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* Re: Why does gdb implement 'next' command with a series of "vCont;s"?
@ 2007-07-30  8:14 congli
  2007-07-30 22:12 ` Posting from work/university addresses Jim Blandy
  0 siblings, 1 reply; 34+ messages in thread
From: congli @ 2007-07-30  8:14 UTC (permalink / raw)
  To: gdb

There is an error in my example. When I issue a 'next' command at
line 6, the step_range_end should be the first instruction of line 7,
0x8048372, not 804836f.

 >  I have a simple test program (x86 platform), debug it from
 >  a remote machine. First, let the program stop at line 6,
 >  then issue a 'next' command. I have set the 'debug remote'
 >  option, and the command line output is:
 >
 >  6           j = i + 1;
 >  (gdb) n
 >  Sending packet: $m45e2ca,1#8e...Ack
 >  Packet received: 55
 >  Sending packet: $M45e2ca,1:cc#6e...Ack
 >  Packet received: OK
 >  Sending packet: $m8048364,1#3b...Ack
 >  Packet received: c7
 >  Sending packet: $M8048364,1:cc#1b...Ack
 >  Packet received: OK
 >  Sending packet: $m464005,1#fd...Ack
 >  Packet received: 55
 >  Sending packet: $M464005,1:cc#dd...Ack
 >  Packet received: OK
 >  Sending packet: $m496014,1#02...Ack
 >  Packet received: 55
 >  Sending packet: $M496014,1:cc#e2...Ack
 >  Packet received: OK
 >  Sending packet: $vCont;s#b8...Ack
 >  Packet received: T0505:887a80bf;04:607a80bf;08:6e830408;
 >  Sending packet: $vCont;s#b8...Ack
 >  Packet received: T0505:887a80bf;04:607a80bf;08:6f830408;
 >  Sending packet: $vCont;s#b8...Ack
 >  Packet received: T0505:887a80bf;04:607a80bf;08:72830408;
 >  ...
 >
 >  this is the objdump of line 6 and line 7 of my program:
 >
 >     j = i + 1;
 >   804836b:	8b 45 f4             	mov    0xfffffff4(%ebp),%eax
 >   804836e:	40                   	inc    %eax
 >   804836f:	89 45 f8             	mov    %eax,0xfffffff8(%ebp)
 >      k = j + 1;
 >   8048372:	8b 45 f8             	mov    0xfffffff8(%ebp),%eax
 >   8048375:	40                   	inc    %eax
 >   8048376:	89 45 fc             	mov    %eax,0xfffffffc(%ebp)
 >
 >   As you can see, line 6 of my program consists of three assembly
 >   instructions. gdb implements the 'next' command by three "vCont;s",
 >   and stop at the first instruction of line 7, which address is
 >   0x8048372.
 >
 >   My question is, when I issue the 'next' command, gdb already
 >   know the 'step_range_end' is 0x804836f, why not implement the
 >   'next' command by set a breakpoint at 0x804836f and then issue
 >   "vCont;c"? When the program meet the breakpoint at 0x804836f,
 >   we can do a single "vCont;s" to the first instruction of
 >   line 7, 0x8048372.
 >
 >   This implementation of 'next' command will decrease network
 >   traffic and make the command more efficient, especially when
 >   there is a lot of assembly instructions within one C souce line.
 >   But why does gdb take the "vCont;s" method?
 >
 >   Thanks.
 >


^ permalink raw reply	[flat|nested] 34+ messages in thread

end of thread, other threads:[~2007-08-06 14:22 UTC | newest]

Thread overview: 34+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-07-30  8:14 Why does gdb implement 'next' command with a series of "vCont;s"? congli
2007-07-30 22:12 ` Posting from work/university addresses Jim Blandy
2007-07-31  0:08   ` Anmol P. Paralkar
2007-07-31  1:08     ` Christopher Faylor
2007-08-02 16:58       ` Robin Getz
2007-08-02 17:12         ` Robert Dewar
2007-08-02 17:42           ` Robin Getz
2007-08-02 18:09             ` Ian Lance Taylor
2007-08-04 17:36             ` Eric Weddington
2007-08-02 18:23           ` Jim Blandy
2007-08-02 18:34             ` Christopher Faylor
2007-08-03 12:05               ` Eli Zaretskii
2007-08-03 14:27                 ` Christopher Faylor
2007-08-03 14:39                 ` Ian Lance Taylor
2007-08-03 17:10                   ` Eli Zaretskii
2007-08-03 23:11                     ` Christopher Faylor
2007-08-04  8:41                       ` Eli Zaretskii
2007-08-04 18:36                         ` Ian Lance Taylor
2007-08-04 18:51                           ` Eli Zaretskii
2007-08-05  0:03                             ` Christopher Faylor
2007-08-05  3:51                               ` Robin Getz
2007-08-05  5:07                                 ` Christopher Faylor
2007-08-05 12:03                                   ` Robert Dewar
2007-08-05 18:27                                     ` Christopher Faylor
2007-08-06  6:53                                   ` Eli Zaretskii
2007-08-06 14:04                             ` Ian Lance Taylor
2007-08-06 14:22                               ` Eli Zaretskii
2007-08-04 20:04                           ` Bob Rossi
2007-08-05  0:06                             ` Christopher Faylor
2007-08-05  1:58                               ` Bob Rossi
2007-08-05  3:13                               ` Eli Zaretskii
2007-08-05  4:33                                 ` Christopher Faylor
2007-08-06 14:07                             ` Ian Lance Taylor
2007-07-31  7:59   ` Wenbo Yang

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