marktseng / libunwind-examples

A few libunwind examples

libunwind examples

A few libunwind examples:

• backtrace.cpp --- shows a demangled backtrace.
• more to come ...

Build instructions

On OSX, you should be able to just build as is. On other systems, you need to link with -lunwind. You also need cxxabi.h, part of libstdc++.

I've used -O0 for the examples, because llvm is surprisingly good at doing tail call elimination.

Example: backtrace.cpp

Shows how to print a backtrace.

You can double check that it works with gdb or lldb:

$ make backtrace
$ gdb ./backtrace
GNU gdb (GDB) 7.9.1
...
(gdb) break backtrace
Breakpoint 1 at 0x40086e: file backtrace.cpp, line 17.
(gdb) r
Starting program: .../backtrace

Breakpoint 1, backtrace () at backtrace.cpp:17
17        unw_getcontext(&context);
(gdb) bt
#0  backtrace () at backtrace.cpp:17
#1  0x0000000000400a02 in fac (n=0) at backtrace.cpp:51
#2  0x0000000000400a16 in fac (n=1) at backtrace.cpp:54
#3  0x0000000000400a16 in fac (n=2) at backtrace.cpp:54
#4  0x0000000000400a16 in fac (n=3) at backtrace.cpp:54
#5  0x0000000000400a16 in fac (n=4) at backtrace.cpp:54
#6  0x0000000000400a16 in fac (n=5) at backtrace.cpp:54
#7  0x0000000000400a16 in fac (n=6) at backtrace.cpp:54
#8  0x0000000000400a16 in fac (n=7) at backtrace.cpp:54
#9  0x0000000000400a16 in fac (n=8) at backtrace.cpp:54
#10 0x0000000000400a16 in fac (n=9) at backtrace.cpp:54
#11 0x0000000000400a16 in fac (n=10) at backtrace.cpp:54
#12 0x0000000000400a2a in main () at backtrace.cpp:60
(gdb) c
Continuing.
#1  0x0000000000400a02 sp=0x00007fffffffd7b0 fac(int) + 0x16
#2  0x0000000000400a16 sp=0x00007fffffffd7d0 fac(int) + 0x2a
#3  0x0000000000400a16 sp=0x00007fffffffd7f0 fac(int) + 0x2a
#4  0x0000000000400a16 sp=0x00007fffffffd810 fac(int) + 0x2a
#5  0x0000000000400a16 sp=0x00007fffffffd830 fac(int) + 0x2a
#6  0x0000000000400a16 sp=0x00007fffffffd850 fac(int) + 0x2a
#7  0x0000000000400a16 sp=0x00007fffffffd870 fac(int) + 0x2a
#8  0x0000000000400a16 sp=0x00007fffffffd890 fac(int) + 0x2a
#9  0x0000000000400a16 sp=0x00007fffffffd8b0 fac(int) + 0x2a
#10 0x0000000000400a16 sp=0x00007fffffffd8d0 fac(int) + 0x2a
#11 0x0000000000400a16 sp=0x00007fffffffd8f0 fac(int) + 0x2a
#12 0x0000000000400a2a sp=0x00007fffffffd910 main + 0xe
#13 0x0000003a7101ed5d sp=0x00007fffffffd920 __libc_start_main + 0xfd
#14 0x00000000004007a9 sp=0x00007fffffffd9e0 _start + 0x29

Interesting pointers

• "Deep Wizardry: Stack Unwinding", http://blog.reverberate.org/2013/05/deep-wizardry-stack-unwinding.html

License

Made by Christian Stigen Larsen in 2016
Put in the public domain.