Debugging system: ideas on how to improve the debugging system

Table of Contents Current state Future ideas and alternatives Makefile approach Global debug.h and debug_arch.h debug.h module.c Individual debug_xxx.h and debug_arch.h Global debug variable

Current state

Currently debugging is turned on and off in every file separately.

The only way to enable DEBUG for the module is to set DEBUG to 1 or something other than 0 within the code of the module. There are also some modules within contiki where DEBUG is set to 1 in the release version, looks like someone forgot to set it back to 0 again:

user@machine:~/workspace/contiki-2.6$ fgrep " DEBUG 1" * -r
core/net/mac/ctdma_mac.c:#define DEBUG 1
...
platform/redbee-dev/contiki-mc1322x-main.c:#define DEBUG 1

Future ideas and alternatives

Makefile approach

• Uses top level makefile.include to recompile specified modules with a DEBUG=1 or DEBUG=0 switch. The names of DEBUG=1 modules are stored in a text file in the $OBJECT directory. Example:

 $make TARGET=avr-raven DEBUG="rpl-dag.c,sicslowpan.c"
 avr-gcc -DEBUG=1 ... rpl-dag.c
 avr-gcc -DEBUG=1 ... sicslowpan.c
 ...
 $make TARGET=avr-raven DEBUG=rpl-dag.c
 avr-gcc ... -DEBUG=0 sicslowpan.c
 ...
 $make TARGET=avr-raven
 avr-gcc ... -DEBUG=0 rpl-dag.c

+ Full recompile not needed
- Not as portable? More cumbersome than include files?

Opinions:

• Useless if build system is not GNU build system --marcas 22:31, 12 July 2012 (CEST)
• Minimal change to existing source, breaks nothing if not used.
• Not one byte of debug system in the final binary if DEBUG is disabled --marcas 15:54, 13 July 2012 (CEST)

Global debug.h and debug_arch.h

This method extends the current implementation used in contiki 2.6 . The idea behind it is to move the definition of the used debug output function into a global debug.h file. Also other switches are defined in the debug.h file, allowing one to switch on or off different modules for debugging. The main drawback : All modules that include debug.h have to recompiled if a change is performed in debug.h.

debug.h

This file includes all definitions for debug handling:

• The debug output function (DBG_FUNC), which has to be a varargs function. This function has to use the printf signature ... this allows one to write an output function for any output device (uart,spi,i2c,tcp/ip ...).
• The on/off switches for the modules

 #ifndef DEBUG_H
 #define DEBUG_H
 
 /* Debugging output function (printf or any other var args function) */
 #if DEBUG
 #include <stdio.h>
 #define DBG_FUNC(...) printf(__VA_ARGS__)
 #else
 #define DBG_FUNC(...)
 #endif /* DEBUG */

 /* Following DEBUG check allows to write more complex debug sections beyond DBG("Debugmessage: %d",var). */
 /* But try to avoid more complex debug sections, for the readability of the code and run time issues (real time)! */
 #if DEBUG 

 /* application modules */
 #define DEBUG_MAIN              1
 
 /* NETSTACK modules */
 #define DEBUG_NETSTACK_RADIO    0 
 #define DEBUG_NETSTACK_RDC      0 
 #define DEBUG_NETSTACK_MAC      0 
 #define DEBUG_NETSTACK_NETWORK  0 
 #define DEBUG_NETSTACK_FRAMER   0  
 
 /* core/sys modules */
 /* ... */

 #endif /* DEBUG */
 
 #endif /* DEBUG_H */

module.c

The module can be enabled for debugging in debug.h.

If the module is disabled for debugging, the DBG - function is defined as empty, and thus not compiled into the module.

 #include <stdlib.h>
 #include "debug.h"
 
 #if DEBUG_MAIN
 #define DBG(...) DBG_FUNC(__VA_ARGS__)
 #else
 #define DBG(...)
 #endif
 
 int 
 main(void) 
 {
       DBG("This is a simple debug message!\n");

 #if DEBUG_MAIN
       {
         int dbg_test;
         DBG("This is a more complex debug message! - ");
         for(dbg_test = 0; dbg_test < 5; dbg_test++) {
           DBG("%d ", dbg_test); 
         }
         DBG("\n");
       }
 #endif /* DEBUG_MAIN */

       return EXIT_SUCCESS;
 }

+ Simple, portable  
- Full recompile

Opinions:

• The cost of the full recompile might be reduced by ccache --Morty 21:36, 12 July 2012 (CEST)
• Not one byte of debug system in the final binary if DEBUG is disabled --marcas 15:54, 13 July 2012
• Unless the file is generated this is likely to fail, because it must be actively maintained. ---Morty 2012/08/06 13:55//
• debug.h - maintenance only required if the main DEBUG switch is enabled. Disabled by default in release. --marcas 16:25, 06 August 2012
• Removed C99-only parts completly, as it also has to work with C89 syntax - Reason: Coding rules and low level C compilers and preprocessors --marcas 19:34, 15 August 2012
• As only one NETSTACK may be used at one time, there is no need for specific NETSTACK debug switches (e.g. DEBUG_XMAC and so on) --marcas 7:27, 12 October 2012

Individual debug_xxx.h and debug_arch.h

+ Portable, full recompile not needed
- Many debug_xxx.h files

Opinions:

• Not one byte of debug system in the final binary if DEBUG is disabled --marcas 15:54, 13 July 2012 (CEST)

Global debug variable

+ Simple, portable, full recompile not needed
- Increased memory use

Opinions:

• This will not work on your average sensor mote. --Morty 21:36, 12 July 2012 (CEST)