Debugging – Some Useful Macros

---

Assert(3)

· Usage:

#include <assert.h>

void assert(scalar expression);

· Use assert religiously any time you know certain relationships that MUST hold between variables to another or a variable to a constant.

· It is helpful for the programmer, not the user.

o Sample output: “Assertion failed in file foo.c, function do_bar, line 1287”.

· Leave in your code FOREVER

o If symbol NDEBUG is defined, the macro goes to nothing.

Simple TRACE macro

• Useful so your fprintf(stderr,…) is not hard-coded in your code
• Basically what is present in MS Visual Studio C++ (and many other compilers no doubt…)
• Code: trace.h

More Complex DEBUG Macro

• Debug flags setup from the (very portable and widely used) SR Language (courtesy of Gregg Townsend)
• Idea:

• TRACE gives you EVERY output ALL THE TIME.
• This debug macro setup lets you turn on and of individual debug “topics” (up to 32) – MUCH finer-grained control over the debug output
• Implementation: have a debug flag bit array set at runtime in an environment variable to change what debug printouts happen without recompiling your code
• Also can have other information printed out on the debug line before the debug statement (thread ID, thread state, …)

• Usage:

• Template: DEBUG(FLAGS, FORMAT, a1, a2, a3);
• Real example: DEBUG (D_SPAWN, "r%06lX spawn p%06lX", CUR_RES, pr, 0);
• Can also use multiple flags in code: DEBUG(D_FLAG2|D_FLAG2, …)
• Must first initialize at startup by calling sr_init_debug()
• Code (note: details not testable (they are hairy!), main ideas/benefits are): debug.h, debug.c

• Note: it was coded before __VA_ARGS__ was defined for macros, but for portability they would still probably use this version

---