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POgetting different values when inspecting an object with gdb
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  1. POgetting different values when inspecting an object with gdb
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    copied!<p>I'm using gdb to debug a c++ program which terminated with a segmentation fault. Looking at the stack, the first few frames are:</p> <pre><code> #0 0x0041c496 in cDefaultList::doInsert (this=0x9c69708, obj=0x9c69348) at cdefaultlist.cc:119 #1 0x0041c86c in cDefaultList::take (this=0x9c69708, obj=0x9c69348) at cdefaultlist.cc:189 #2 0x0043bd9c in cPacket::encapsulate (this=0x9c69708, msg=0x9c69348) at cmessage.cc:589 #3 0x08448861 in MobIPv6mn::handleMessage (this=0x96d3350, msg=0x9c69348) at src/networklayer/numbatIPv6/mip6.cc:170 #4 0x0046069c in cSimulation::doOneEvent (this=0x87f3318, mod=0x96d3350) at csimulation.cc:627 #5 0x0015ecdf in Tkenv::doRunSimulation (this=0x87f3110) at tkenv.cc:529 #6 0x0015e899 in Tkenv::runSimulation (this=0x87f3110, mode=2, until_time=..., until_eventnum=0, until_msg=0x0, until_module=0x0) at tkenv.cc:402 #7 0x00168f10 in run_cmd (interp=0x8842e48, argc=2, argv=0xbfffcb00) at tkcmd.cc:430 </code></pre> <p>So I do:</p> <pre><code>frame 3 </code></pre> <p>and later want to inspect "msg" with <code>print * (IPv6 *) msg</code>, because that's what the type of msg should be. Well, when I look at the Ipv6-specific fields of msg, I always get completely different values, like:</p> <p><code>srcIP_var = {addr = "\000\000\000\000\000\000i\000\000\000\001\000\000\000\001"}, dstIP_var = { addr = "\000\000H\223\306\t\000\000\000\000\000\000\000\000\000"}, BindingUpdate_var = false, BindingAck_var = false, Dhcpv6Relay_var = false}</code></p> <p>or </p> <p><code>srcIP_var = {addr = "\000\000\000\000\000\000)\000\000\000\020\264K\000\020\264"}, dstIP_var = {addr = "\346\t:SCALEEXP_UNIN"}, BindingUpdate_var = 73, BindingAck_var = 84, Dhcpv6Relay_var = 73}</code></p> <p>or even:</p> <p><code>srcIP_var = {addr = "\000\000\000\000\000\000\061\000\000\000\030\264K\000\030\264"}, dstIP_var = { addr = "K\000\a\350N\v\304\350N\v\001\000\000\000\001"}, BindingUpdate_var = false, BindingAck_var = false, Dhcpv6Relay_var = false} </code></p> <p>Why is that? Does that mean the packet is not really of the type I tried to cast it to?</p> <p>Thanks a lot!</p>
 

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