Troubleshooting

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Platform-specific issues

Cygwin

Python bindings

Python bindings do not build successfully due to a gccxml bug. See the NS-3_Python_Bindings#Caveats page.

If you see "resolving vtable" messages while linking such as the below when you compile on Cygwin, you can safely ignore them:

[530/535] cxx_link: build/debug/examples/wifi-wired-bridging_23.o -> build/debug
/examples/wifi-wired-bridging.exe
Info: resolving vtable for ns3::EmptyAttributeValueby linking to __imp___ZTVN3ns
319EmptyAttributeValueE (auto-import)
Info: resolving vtable for ns3::RandomVariableValueby linking to __imp___ZTVN3ns
319RandomVariableValueE (auto-import)
Info: resolving vtable for ns3::RectangleValueby linking to __imp___ZTVN3ns314Re
ctangleValueE (auto-import)
Info: resolving vtable for ns3::TimeValueby linking to __imp___ZTVN3ns39TimeValu
eE (auto-import)
Info: resolving vtable for ns3::BooleanValueby linking to __imp___ZTVN3ns312Bool
eanValueE (auto-import)

etc.

NSC

The Network Simulation Cradle is not supported under Cygwin. It is advised to use a Unix-based platform instead. Windows users can use a virtual machine to run e.g. Linux. See e.g. http://www.virtualbox.org/ for a free virtual machine.

General build problems

• Q. What is this kind of build error representative of?

 assert failed. file=../src/core/type-id.cc, line=389, cond="uid != 0"
 Command ['/ns-3-dev/build/debug/examples/mixed-wireless'] exited with code -5

• A. The system can't find the specified TypeId. Check spelling, and whether it is prefixed with the namespace "ns3::"
• Q. A required software package is in a non-standard place. How to get waf to find the packages?
• A. To compile with non-standard link path, use the environment variable LINKFLAGS. Example for bash shell:

LINKFLAGS="-L/tmp" ./waf configure

Run-time errors

• Q. What is this assertion indicating?

 assert failed. file=debug/ns3/tags.h, line=105, cond="sizeof (T) <= Tags::SIZE"

• A. The packet tag may be greater than Tags::SIZE (16 bytes)

• Q. Why does valgrind fail with SIGILL on a simulation using NSC?
• A. Valgrind does not work under 64-bit mode when running NSC due to lack of support for all the opcodes used. This has been confirmed to work in 32-bit mode. Check this bug report if you are concerned about a possible valgrind failure with an nsc script and want to see if it is a known issue.

• Q. NSC does not work on a platform with SELinux enabled; for instance

 $ ./waf --run tcp-nsc-lfn
 Entering directory `/hg/ns-3-dev/build'
 [250/250] build-nsc
 Compilation finished successfully 
 /hg/ns-3-dev/build/debug/liblinux2.6.26.so: cannot restore segment
 prot after reloc: Permission denied
 Command ['/hg/ns-3-dev/build/debug/examples/tcp-nsc-lfn'] exited
 with code -11 

• A. This is logged in the tracker. Workaround: to temporarily disable enforcement on a running system, set

 /usr/sbin/setenforce 0

To permanently disable enforcement during a system startup change "enforcing" to "disabled" in /etc/selinux/config and reboot.

• Q. What happened to my pcap trace files? The files are empty or are missing some packets!
• A. This is usually a symptom of a memory leak; the pcap trace files do not close cleanly. Try running your script with the --valgrind option to see if you've introduced a memory leak.

Debugging tips

• Q. Is there a way to dereference a Ptr when in gdb?
• A. yes: p *ptr->m_ptr