archer/gdb/value.c:348
#7  0x0000000000818e29 in frame_register_unwind (frame=0x3bf7ec0, regnum=6, 
    optimizedp=0x7fffffb7517c, unavailablep=0x7fffffb75178, lvalp=
    0x7fffffb75168, addrp=0x7fffffb75170, realnump=0x7fffffb7516c, bufferp=
    0x7fffffb751c0 "ʠ\370\003\006") at ../../archer/gdb/frame.c:863
#8  0x00000000008190b3 in frame_unwind_register (frame=0x3bf7ec0, regnum=6, 
    buf=0x7fffffb751c0 "ʠ\370\003\006") at ../../archer/gdb/frame.c:912
#9  0x000000000081912d in get_frame_register (frame=0x3bf8d10, regnum=6, buf=
    0x7fffffb751c0 "ʠ\370\003\006") at ../../archer/gdb/frame.c:926
#10 0x00000000007ab399 in read_reg (baton=0x3bf8d10, reg=6)
    at ../../archer/gdb/dwarf2-frame.c:299
#11 0x00000000007ad205 in dwarf2_frame_cache (this_frame=0x3bf8d10, 
    this_cache=0x3bf8d28) at ../../archer/gdb/dwarf2-frame.c:1090

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