Re: gdb/1799: $fp is not a left value, would be useful to be

[Samuel Thibault <samuel dot thibault at ens-lyon dot org>]

The following reply was made to PR gdb/1799; it has been noted by GNATS.

From: Samuel Thibault <samuel.thibault@ens-lyon.org>
To: Daniel Jacobowitz <drow@false.org>
Cc: gdb-gnats@sources.redhat.com
Subject: Re: gdb/1799: $fp is not a left value, would be useful to be
Date: Mon, 29 Nov 2004 21:48:50 +0100

 Hi,
 
 Le dim 28 nov 2004 à 18:34:53 -0500, Daniel Jacobowitz a tapoté sur son clavier :
 > On Sun, Nov 28, 2004 at 01:55:50AM +0100, Samuel Thibault wrote:
 > >     set $eip=$marcel_saved_pc
 > >     set $esp=$marcel_saved_sp
 > >     set $ebp=$marcel_saved_bp
 > 
 > > (gdb) rest-ctx
 > > Cannot access memory at address 0x40000000
 > 
 > I imagine GDB is trying to reset the notion of the frame in here somewhere.
 > then because the registers are in an inconsistent state something goes
 > wrong.  You may want to debug GDB, putting a breakpoint on
 > memory_error, to see where the access came from.
 
 Here it is:
 
 #0  memory_error (status=5, memaddr=0x40000000) at corefile.c:211
 #1  0x08084608 in read_memory (memaddr=0x40000000, myaddr=0xbfffc220 "", len=4)
     at corefile.c:239
 #2  0x08090060 in i386_frame_prev_register (next_frame=0x88ed944, 
     this_cache=0x88ed9e4, regnum=8, optimizedp=0xbfffc204, lvalp=0xbfffc1f8, 
     addrp=0xbfffc200, realnump=0xbfffc1fc, valuep=0xbfffc220)
     at i386-tdep.c:1015
 #3  0x0808bde6 in frame_register_unwind (frame=0x88ed9e0, regnum=8, 
     optimizedp=0xbfffc204, lvalp=0xbfffc1f8, addrp=0xbfffc200, 
     realnump=0xbfffc1fc, bufferp=0xbfffc220) at frame.c:542
 #4  0x0808c0b0 in frame_unwind_register (frame=0x88ed9e0, regnum=8, 
     buf=0xbfffc220) at frame.c:594
 #5  0x0808fcaf in i386_unwind_pc (gdbarch=0x8338680, next_frame=0x88ed9e0)
     at i386-tdep.c:854
 #6  0x0812fcf5 in gdbarch_unwind_pc (gdbarch=0x8338680, next_frame=0x88ed9e0)
     at gdbarch.c:3086
 #7  0x0808ba53 in frame_pc_unwind (this_frame=0x88ed9e0) at frame.c:411
 #8  0x080903ba in i386_unwind_dummy_id (gdbarch=0x8338680, 
     next_frame=0x88ed9e0) at i386-tdep.c:1165
 #9  0x0812dd51 in gdbarch_unwind_dummy_id (gdbarch=0x8338680, info=0x88ed9e0)
     at gdbarch.c:2316
 #10 0x080ebb61 in dummy_frame_sniffer (self=0x8282dc8, next_frame=0x88ed9e0, 
     this_prologue_cache=0x88eda80) at dummy-frame.c:144
 #11 0x0808d8e7 in frame_unwind_find_by_frame (next_frame=0x88ed9e0, 
     this_cache=0x88eda80) at frame-unwind.c:104
 #12 0x0808b43c in get_frame_id (fi=0x88eda7c) at frame.c:221
 #13 0x0808b968 in frame_find_by_id (id=
       {stack_addr = 3221158368, code_addr = 134594295, special_addr = 0, stack_addr_p = 1, code_addr_p = 1, special_addr_p = 0}) at frame.c:372
 #14 0x080f6d1e in value_assign (toval=0x8801d10, fromval=0x88c4598)
     at valops.c:721
 #15 0x080f371a in evaluate_subexp_standard (expect_type=0x0, exp=0x88c46d8, 
     pos=0xbfffcdc4, noside=EVAL_NORMAL) at eval.c:1455
 #16 0x080eff42 in evaluate_subexp (expect_type=0x0, exp=0x88c46d8, 
     pos=0xbfffcdc4, noside=EVAL_NORMAL) at eval.c:71
 #17 0x080f4b3c in evaluate_subexp_standard (expect_type=0x0, exp=0x88c46d8, 
     pos=0xbfffcdc4, noside=EVAL_NORMAL) at eval.c:1854
 #18 0x080eff42 in evaluate_subexp (expect_type=0x0, exp=0x88c46d8, 
     pos=0xbfffcdc4, noside=EVAL_NORMAL) at eval.c:71
 #19 0x080f4b3c in evaluate_subexp_standard (expect_type=0x0, exp=0x88c46d8, 
     pos=0xbfffcdc4, noside=EVAL_NORMAL) at eval.c:1854
 #20 0x080eff42 in evaluate_subexp (expect_type=0x0, exp=0x88c46d8, 
     pos=0xbfffcdc4, noside=EVAL_NORMAL) at eval.c:71
 #21 0x080f0119 in evaluate_expression (exp=0x88c46d8) at eval.c:161
 #22 0x0810198c in set_command (
     exp=0x88c430c "$esp=$marcel_saved_sp, $ebp=$marcel_saved_bp,
 $eip=$marcel_saved_pc", from_tty=0) at printcmd.c:999
 #23 0x080bae63 in do_cfunc (c=0x831f1d8, 
     args=0x88c430c "$esp=$marcel_saved_sp, $ebp=$marcel_saved_bp,
 $eip=$marcel_saved_pc", from_tty=0) at cli/cli-decode.c:57
 #24 0x080bd2ac in cmd_func (cmd=0x831f1d8, 
     args=0x88c430c "$esp=$marcel_saved_sp, $ebp=$marcel_saved_bp,
 $eip=$marcel_saved_pc", from_tty=0) at cli/cli-decode.c:1599
 #25 0x080851ba in execute_command (p=0x88c434e "c", from_tty=0) at
 top.c:733
 #26 0x080bd905 in execute_control_command (cmd=0x839d600)
     at cli/cli-script.c:316
 #27 0x080bd841 in execute_user_command (c=0x839d708, args=0x0)
     at cli/cli-script.c:279
 #28 0x0808511d in execute_command (p=0x88c448a "", from_tty=0) at
 top.c:725
 #29 0x080bd905 in execute_control_command (cmd=0x839d7d8)
     at cli/cli-script.c:316
 #30 0x080bdb0a in execute_control_command (cmd=0x839d770)
     at cli/cli-script.c:416
 #31 0x080bd841 in execute_user_command (c=0x839d818, args=0x0)
     at cli/cli-script.c:279
 #32 0x0808511d in execute_command (p=0x83098e8 "", from_tty=1) at
 top.c:725
 #33 0x0812843a in command_handler (command=0x83098e0 "rest-ctx")
     at event-top.c:500
 #34 0x08128bf0 in command_line_handler (rl=0x8364190 "8q\213\b")
 
 etc
 
 Regards,
 Samuel Thibault