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Software Breakpoints in the IDE

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How convenient would it be to do something like this:

<syntaxhighlight lang="c">

if (some_assertion_failure) {
halt_the_target_in_a_spin_loop_so_i_can_see_the_processor_state()
}

</syntaxhighlight>

Typically we think of breakpoints as IDE-only i.e. we manually have to set BPs at certain locations. However it would be neat to programmatically trigger a breakpoint. Naturally we can do this with AET but not every chip has AET capabilities.

The good news is we can do this with the software breakpoint opcode - each TI Instruction Set Architecture has one. Here is some code we use to apply programmatic software breakpoints

<syntaxhighlight lang="c">

/*

* ======== UTL_assert ========
* Assert macro for exceptions
*
* If an assertion fails, we interrupt the execution flow and preserve
* the state of the system.
* If the application is being debugged with Code Composer Studio, we place
* a word in program memory that has the effect of a breakpoint -- it halts
* the execution and CCS shows the line of code where the failed assertion
* occurred. The special word that causes the breakpoint effect is different
* for every DSP family.
* Otherwise, if CCS is not used, we disable interrupts and run into an
* infinite loop, waiting for the user to halt the target manually.
* To do so, define UTL_ASSERTCCS macro flag externally to be 0.
*/
  1. if UTL_ASSERT == 1 /* first check if UTL_ASSERT() is enabled at all */
/*
* First we define the special word for each platform:
* On 55x we add a NOP to guard against small possibility that
* long instruction pipeline causes debugger to stop at next C src line
* instead of currently executing C src statement. We also ensure this
* works on both 55x mnemonic (default) and algebraic 55x assembler.
* Note that asm statement is a single execution context to maintain
* pre-processor consistency.
*/
#if defined( _54_ )
#define UTL_STOPWORD asm( " ESTOP" )
#elif defined( _55_ )
#define UTL_STOPWORD asm(" ;\n .if (.MNEMONIC)\n ESTOP_1\n .else\n ESTOP_1()\n .endif\n NOP")
#elif defined(_64P_) /* Joule */
#define UTL_STOPWORD asm( " SWBP 0")
#elif defined( _6x_ )
#define UTL_STOPWORD asm( " NOP\n .word 0x10000000" )
#else
#define UTL_ASSERTCCS 0 /* unknown platform => no CCS breakpoint */
#endif
#if !defined( UTL_ASSERTCCS )
#define UTL_ASSERTCCS 1
#endif
/* check if it's OK with the user to use CCS breakpoints for asserts() */
#if UTL_ASSERTCCS == 1
/* it is; define the UTL_assert macro */
#define UTL_assert( expr ) \
for (; !( expr ); ) \
UTL_STOPWORD
#else /* UTL_ASSERTCCS == 0 */ /* no Code Composer Studio here */
#define UTL_assert( expr ) do { \
if ( !(expr) ) { /* use UTL_error() to halt, prototyped below */ \
UTL_error( "Assertion Violation: " __FILE__ ", line " \
UTL_stringify(__LINE__) " (" UTL_stringify(expr) ")", 0 ); \
} \
} while (0)
#endif /* UTL_ASSERTCCS */
/*
* UTL_assertFunc() is meant for testing expressions with side effects,
* i.e. mostly for checking function calls. If enabled, behaves exactly
* the same as UTL_assert. If disabled, it is not expanded to nothing
* but to actual expression. E.g.,
* UTL_assertFunc( someFunc() == TRUE );
* If asserts are disabled, expands to
* (someFunc() == TRUE);
*/
#define UTL_assertFunc UTL_assert
  1. else /* UTL_ASSERT */
#define UTL_assert( expr )
#define UTL_assertFunc( expr ) (expr)
  1. endif /* UTL_ASSERT */

</syntaxhighlight>

This code shows the mnemonic / opcode for the different ISAs. You can use the UTL_assert() macro or just the UTL_STOPWORD definition.

Typical usage might be: <syntaxhighlight lang="c">

mbxProcess = MBX_create(sizeof(CtrlMsg), THRPROCESS_MBXLENGTH, NULL);
UTL_assert( mbxProcess != NULL ); // halt the target and debug if we fail

</syntaxhighlight>

For the C28x devices, the software breakpoint instruction is: asm( "ESTOP0")


This capability is also being considered for the simulator - the enhancement number is SDSCM00025430.

Another topic to look at is Simulator Data Breakpoints and Watchpoints. However this feature is not available on all ISAs.