Debugging options

There are a couple of compilation options to help with debugging HANDE.

• The -g option to tools/mkconfig.py enables compiler options for warnings and run-time checking.

• The -DDEBUG preprocessor flag enables additional debugging output. Currently this is stack traces when stop_all is called to terminate with an error - the addresses given can be converted to file:line number information with addr2line. For example:

  $ /path/to/hande.x test.lua
  [...]
  /usr/lib/libasan.so.4(+0x55c60)[0x7fc1c5000c60]
  ./bin/hande.x(+0x609e80)[0x5614f6742e80]
  ./bin/hande.x(+0x469177)[0x5614f65a2177]
  ./bin/hande.x(+0x1aa839)[0x5614f62e3839]
  ./bin/hande.x(+0x1aa8f1)[0x5614f62e38f1]
  /usr/lib/libc.so.6(__libc_start_main+0xea)[0x7fc1c17e1f4a]
  ./bin/hande.x(+0xa93ca)[0x5614f61e23ca]
  
  ERROR.
  HANDE stops in subroutine: run_hande_lua.
  Reason: File does not exist:test.lua
  EXITING...
  

  The addresses are not conserved between builds, compilers, optimisation levels and so on. The filenames can be included if -rdynamic is included in the linker flags:

  /usr/lib/libasan.so.4(+0x55c60)[0x7f1943b93c60]
  ./bin/hande.x(__errors_MOD_stop_all+0x1c2)[0x55bf6aae5d30]
  ./bin/hande.x(__lua_hande_MOD_run_lua_hande+0x6e1)[0x55bf6a945027]
  ./bin/hande.x(+0x1c66e9)[0x55bf6a6866e9]
  ./bin/hande.x(main+0x36)[0x55bf6a6867a1]
  /usr/lib/libc.so.6(__libc_start_main+0xea)[0x7f1940374f4a]
  ./bin/hande.x(_start+0x2a)[0x55bf6a58527a]
  
  ERROR.
  HANDE stops in subroutine: run_hande_lua.
  Reason: File does not exist:test.lua
  EXITING...
  

  The actual source (file and linenumber) can be found using either addr2line or gdb (easier). With addr2line:

  $ addr2line +0x469177 -e /path/to/hande.x
  /home/james/hande/src/hande-bug-fix/src/lua_hande.F90:92
  

  and with gdb:

  $ gdb /path/to/hande.x
  (gdb) list *__lua_hande_MOD_run_lua_hande+0x6e1
  0x485027 is in lua_hande::run_lua_hande (src/lua_hande.F90:92).
  87
  88                    ! Read input file on parent and broadcast to all other processors.
  89                    if (parent) then
  90                        call get_command_argument(1, inp_file)
  91                        inquire(file=inp_file, exist=t_exists)
  92                        if (.not.t_exists) call stop_all('run_hande_lua','File does not exist:'//trim(inp_file))
  93
  94                        write (6,'(a14,/,1X,13("-"),/)') 'Input options'
  95                        call read_file_to_buffer(buffer, inp_file)
  96                        write (6,'(A)') trim(buffer)
  

  where __lua_hande_MOD_run_lua_hande+0x6e1 was the address of interest from the stacktrace. Note the * prefix. The same can be done with just the bare address if -rdynamic isn’t used.

  addr2line is a little more involved if -rdynamic is used – one needs to find the offset for the function of interest and hence find the line address by adding the address relative to the function start. For example, in:

  ./bin/hande.x(__errors_MOD_stop_all+0x1c2)[0x55bf6aae5d30]
  

  the function is __errors_MOD_stop_all (stop_all in the errors module). The start address can be found from objdump:

  $ objdump -T /path/to/hande.x | grep __errors_MOD_stop_all
  0000000000625b6e g    DF .text    0000000000000c0c  Base        __errors_MOD_stop_all
  

  The first field is the address in hexadecimal. Hence:

  $ python -c 'print(hex(0x0000000000625b6e+0x1c2))'
  0x625d30
  $ addr2line -e /path/to/hande.x 0x625d30
  /path/to/hande/lib/local/error_handling.F90:60
  

  Note the explicit 0x prefix for the start address of __errors_MOD_stop_all.