How to interpret GDB backtrace of an OCaml program?

Question

I'm trying to read the backtrace of my OCaml program inside GDB. The output looks like the following:

(gdb) bt
#0  0x0000000100535ac6 in .L207 ()
#1  0x0000000100535acb in .L207 ()
#2  0x0000000100535acb in .L207 ()
...

How can I interpret this kind of output?

EDIT:

• I've enabled debug info by using ./configure --enable-debug (I'm using oasis).
• I'm using GDB 7.9.1 on OS X 10.10
• I'm using OCaml 4.02.2

EDIT 2: the output seems to be correct with the Linux version of GDB. Does anyone know why there is such a difference between the OS X and Linux versions?

Answer 1

Did you compile with -g? I typically get stuff like #3 0x0000000000401f49 in caml_program () . There's also export OCAMLRUNPARAM=b , gives stacktraces when your program crashes.

(You might want to post a code snippet and the compile commands.)

You may also find http://www.ocamlpro.com/blog/2012/08/20/ocamlpro-and-4.00.0.html and http://oud.ocaml.org/2012/slides/oud2012-paper5-slides.pdf handy.

Answer 2

Check what C compiler and assembler is used. Mac OS probably uses clang and it may not generate full debug info for gdb . In that case using lldb may be more fruitful.

Answer 3

Have you looked into using ocamldebug instead, or do you have to debug on the machine end?

If you want to understand what your code is doing on the CPU/Register/Assembly/Bitfiddling-witchcraft end then it might be more informative to read Jane Street's blog post writing performance sensitive ocaml code .