Trace

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To assist with debugging of XINU modules a standard trace interface is currently being implemented across the subsystems. Each module should have its own trace macro of the following form:

 #define [MODULE]_TRACE(...)     { \
           fprintf(TTY1, "%s:%d (%s) ", __FILE__, __LINE__, __FUNCTION__); \ 
           fprintf(TTY1, __VA_ARGS__); \
           fprintf(TTY1, "\n"); }

The trace macro should be defined within the subsystem's main header file. For example, the TTY driver would have the trace macro TTY_TRACE defined in tty.h.

To disable tracing for a particular module, the trace macro definition can be succeeded by:

 #undef [MODULE]_TRACE
 #define [MODULE]_TRACE

This redefines a particular module's trace macro as nothing, causing the C preprocessor to replace all calls to the module's trace function with nothing. This ability to easily remove trace calls from the module's code will reduce the size of XINU boot image when debugging using trace is not needed.

The overarching XINU_TRACE constant (defined in kernel.h) enables trace for any module with a trace macro defined. To allow all tracing to be disabled at once, each modules trace function should check if XINU_TRACE is defined and only define [MODULE]_TRACE as the trace macro if XINU_TRACE is defined. A full implementation of a [MODULE]_TRACE macro should be:

 #ifdef XINU_TRACE
   #define [MODULE]_TRACE(...)     { \
             fprintf(TTY1, "%s:%d (%s) ", __FILE__, __LINE__, __FUNCTION__); \ 
             fprintf(TTY1, __VA_ARGS__); \
             fprintf(TTY1, "\n"); }
 #else
   #define [MODULE]_TRACE
 #endif
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