83 lines
3.0 KiB
Plaintext
83 lines
3.0 KiB
Plaintext
@node Troubleshooting
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@chapter Troubleshooting
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This chapter posts some information about possibly common errors in building
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or running ns-3 programs.
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Please note that the wiki (@uref{http://www.nsnam.org/wiki/index.php/Troubleshooting}) may have contributed items.
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@node Build errors
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@section Build errors
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@node Run-time errors
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@section Run-time errors
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Sometimes, errors can occur with a program after a successful build. These
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are run-time errors, and can commonly occur when memory is corrupted or
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pointer values are unexpectedly null.
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Here is an example of what might occur:
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@verbatim
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ns-old:~/ns-3-nsc$ ./waf --run tcp-point-to-point
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Entering directory `/home/tomh/ns-3-nsc/build'
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Compilation finished successfully
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Command ['/home/tomh/ns-3-nsc/build/debug/examples/tcp-point-to-point'] exited with code -11
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@end verbatim
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The error message says that the program terminated unsuccessfully, but it is
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not clear from this information what might be wrong. To examine more
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closely, try running it under the @uref{http://sources.redhat.com/gdb/,,gdb debugger}:
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@verbatim
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ns-old:~/ns-3-nsc$ ./waf --run tcp-point-to-point --command-template="gdb %s"
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Entering directory `/home/tomh/ns-3-nsc/build'
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Compilation finished successfully
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GNU gdb Red Hat Linux (6.3.0.0-1.134.fc5rh)
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Copyright 2004 Free Software Foundation, Inc.
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GDB is free software, covered by the GNU General Public License, and you are
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welcome to change it and/or distribute copies of it under certain conditions.
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Type "show copying" to see the conditions.
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There is absolutely no warranty for GDB. Type "show warranty" for details.
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This GDB was configured as "i386-redhat-linux-gnu"...Using host libthread_db library "/lib/libthread_db.so.1".
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(gdb) run
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Starting program: /home/tomh/ns-3-nsc/build/debug/examples/tcp-point-to-point
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Reading symbols from shared object read from target memory...done.
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Loaded system supplied DSO at 0xf5c000
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Program received signal SIGSEGV, Segmentation fault.
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0x0804aa12 in main (argc=1, argv=0xbfdfefa4)
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at ../examples/tcp-point-to-point.cc:136
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136 Ptr<Socket> localSocket = socketFactory->CreateSocket ();
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(gdb) p localSocket
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$1 = {m_ptr = 0x3c5d65}
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(gdb) p socketFactory
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$2 = {m_ptr = 0x0}
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(gdb) quit
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The program is running. Exit anyway? (y or n) y
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@end verbatim
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Note first the way the program was invoked-- pass the command to run as
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an argument to the command template "gdb %s".
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This tells us that there was an attempt to dereference a null pointer
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socketFactory.
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Let's look around line 136 of tcp-point-to-point, as gdb suggests:
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@verbatim
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Ptr<SocketFactory> socketFactory = n2->QueryInterface<SocketFactory> (Tcp::iid);
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Ptr<Socket> localSocket = socketFactory->CreateSocket ();
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localSocket->Bind ();
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@end verbatim
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The culprit here is that the return value of QueryInterface is not being
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checked and may be null.
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Sometimes you may need to use the @uref{http://valgrind.org,,valgrind memory
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checker} for more subtle errors. Again, you invoke the use of valgrind
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similarly:
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@verbatim
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ns-old:~/ns-3-nsc$ ./waf --run tcp-point-to-point --command-template="valgrind %s"
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@end verbatim
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