Debugging

If you're at all like me, your debugging process is completely undisciplined. You throw in a few print statements when you need to figure out what's wrong. Then you delete them, only to add them again later. There are accepted methods of handling debugging. If you've ever peaked inside an open source project, you've probably seen a bit of debug code. Perhaps you're familiar with loggers and you've seen console debug output.

Asterisk uses multiple levels of debugger output. The more 'v's you add to the start options, the more debug output you get. The log statements usually look something like this. 

ast_log(LOG_NOTICE, "debug argument - %s\n",arg);
ast_log(LOG_WARNING, "debug statement\n");

These statements are scattered throughout the code base. They will execute depending on the debug level. Although there will be some performance penalty for having them in the production code, it won't be significant as long as they aren't placed deep in a loop. An advantage of this is that your end users can use debug output to troubleshoot. And even if a technical person needs to do the debugging, a carefully formatted string is often going to be more helpful than a core dump.

If you don't want to keep debug statements in code, you have a few options. You could just leave the print statements in and comment them out. Another trick I have seen is this. 

#if 0
    foo();
    printf("%d\n",total);
#endif

Then you just change one character when you want this code compiled in. You could also use an #ifdef and define the symbol only when debugging. This can be done from a makefile.

One trick that I have used is to conditionally compile a single line. 

#if 0
#  define DEBUG(statement) statement
#else
#  define DEBUG(statement) 
#endif

DEBUG(log("log output %s\n", str));

Again, 0 could be replaced with a symbol defined in a makefile. And the code will only be compiled in if the program is built in debug mode.

However you decide to handle debugging is fine. But you should make a conscious decision as to how it will be done, and try to stick with it and be consistent. It's a lot easier to change one symbol and recompile than to re-type the same print statements every time a problem comes up.


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